DATE: Jan 9
SPEAKER:Tom Timusk
ORGANIZATION:McMaster University

Evidence of a quantum critical point in the phase diagram of the overdoped high temperature superconductors

The mechanism that leads to high temperature superconductivity in the doped copper oxides is still not known. A central issue is the nature of the phase diagram of oxygen doping vs. temperature. As first emphasized by Anderson, the striking two-dimensionality of the crystal structure leads to an anomalous normal state. It has been suggested recently that strong quantum fluctuations in this state could lead to a zero temperature quantum critical point. I report on recent evidence for such a critical point in crystals of overdoped cuprates with a superconducting Tc of 60 K. At this critical concentration there is evidence of quantum disorder down to 10 K temperature as shown by a linear variation of the inverse lifetime of the carriers with temperature and frequency. On each side of this critical doping are two coherent phases: on the low doping side a gapped phase and on the high doping side a coherent phase without a gap. All the phases are superconducting at low temperature. The presentation will be introductory and I will not assume any previous knowledge of either high temperature superconductivity.

DATE: Jan 16
SPEAKER:Dan Watson
ORGANIZATION:University of Rochester

Star Formation with the Space Infrared Telescope Facility (SIRTF)

SIRTF, the fourth of NASA's Great Observatories in space, will be launched into heliocentric orbit in mid-July 2002, and begin its five year mission as the world's premiere infrared observatory. I will describe briefly the SIRTF satellite, telescope, instruments and scientific goals. The potential major advances the facility will make will be illustrated with a discussion of the aims of one of its major guaranteed-time programs, that on the genesis and evolution of stars and planetary systems in our galaxy.

DATE: Jan 23
SPEAKER:Christine Wilson
ORGANIZATION:McMaster University

A Close-Up View of a Galaxy Merger: Molecular Gas and Star Formation in the "Antennae"

As the closest example of a merger of two massive spiral galaxies, the "Antennae" system (NGC 4038/39) offers a unique opportunity to study the physical and dynamical properties of the interstellar medium in an active merger system. The Antennae have one of the largest populations of luminous star clusters known, while observations with the Infrared Space Observatory have revealed luminous regions of massive star formation that are completely invisible at optical wavelengths. Studying the properties of the molecular gas out of which these star clusters formed is important for understanding the triggering of intense star formation in galaxy mergers. I will present new observations of the Antennae in CO emission which reveal extremely massive concentrations of molecular gas, a chaotic velocity field, and evidence for cloud collisions near the strongest mid-infrared peak. It seems likely that the formation of the luminous star clusters takes place in these massive gas concentrations, while cloud-cloud collisions may provide an explanation for the unusually mid-infrared strong source.

DATE: Jan 30
SPEAKER:Robert Brooks
ORGANIZATION:University of Guelph

Over 100 Years of Spectroscopy with Helium

Since the year 2000 celebrates 100 years of quantum physics it may be appropriate to take an historical look at a subject in which Canadians have figured prominently. I shall review the early history of helium from its discovery in the solar spectrum (hence its name) in 1868, and its subsequent discovery on earth, through its role in the early applications of quantum mechanics. A selection of topics thereafter will demonstrate the breadth and continuing interest of helium spectroscopy.

DATE: Feb 6
SPEAKER:Robert Orr
ORGANIZATION:University of Toronto

What is the Universe made of?

At first sight the Universe appears to be made of "matter"; and we have a fairly good understanding of this matter. The basic building blocks are quarks and leptons; and a rather well understood theory describes how these particles interact via the strong, weak, and electromagnetic forces. However, there is evidence that this "matter" only constitutes 5% of the mass of the universe. Another 35% may consist of unobserved forms of matter, "dark matter". The remaining 60% of the mass of the Universe seems to be "dark energy"; energy associated with the vacuum, which may be causing the expansion of the Universe to accelerate. What we have so far observed and understood may actually be a rather minor aspect of the Universe. I will talk about some of these ideas, and describe experiments, which U of T people are involved in, which may actually produce the particles of "dark matter", and throw light on the origin of mass, and of the energy associated with the vacuum.

DATE: Feb 13
SPEAKER:originally scheduled reading week
ORGANIZATION:AFFILIATION

NO COLLOQUIUM

ABSTRACT

DATE: Feb 20
SPEAKER:Henk Hoekstra
ORGANIZATION:CITA & Department of Astronomy, University of Toronto

Looking at the dark side

Since the discovery of the first gravitational lens in 1979 a whole new and exciting field in astronomy has developed. In this talk I will discuss one of the recent applications of gravitational lensing: weak lensing. Early applications were mainly limited to the study of the mass distribution of clusters of galaxies, of which I will give some examples. Currently, like the rest of observational cosmology, we are moving into a new era of high precision measurements of the cosmological parameters,in which weak lensing also plays an important role. I will present some of the latest results from large imaging surveys, and discuss what we hope to achieve in the coming years

DATE: Feb 27
SPEAKER:John Sipe
ORGANIZATION:University of Toronto

Quantum interference and coherent current control

For optical excitation at energies above the band gap of a semiconductor or insulator, qualitatively new nonlinear optical phenomena appear. Macroscopic currents can actually be injected involving average electron velocities of hundreds of kilometres per second. The electrons and holes acquire their energy from the photons, but their momentum from the crystal lattice. The effect can be understood as arising from a quantum interference between different pathways leading to absorption. Such phenomena appear both in crystals that lack centre-of-inversion symmetry and in those that do not, but in qualitatively different ways. A new generalization of this effect offers the promise of the coherent control of spins in semiconductors. Other possible applications include phase measurements of ultra-short pulses. Both theory and experiment will be reviewed.

DATE:Mar 6
SPEAKER:Victoria Kaspi
ORGANIZATION:McGill University

CAP LECTURE: Diversity in Young Neutron Stars

Since the discovery of pulsars in the late 1960's, it has been assumed that the pulsar at the center of the Crab Nebula is an excellent representative of young neutron stars. However, growing evidence from a variety of observations suggests that the standard picture is fundamentally flawed: the Crab pulsar and others like it may in fact be just one manifestation of a far more diverse young neutron star population than has been appreciated. In this talk, I will describe both the traditional point of view, as well as present the latest evidence, from radio and X-ray observations, for this unexpected diversity in young neutron stars.

DATE:Mar 13
SPEAKER:Nick Bigelow
ORGANIZATION:University of Rochester

Laser Cooled Atomic Mixture Vapors: From Cold Molecules to BEC

Laser cooling has opened the door for a broad class of exciting experiments in atomic physics. To date, this work has emphasized the physics of ultracold atoms of a single atomic species. At Rochester, we have taken this problem in a different direction by creating laser cooled atomic mixture vapors - that it gasses of multiple atomic species cooled and trapped in the same apparatus. In this talk I will describe some of our work on this system. In particular I will describe out work on the photoassociation of the free atoms into bound ground state molecules and on the physics of a multi-component Bose-Einstein condensate.

DATE: Mar 20
SPEAKER:Eric Cornell
ORGANIZATION:JILA

The Low-Temperature Magnifying Glass: Bose-Einstein Condensation and the Visible Machinery of Quantum Mechanics

In a gas of Rubidium atoms cooled within 20 billionths of a degree of absolute zero, we use optical techniques to create, and then follow the propagation of, phase singularities in a superfluid.

DATE:Mar 22
SPEAKER:Donald Terndrup
ORGANIZATION:Ohio State University

Does Metal Abundance Matter in Angular Momentum Evolution?

We have been engaged in new observational and theoretical studies of the angular momentum evolution in young and intermediate-age open clusters. Stars in these clusters frequently arrive on the main sequence with rapid rotation rates, but then lose angular momentum through a magnetized wind. The theory yields expectations about how the loss rate depends on metallicity, which in turn affects the depth of the convection zone and the stellar moment of inertia. We use the "Southern Pleiades" cluster NGC 2516 to test these expectations. If time permits, I will give an update on open cluster distances from main-sequence fitting compared to those from Hipparcos parallaxes.

DATE:Mar 27
SPEAKER: Giles Santyr
ORGANIZATION:Carleton University

Magnetic Resonance Imaging of Hyperpolarized Noble Gases

With the recent development of inexpensive and efficient laser technology it is now possible to create litre quantities of hyperpolarized noble gases (xenon and helium) in as little as a few hours and with polarizations several orders of magnitude larger than that previously possible. This increase in polarization considerably enhances applications of conventional Nuclear Magnetic Resonance (NMR) and Magnetic Resonance Imaging (MRI) by increasing sensitivity, thus allowing detection of very small quantities of these gases and opening up many new possibilities for their use in industry, science and medicine. This presentation will describe the theory, methodology and applications of hyperpolarized noble gases with particularly emphasis on xenon MRI in vivo.

DATE:Apr 3
SPEAKER:Marshall McCall
ORGANIZATION:York University

THE CHEMISTRY OF NAKED GALAXIES

Since stars form out of clouds of gas, one might normally expect to see stars shrouded in gas. However, throughout the universe are found bare collections of stars which contain essentially no gas. These include elliptical galaxies, dwarf spheroidal galaxies, and the bulges of spiral galaxies. Was all the gas used up in forming the stars? Or, did these bodies throw off their gas at an early age? Studies of the chemical composition and motions of the stars tell the tale, and even elucidate how much baryonic matter the systems started with. WARNING: An attempt will be made to create a galaxy in a test tube.

DATE:Apr 3
SPEAKER:Michael Roney
ORGANIZATION:University of Victoria

A Puzzle at the Turn of Century: Why is the Universe Unbalanced?

All evidence currently points to a universe composed of matter particles: protons, neutrons and electrons, rather than their antimatter counterparts: antiprotons, antineutrons and positrons. Yet matter and antimatter should have been produced in equal abundance at the Big Bang. Therein lies one of the outstanding puzzles confronting the physicist at the turn of the 21st century: Why does the universe now consist only of matter? Why is the universe so unbalanced? One of the conditions for such an imbalance is the phenomenon of 'CP violation' and its study will yield key pieces of the puzzle. In this colloquium, we'll examine this phenomenon in the weak interaction and how new experimental tools are probing it. This winter's results from the recently commissioned BaBar Experiment at the Stanford Linear Accelerator Center will be highlighted.

DATE:Apr 10
SPEAKER: Amanda Peet
ORGANIZATION:University of Toronto

String Theory: what it is and what it's good for

String theory is the most promising candidate for a unified theory of the electroweak, strong, and gravitational interactions. It illuminates the physics of ultra-short distances and ultra-high energies. There has been much progress in the field in the last six years taking our understanding beyond perturbation theory. Buzzwords include Dualities, D-Branes, exact computations of the Bekenstein-Hawking entropy, Gravity/Gauge Correspondences, Holography, and most recently Non-Commutative theories. The advent of these and other new concepts, mechanisms and theories has led to new ways of building models of our low-energy world. In my talk I will give a non-technical survey of new ideas, with emphasis on applications to physics of quantum black holes, including resolution of spacetime singularities.

DATE:Apr 17
SPEAKER:Andrei Rakitin
ORGANIZATION:Department of Electrical and Computer Engineering, University of Toronto

Physics of engineered carbon nanotubes and DNA macromolecules: Plenty of physics and little engineering

DATE: Sep 5
SPEAKER:I.C. Percival
ORGANIZATION:Queen Mary and Westfield College, London, U.K

Bell nonlocality and the detection loophole

John Bell showed that there are some ideal experiments on entangled quantum systems for which the resultant correlations cannot be explained on the basis of purely local interactions. Despite many attempts, no published real experiment has demonstrated this Bell nonlocality without the detection loophole. Recent reports suggest that this loophole is about to be closed, thus providing the first experimental confirmation of Bell nonlocality. The talk will present a general analysis of real experiments, which are significantly different from the ideal ones, with the emphasis on the detection loophole.

DATE: Sep 12
SPEAKER:Sampa Bhadra
ORGANIZATION:York University

Looking Deep Inside the Proton

We delve into the simple proton to unearth the interactions of quarks and gluons within. These interactions are viewed with the world's largest electron-proton microscope: the ZEUS detector operating at the HERA accelerator in Germany. The high collision energy provides a small spatial resolution (small wavelength) probe, the virtual photon exchanged between the electron and proton. QCD, the theory of strong interactions that govern the quarks and gluons, is tested to great precision from the results of the quark density distributions in the proton. In addition, the structure of the photon can also be studied in photoproduced events. We will see how the data compare to the current theory that explains what we know of the fundamental particles and forces, namely the Standard Model. The real challenge is to probe for signs of physics that is not so Standard after all!

DATE: Sep 19
SPEAKER:Richard Peltier
ORGANIZATION:University of Toronto

Solar Luminosity, Atmospheric Carbon Dioxide and Global Climate

Planetary climate continues to evolve under the joint constraints provided by both the effective and absolute luminosity of the Sun and of the concentration of radiatively active trace gases in the atmosphere, the most important of which is carbon dioxide. Observational evidence of the detailed nature of this evolution exists from the Neoproterozoic period of Earth history (approximately 600 million years ago) to the present. An important component of this information consists of evidence of global glaciation events. In the most distant past the impact on global climate of continental rearrangements due to the drift process has also been profound. A variety of detailed physical models of climate evolution have been formulated that allow us to confront the observational evidence in such a way as to test physical understanding. I will present the results of analyses based upon such models for both the distant and more recent past as well as for the future.

DATE: Sep 26
SPEAKER:Robert Mann
ORGANIZATION:University of Waterloo

A New Look at the Oldest Problem in Physics

Perhaps the oldest problem in physics is the N-body problem: given some number, N, of bodies and their mutual interactions, what will be their state of motion from a given set of initial conditions? This problem is notoriously difficult when the interaction between the bodies is due to gravity. I will discuss the history of this problem, and why it is so difficult to deal with in Einstein's theory of gravity. I shall then describe a new approach to the problem I have taken recently, and illustrate some new exact solutions that have recently been obtained. I will finish by outlining the prospects this model has for teaching us new things about astrophysics,statistical mechanics and relativity.

DATE: Oct 3
SPEAKER:Dwayne Miller
ORGANIZATION:University of Toronto

Mother nature and the molecular big bang

Biological molecules are extremely complex systems. Even on the single-molecule level, there are typically more than 10,000 degrees of freedom that are strongly coupled to form a highly entangled system. In addition, the molecular structures are marginally stable. Small perturbations from the operating point cause catastrophic collapse of the functionality of the system -- "life on the edge". Despite the complexity and narrow stability regime, these systems are able to take relatively small amounts of energy (e.g., a single bond) and highly direct this energy into functions. How is it possible for such a complex, highly damped system to direct energy so efficiently? This talk will examine this so-called "Levinthal's paradox". The proper description of this phenomenon holds the key to understanding the scaling of biological systems from mesoscopic to macroscopic length scales. New nonlinear spectroscopic methods based on the use of diffractive optics have made it possible to follow protein motions of less than .001 nm with femtosecond time resolution. The picture that is emerging is that collective modes inherent in protein structures play the key role as the "directors" and seed the scaling to longer length/time scales.

DATE: Oct 10
SPEAKER:Bruce D. Gaulin
ORGANIZATION:McMaster University

Exotic Magnetic Ground States

Most magnetic materials enter either ferromagnetic (like fridge magnets) or antiferromagnetic states at low enough temperatures, and their properties are largely well understood. However, the last ten years has seen intense interest in magnetic materials which cannot enter such conventional low temperature states. This can be due to competition between the local geometry of the magnetic ions in the solid, and the nature of their interactions, known as geometrical frustration. It can also be due to effective low dimensionality in the materials, wherein the magnetic atoms are configured in either chains or sheets within the material. These structures can preclude conventional low temperature states, and allow a non-magnetic, singlet state to form. I will discuss examples of such exotic magnetic ground states, and how we have studied their unusual properties using neutron and x-ray scattering techniques.

DATE: Oct 17
SPEAKER:Jean Simon Boulanger
ORGANIZATION:National Research Council Canada

Time Metrology: A Matter of Uncertainty

The SI second, or Time, is defined by the hyperfine transition of the ground state of caesium atom at rest. The most modern clocks (caesium fountains) are achieving accuracy close to 10^-15. This is the most accurate measurement ever made by man. Yet, the metrology community prefers to talk about uncertainty to describe this feat of science and technology rather than to talk about accuracy. The talk will first go briefly through the history of atomic clocks, stressing where uncertainties, or limits, of the various realizations of the definition of the SI second are lying. National Research Council of Canada played a great role in the development of better classical atomic beam clocks by taking radically different approach to the problems. In the 80's, NRC has broken some uncertainty limits previously seen as the ultimate ones, reducing the total uncertainty to 10^-14. A second part of the talk will focus on the most modern realization of the SI second: the caesium fountain. A decade ago, a new science emerged: atom cooling by lasers. Not only pairs of laser beams at the right wavelength can cool atoms, but also a cleaver modulation of individual beams can accelerate a cloud of cold atoms in any direction. A forty-year-old dream, the Zacharias's fountain, could become a reality. A French team was the first one to succeed and immediately, the absolute uncertainty of the realization of the SI second was reduced by nearly an order of magnitude. Many other national laboratories, including NRC, are now building caesium fountains. At NRC, we are developing our fountain along original thoughts, still aiming at refining measurements and pushing the limits of uncertainties as far as possible, sometimes breaking again some taboos. The last part of the talk will look at the future of time and frequency measurements. Caesium fountains, Rubidium fountains, single ion traps, clocks in space, pulsars? Actual technological limits may well forbid us to predict which one will be the most accurate or useful. Time metrology is still condemned to live in a world of uncertainty for a while, probably forever.

DATE: Oct 24
SPEAKER:Barth Netterfield
ORGANIZATION:University of Toronto

Cosmic Microwave Background

Since the discovery of the Cosmic Microwave Background (CMB) in the 1960's, it has been recognized that measurements of spatial structure in the CMB would significantly increase our understanding of the Universe. Images of acoustic oscillations in the primordial plasma are frozen in at recombination, when the ionized plasma cools to a neutral gas. The angular spectra of these fluctuations can be used to limit the value of cosmological parameters, such as the total energy density of the Universe, and the physical density in Baryons. BOOMERANG, a Long Duration Balloon Borne telescope, which made its first antarctic flight in Dec 1998 - Jan 1999 has produced images of the CMB with sensitivity and resolution adequate to resolve these fluctuations, and to capitalize on the CMB's cosmological potential. These images, and their associated angular power spectra will be presented, along with cosmological implications.

DATE:Oct 31
SPEAKER:Paul Corkum
ORGANIZATION:National Research Council Canda

Molecular Optics

Molecular optics shares with atomic optics the aim of controlling all aspects of motion: position, velocity and acceleration. It also aims to control intrinsically molecular properties such as alignment, orientation, rotation and angular acceleration. We use intense non-resonant laser light to control both molecular motion and alignment. Strong fields exerts very large forces on the molecule - proportional to the gradient of the Stark shift. We use this force to deflect I2 and CS2 molecules. We trace the direction of molecules in a molecular beam, showing that the molecules pass near the center of a 1.06 mm or 10.6 mm laser beam will focus. It also can apply an extremely strong torque on an anisotropic molecule. We use the torque to align or accelerate CS2 and Cl2. We spin CL2 from rest to a rotational energy sufficient to break it by the centrifugal force in just 40 ps.

DATE:Nov 7
SPEAKER:James Alcock
ORGANIZATION:York University

Experience, uncertainty and the psychology of belief

Scientists take pride in personal rationality, and yet over the years, some scientists - including some very notable physicists - have championed belief in paranormal and supernatural phenomena that, if real, clearly violate the "laws of physics." I argue that this comes about because human information processing occurs on two levels, the rational/intellectual and the experiential/emotional. Both processes are critically important for individual survival. However, the products of experiential processing sometimes are incompatible with rational analysis of the same experiential data, leaving an individual torn between personal experience and rational/scientific belief. Some people can live with the uncertainty that this produces, while others cannot, and instead modify their beliefs to accommodate their experience.

DATE: Nov 14
SPEAKER:Donna Strickland
ORGANIZATION:University of Waterloo

Progress Towards Chirped Pulse Dissociation of Molecules

Two different techniques of climbing a vibrational ladder of a simple diatomic molecule will be explored in our laboratory. The first will use a temporally chirped, high intensity, mid-infrared pulse. The second technique uses two synchronous, oppositely chirped pulses. The two pulses will interact with the vibrational modes of the molecule by a Raman process. In both cases, the optical pulses are chirped so that as a vibrational level is populated, the laser frequency is changed to be resonant with the next higher vibrational state but not with the lower. Our lab is ideally suited to carry out these investigations since we have developed an amplified, dual-wavelength, femtosecond laser system. We are currently developing a mid-infrared system based on difference frequency mixing the two outputs.

DATE:Nov 21
SPEAKER:John Landstreet
ORGANIZATION:University of Western Ontario

THE PUZZLING STARS OF THE MIDDLE MAIN SEQUENCE

The stars in the middle of the main sequence are stars rather similar in internal structure to our own sun, but are substantially less well understood. They present a large number of very specific puzzles, some connected with their development and some related to specific physical processes that occur inside them. For example, most of these stars have relative abundances of various chemical elements in their atmospheres that differ from the relative abundances found in other stars of the same age, and some have exceedingly peculiar chemistry. Some (but not most) of these stars have coherent magnetic fields of strengths that sometimes exceed 1 Tesla. Some rotate within a factor of two of breakup velocity, while other have 0.0001 times lower angular momentum. And some reveal (through the shapes of their spectral lines) atmospheres almost free of convective motions, while others have some of the largest convective velocities found in any stars. This talk will discuss our current understanding of some of the interesting astrophysical puzzles presented by these objects.

DATE: Nov 23
SPEAKER:Undergraduate Student Talks
ORGANIZATION:York University

STUDENT PRESENTATIONS AT CUPC 2000, QUEBEC CITY

Itay Yavin
Coherent excitation of a regular array of molecules
We calculate the energy eigenvalues and eigenfunctions of systems of N identical molecules, in regular geometric arrangements. The molecules interact via the long-range dipole-dipole interaction; hence, we do not limit ourselves to nearest-neighbor interactions, but rather include the interaction between all pairs in the array. We consider two cases:1. (Coherent) single-molecule excitations of a variety of 2- and 3-dimensional arrays: a single exciton/polariton; and 2. the double excitation of a circular ring of molecules: a biexciton/bipolariton. We obtain analytical solutions for the energies and eigenstates by matrix diagonalization, exploiting the regular symmetries of our arrays. With these eigenstates, we can calculate the absorption and emission properties of there systems. We hope to apply these calculations to the study of the spectroscopy of biological molecules, and to calculations involving the quantum entanglement of pairs of atoms.


Yasaman Soudagar
Metal Dimers and Approximations to Schrodinger Equation
We solved approximate Schrodinger equations (variants of density functional theory) for AB dimers, where A, B = Li, Na, K, Ni, Cu, Ag. We compared the calculated bond energies, and bond lengths to experimental data to find the best approximation methods, and used these methods to make predictions about the experimentally unknown AB dimers. These new data are necessary to model metal alloys.


Andrew Vorozcovs, M. Weel, G. Spirou, T. Mikaelian, A, Andreyuk, and A. Kumarakrishnan
High-precision shutter control of a CCD camera for imaging clouds of ultra-cold atoms
Imaging the expansion of a cloud of cold, trapped atoms after turning off confining forces requires a device capable of taking pictures on a suitably fast time scale with adequate shutter timing resolution. A method of constructing such a device using an inexpensive commercially available CCD camera is presented. The device is shown to be capable of obtaining sequences of frames with delays between the individual frames of the order of 1/10,000 second. The method of recording such measurements is visually illustrated by photographing the path of an electron beam across the screen of an oscilloscope. The ultimate goal of this project is to perform measurements of the expansion of cold atom clouds over periods of the order of 20 ms.


Tsoline Mikaelian. M. Weel,. G. Spirou, A. Vorozcovs, A. Andreyuk, and A. Kumarakrishnan
Numerical Simulations of a Simplified Ioffe Trap for Realizing Bose-Einstein Condensation
We present numerical simulations of the magnetic field due to a simplified Ioffe-Pritchard trap that has recently been used to obtain Bose-Einstein condensation using Laser cooling techniques. This trap converts a quadrupole field into an Ioffe configuration by means of a conical solenoid, placed orthogonally to the axis of symmetry of a pair of quadrupole coils. In particular, we describe the details of 1-D and 2-D simulations used to calculate the magnetic field for this arrangement and point out the advantages of this configuration of magnetic field coils. We compare the results with the magnetic field obtained when the conical solenoid is replaced by a finite cylindrical solenoid. We also examine the re-scaling of the coil parameters to accommodate larger diameter trapping beams. Finally, we consider how an experiment based on these simulations can be realized.


Gloria Spirou, T. Mikaelian, M. Weel, A. Vorozcovs, A. Andreyuk, A. Kumarakrishnan (York University), P. R. Battle, R.C. Swanson (AdvR Inc.)
A high speed modulated retroreflector for Lasers
We have used an acousto-optic modulator (AOM) to impose an amplitude modulation on an incident Laser beam. The amplitude modulated beam can be sent back through the AOM so that it returns along the direction of the incident beam. However, the return beam is frequency shifted with respect to the incident beam. This feature allows us to detect the amplitude modulated signal with high signal to noise using heterodyne detection. Since the setup is very simple and compact, it may be ideally suited for certain forms of high-speed optical communication.


Monica Kelemen
Probing The Heart of a Dying Star (VLBI Observations of SN1993J)
Massive stars throughout our universe end their lives through cataclysmic explosions called supernovae. While the chances of seeing one of these events in our stellar neighbourhood are quite slim, they are easily detectable over intergalactic distances. All supernovae emit vast amounts of optical radiation but a fraction of them are also accompanied by strong radio emissions. The technique of Very Long Baseline allows us to observe the remnants of recent supernovae in very high detail in the radio part of the electromagnetic spectrum. Through periodic observations of these celestial objects we are able to watch them change as they expand and eventually join the interstellar medium of their parent galaxies.


Ian Harnarine
The Straw That Broke the Quark's Back Experimental Particle Physics is an investigation into the fundamental nature of matter. At the HERA accelerator in Hamburg, Germany, beams of high energy electrons and protons are made to collide. Analysis of the products of these collisions allows for greater insight into the interactions of the quarks which compose the proton. York University is currently involved in the construction of a type of detector, the Straw-Tube Tracker, which will be used to reconstruct the paths of high energy charged particles created in electron-proton collisions. I will discuss the construction and the components of the Straw-Tube Tracker as well as how it works. I will also talk about what new information will be gained from the use of the Straw-Tube Tracker


Julie Tome
Observing the Proper Motion of the Gravity Probe B Guide Star Using VLBI
In 2002, the Gravity Probe B (GP-B) satellite will be launched. Its mission is to verify two predictions of Einstein's general theory of relativity. General relativity predicts small changes in the direction of the spin axis of gyroscopes in polar orbit, which the mission will measure. To achieve this, a reference point is needed. Very precise measurements of the proper motion of the guide star HR8703 are needed to accurately measure these subtle changes. In this talk, I will give an introduction to the GP-B missions and discuss the tracking of Hr8703 using very long baseline interferometry (VLBI).


Matthew Weel, G. Spirou, A. Vorozcovs, T. Mikaelian, A. Andreyuk, and A. Kumarakrishnan
Locking Lasers to trap atoms
We have used a lock-in amplifier and a saturated absorption spectrometer to lock a Laser to the center of a Rubidium resonance line. The locking scheme gives us precise control of the Laser frequency which is essential for trapping atoms in a magneto optical trap. We describe how the scheme works, as well as our progress toward trapping atoms.

DATE:Nov 28
SPEAKER:Allan Griffin
ORGANIZATION:University of Toronto

BEC: THE COLLECTIVE DYNAMICS OF A SUPERFLUID BOSE GAS

The discovery in 1995 of Bose-Einstein condensation (BEC) in trapped laser-cooled atomic gases has opened up an exciting field of research on a new superfluid phase of matter. Recent experimental advances allow one to study the collective dynamics of these Bose-condensed gases in the collisionless as well as in the collision-dominated (or hydrodynamic) region. This colloquium will review recent theoretical work, with emphasis on the two-fluid hydrodynamics of these gases, with analogies to similiar behaviour found in superfluid Helium.

DATE:Dec5
SPEAKER:Stephan Leonard
ORGANIZATION:University of Toronto

Photonic crystals: controlling and trapping light at the micron scale

Photonic crystals are a new class of periodic dielectric structures, capable of inhibiting the propagation and emission of light. Within a spectral region known as a photonic band gap, no propagating modes exist inside a photonic crystal. This remarkable feature opens the door to a new arena of physics and applications, both at the classical and quantum level. Although photonic crystals were proposed over a decade ago, the field has experienced rapid growth in the past two years due to advances in fabrication techniques. Recently, three-dimensional photonic crystals, composed of a face-centered cubic lattice of air spheres in silicon, were fabricated at the University of Toronto. These crystals are expected to possess a complete photonic band gap in the near-infrared, near the telecommunications wavelength of 1.5 microns. In this talk, following a brief introduction to the field of photonic crystals, this recent work will be presented. I will also discuss some results from optical experiments involving two-dimensional silicon photonic crystals. In particular, I will describe how photonic crystals can be made tunable via the incorporation of liquid crystals and how a new type of optical waveguide, which does not employ total internal reflection, can be created using photonic crystals.

Departmental Seminars Winter 2000: Abstracts

Recent Developments in Spatial Imaging

I will be speaking on recent developments in spatial imaging and a new system for synthesizing computer generated holograms under development by our research team. In particular the presentation will include:

• New advances in the evolution of the holographic stereogram
• A practical demonstration of the origination of a computer generated hologram
• Examples of computer generated artworks and large format holograms

The Electromagnetic Trap - At the Limits of Measurements in Physics

Electromagnetic traps confine charged particles to very small spaces using electromagnetic fields that are minuscule compared to the fields in the vicinity of the particles themselves. They therefore provide extremely clean and gentle confinement. Using such traps, single ions have been confined to within microns and cooled so as to spend 80% of their time in the quantum ground state of their simple harmonic oscillation. The possibilities offered by such confinement were first demonstrated in the Nobel prize winning work of Dehmelt at Washington State University in which the g-factor of the electron was measured to an accuracy 400 times that of any previous measurement. A remarkable feature of such traps is that they can be used on a single particle for up to months at a time. In fact, for the highest accuracy measurements it is essential that there be only one particle in the trap at once. Recent developments in deceleration and cooling techniques have allowed such traps to be used on exotic particles that can only be produced on Earth by extremely high-energy particle interactions. These particles are not only of interest in nuclear physics but also in astrophysics since they are thought to play an important role in stellar explosions. In ideal cases, mass accuracies of up to 1 part in 10¹³ can be expected. The techniques involved have also recently become of interest in biomedical research because of the possibility of detecting and identifying single molecules. This talk will introduce the general aspects of electromagnetic trapping and the particle deceleration, capture and identification techniques involved in their use. It will also present recent results in various laboratories that have implemented these techniques and introduce some of the projects planned for the immediate future.

Studying Unconventional Superconductors with Muons

In 13 years or so since the discovery of high temperature superconductivity there has been an intense level of research in all areas of superconductivity. During this same time period, the technique of muon spin relaxation/rotation has emerged as an extremely powerful tool for the study of all types of condensed matter systems, especially superconductors. In this talk I will introduce uSR and describe some of our recent results on several exotic superconducting systems including high-Tc cuprates, Sr₂RuO₄, and heavy fermion materials.

Photometric Detection of Extra-Solar Planets

The centuries old question about the existence of planets around other stars has recently been answered loudly in the affirmative. The Galaxy has lots of them! However, the ones which have been found first are, not surprisingly, the ones which are the easiest to find - large planets (many bigger than Jupiter) orbiting their stars at distances only 1% of the Jupiter-Sun distance. Such planets produce relatively large wobbles in the parent stars, with correspondingly large Doppler shifts, enabling the spectroscopic discoveries of the companions. There have not yet been any extra-solar discoveries of the other type of major planet that we know about in the Solar System - the terrestrial ones. Major national and international space agencies are now planning future missions to address the question of extra-Solar Earths. The plans include very large and expensive interferometric experiments that will actually obtain spectra and resolved ../images of such planets. But there is a major assumption underlying these missions - the very existence of the class of target for which the missions are designed. The concerns are justified - there are good theoretical reasons to fear that Earths could not coexist with the hot Jupiters mentioned above. To address the possibility that there may be nothing for the Earth-finders to find, a precursor NASA mission to verify their existence is being developed at the NASA Ames Research Center. It known as Kepler. It will survey about 100,000 stars from space, to look for evidence of planetary transits. The challenges are formidable, but they appear to be manageable. This talk will discuss the state of the Kepler mission, and also some of the scientific considerations of the new discipline known as astrobiology, which studies questions about habitable extra-solar environments.

Sand Waves: the curious dynamics of segregation patterns

Unlike fluids, dry granular materials often stubbornly refuse to mix when shaken or stirred. Instead, they sort themselves by size or shape. These "segregation" effects are common in many industrial processes involving grains from cake mixes to gunpowder. I will describe experiments on segregation along the axis of a partially filled, horizontal rotating tube -- a so-called "drum mixer", which actually unmixes. I will attempt a live demonstration of this phenomenon. Naive theory suggested that segregation was the irreversible result of a kind of negative diffusion analogous to spinodal decomposition. We experimentally discovered a much richer segregation dynamics that involves travelling structures. These effects have been captured by a recent model.

Atom Trap Studies of Electron-Neutrino Correlations in Beta Decay: Search for Scalars

Lasers can be used to cool and trap neutral atoms. We use a magneto-optical trap to capture beta decaying nuclei. The neutrino momentum can be reconstructed by detecting the low energy nuclear recoils in coincidence with the beta particle. The angular distribution of the neutrinos is predicted by the Standard Model, and deviations from that prediction are sensitive to new interactions. The trapping is described along with other techniques to polarize nuclei to test whether parity is maximally violated in the charged weak interaction. Preliminary measurements of the beta neutrino angular distribution from a spin 0 nucleus will be presented. Our goal is to set limits on the existence of new scalar bosons complementary to those set by high energy colliders.

Solution to the Bethe Logarithm Problem in Helium and High Precision Comparisons with Experiment

There now exist many measurements of transition frequencies in atomic helium accurate to a few MHz. A comparison with theory brings to the fore one of the most difficult challenges in atomic physics - the calculation of QED shifts in systems more complicated than hydrogen. The principal difficulty comes from th so-called Bethe logarithm term arising from the electron self-energy. To this day, the lack of accurate two-electron Bethe logarithms for the various states of helium remains a major obstacle to further progress in the comparison of high precision theory and experiment. To adddress this problem, we have developed a remarkable new variational technique which is capable of representing distance (and energy) scales over many orders of magnitude. The fractal-like nature of the problem will be discussed, and comparisons with high precision measurements for transition frequencies in helium will be reviewed.

Outflows and the Disk-Halo Connection in Galaxies

While nuclear jets from extra-galactic radio sources have been known and studied for many years, the discovery that nearby spiral galaxies may also experience outflows is comparatively recent. The more spectacular outflows originate from the nuclear regions, usually in energetic starbursts. However, there is mountiing evidence that many, perhaps all star forming galaxies may also experience outflows from their disks. These outflows are inferred from kpc-scale HI supershells, ionized gas filaments, X-ray emission, and radio continuum extensions which bridge the disk-halo region. Significant flows are implied, which must be taken into account at least in models of the chemical and star forming history of the galaxy and, possibly, the enrichment of the IGM as well. This talk will summarize the observational evidence for such outflows and outline some of the current questions and challenges in this field of study. Some recent results from the GMRT will also be presented.

In Search of Lost Time

Radiometric dating was invented at McGill University by Ernest Rutherford in 1904. His invention revolutionized our view of the age of the earth and the age of humans. I will review this dramatic change of view, and describe how measurements made with the aid of nuclear reactors, lasers and mass spectrometers have been casting new light on the timescale of human evolution. The evidence is now that our hominid ancestors split off from the Australopithecine line in the Ethiopian rift valley somewhere in the time interval stretching from about 2.9 to 2.3 million years ago. Thus "our" brains expanded by about a factor of three or four in roughly 2.5 million years. I will also describe how the recently discovered feathered dinosaurs were dated in Toronto before they were discovered.

Think small, get the big picture: physics at the attometer scale

Ever since Rutherford, scattering has been a widely used and successful particle physics method to investigate the structure of matter. The accelerator HERA, located in Hamburg, Germany, and in operation since 1992, can probe the proton structure down to 10^-18 meter, one thousandth of its size. Collisions of point-like electrons or positrons on protons yield a lot of information on the composition of the proton in terms of quarks and gluons, test the interaction processes and challenge our understanding on a wide kinematical scale. A brief review of the experimental phenomena will be presented, followed by details of specific examples where, in the «real» world of the laboratory, scattered quarks and gluons may be observed as jets of particles in the ZEUS detector. The question "Is there a sub-structure to the quark?" will also be addressed.

PINPOINTING SUPERNOVAE WITH NEUTRINO TELESCOPES

When a supernova occurs 99% of the energy released is carried away by a burst of neutrinos distributed over only a few seconds. Like a spherical wave this intense flux of neutrinos sweeps through the universe practically unimpeded. As it passes through the earth a few neutrinos will interact with terrestrial neutrino detectors such as those neutrinos observed, for SN1987A, in the Kamioka and IMB detectors. The present generation of neutrino detectors, including Canada's Sudbury Neutrino Observatory, will see, for a galactic supernova, many more neutrinos than the dozen or so seen in 1987. This opens up the possibility of using the new "neutrino telescopes" to instantly detect, and locate on the celestial sphere, a supernova as it occurs. Hopefully this early warning will give the astronomical community the chance to observe the initial development of the supernova. The talk will describe the motivation, mechanics, and capabilities of the newly formed Supernova Early Alert Network.

Measurements across the Optical Spectrum with Atomic Clock Accuracies

The unique environment of a single trapped atomic particle, laser cooled to near rest provides one of the nearest man-made approximations to a true isolated quantum system. We have developed a new type of optical frequency standard based on referencing an ultrastable laser to a narrow reference transition in a single ion of strontium. After many years of effort, a frequency bridge between the ion transition frequency and the Cs atomic clock realisation of the SI second was created such that the ion frequency is now known to a relative accuracy of 5 X 10^-13. The transition is now one of the best known in the optical spectrum and has estimated systematic shifts which are at the 10^-15 level or below. We have applied this powerful new reference to a series of precision determinations of other key absolute optical frequencies. A summary of the recent results obtained will be presented together with an overview of recent world-wide advances for providing the "missing link" in creating optical frequency atomic clocks.

Experimental Study of Quantum Chaos with Ultra-Cold Atoms

In this talk I will review experiments at the interface between nonlinear dynamics and quantum mechanics, a field known as quantum chaos. We study the motion of ultra-cold atoms in nonlinear optical potentials in a regime of classical chaos. We observe in this system an initial momentum growth following classical predictions, followed by a quantum suppression of diffusion. Recent work in my group has focused on the role of decoherence in recovering the classical limit. I will discuss these new results and outline some future directions for research at the quantum/classical border.

Molecular Optics

Molecular optics shares with atomic optics the aim of controlling all aspects of motion: position, velocity and acceleration. It also aims to control intrinsically molecular properties such as alignment, orientation, rotation and angular acceleration. We use intense non-resonant laser light to control both molecular motion and alignment. Strong fields exerts very large forces on the molecule - proportional to the gradient of the Stark shift. We use this force to deflect I₂ and CS₂ molecules. We trace the direction of molecules in a molecular beam, showing that the molecules pass near the center of a 1.06 mm or 10.6 mm laser beam will focus. It also can apply an extremely strong torque on an anisotropic molecule. We use the torque to align or accelerate CS₂ and Cl₂. We spin CL₂ from rest to a rotational energy sufficient to break it by the centrifugal force in just 40 ps.

Instabilities in Thin Polymer Films: From Pattern Formation to Rupture

Thermal fluctuations of the surfaces of thin polymer films can be amplified by the long-range, attractive van der Waals or dispersion force which acts across the film. When freely-standing polymer films are heated, this instability leads to the formation of holes. We have measured the formation and growth of holes in very thin, freely-standing polystyrene (PS) films to learn about the mobility of the confined polymer molecules. We have also symmetrically capped freely-standing PS films with thin, solid layers to probe the effects of mechanical confinement. Aggressive annealing of the trilayer films produces a novel in-plane morphology. This morphology, which has potential technological applications, can be understood in terms of the balance between the decrease in free energy associated with the dispersion interaction and the increase in free energy associated with the bending of the capping layers. The general nature of the morphology, and its reversibility, will be demonstrated.

Numerical Simulation of Cosmic Structure

Studies of cosmic structure are entering a period of substantial improvement in sophistication and accuracy. A wealth of observational data is becoming available, ranging from studies of galaxies, clusters and their cosmic distribution, to the high redshift universe and observations of microwave background fluctuations. Numerical simulations are the crucial theoretical probe of the non-linear gravitational and hydrodynamic cosmic structure that we observe. The large range of scales encountered, at least ten thousand in length, and density contrasts of up to a million, make the simulation of cosmic structure a formidable challenge to computational physics. The talk will discuss the techniques that have been developed to address this problem, and show how highly efficient cosmic hydrodynamic algorithms when coupled with current supercomputers are producing results of unprecedented scope and resolution. Results will be presented of billion-particle large-scale structure simulations, of high resolution galaxy formation studies and of simulations of the first cosmic objects to form at high redshift.

Departmental Seminars Fall 1999: Abstracts

Asteroids From Another Solar System

Several stars are now known to have planetary systems. By extrapolation it has been claimed that 4% of all main sequence stars possess such systems. Asteroids are thought to be a byproduct of solar system formation and early evolution, and thus it is a fair assumption that the other planetary systems also have their own asteroid populations. In this presentation I will discuss the mechanisms by which planetary systems of different stars may exchange asteroids between them. The probability of a collision by an asteroid from another system with the Earth is calculated. Finally, we discuss the probability that life on Earth arrived from another planet around another star to the Earth on board an asteroid. The possibility that the life in many planetary systems can have a common origin cannot be excluded.

The Sudbury Neutrino Observatory

The Solar Neutrino Problem is the observation that the experimental measurement of the electron type neutrino flux from the sun is in the range of 0.3 to 0.6 of that predicted by theoretical solar models. A possible explanation for this deficit is that the electron neutrinos produced in the sun undergo flavour oscillation to either muon neutrinos or tau neutrinos and as a result are undetected by the current generation of solar neutrino experiments that are mostly sensitive to electron neutrinos. The Sudbury Neutrino Observatory (SNO) is a heavy water Cherenkov detector designed to measure the neutrino flux from the nuclear fusion reactions in the sun. Located 2 km below ground level in INCO's Creighton mine near Sudbury, SNO consists of 1000 tonnes of heavy water, on loan from Atomic Energy of Canada Limited, contained within a 12m diameter acrylic vessel and viewed by 9600 photomuliplers. Having recently come online, SNO is sensitive to muon and xtau neutrinos in addition to electron neutrinos and will thus be able to measure the total flux of all neutrino flavours from the sun. If neutrinos other than electron neutrinos are detected in SNO, it will be an unambiguous signature of neutrino oscillations. The physics, calibration and present status of the experiment will be presented.

Quantum Information: What the Heck's All the Fuss For?

I will try and explain why many physicists around the world are delving into areas of mathematics, computer science and cryptography, that until a few years ago would have given them cold shakes. I'll start by talking about a simple game that can only be won 100% of the time by Team Quantum, who have the ability to share quantum information. From there I'll continue to boldly skirt the issue of what quantum information really is, while trying to expose you to some of its weird and wonderful properties in some very simple systems. Finally I'll discuss some ongoing work at the University of Toronto which is aimed towards using photonic band-gap materials for quantum information processing.

b Quarks, B Factories and New Physics

This summer two "B factories", facilities that will produce bottom (b) quarks by the tens of millions, came on-line in the U.S. and Japan. These will be followed in the next several years by a number of additional dedicated experiments that will provide the opportunity to study the interactions of b-quarks in unprecedented detail. In this talk I will discuss some of the physics that these "low energy" high energy physics experiments will probe, including why the universe is in a superconducting ground state and (with luck) the origin of the matter-antimatter asymmetry in the universe.

The Solar Neutrino Problem and Astrophysical S Factor

One of the outstanding problems in physics today is with the observed number of solar neutrinos - significantly fewer are observed than predicted. The the high energy neutrinos to which some neutrino detectors, including SNO, are sensitive are produced by the decay of Boron 8 in the sun. In this talk I discuss the solar neutrino problem with emphasis on the astrophysical S factor for Boron 8 production. The previously unexplained low energy behvaiour of the S factor will be clarified and the uncertainties it introduces in the predicted number of neutrinos discussed. The solar neutrino problem can NOT be solved by this bit of nuclear physics.

What Have We Already Learned from the Cosmic Microwave Background?

The COBE satellite, and the DMR experiment in particular, was extraordinarily successful. However, the DMR results were announced about 7 years ago, during which time a great deal more has been learned about anisotropies in the Cosmic Microwave Background (CMB). The CMB experiments currently being designed and built, including long-duration balloons, interferometers, and two space missions, promise to address several fundamental cosmological issues. I will present an evaluation of what we already know, what we are beginning to learn now, and what the future may bring.

For more background you can read the review paper at http://xxx.lanl.gov/abs/astro-ph/9810446.

Recent Developments in Observational Cosmology

I will present a review of the most important developments in observational cosmology during the past year. In particular, I will discuss the results of the Hubble Space Telescope Key Project on the Extragalactic Distance Scale that has reported a value for the Hubble Constant to an accuracy of 10% using observations of Cepheid variable stars in relatively nearby galaxies. The surprising results from two groups using high-redshift supernovae (Type Ia) to measure cosmic deceleration and the global geometry of the universe will also be described in some detail. Current findings strongly suggest that a small but non-zero cosmological constant dominates matter, leading to a positive acceleration in the expansion of the universe.

Looking for New Physics with Charm Quarks

The discovery of the charm quark twenty five years ago played a pivotal role in establishing the electroweak theory of Glashow, Weinberg, and Salam (part of the so called Standard Model of particle physics). Today large samples of charm quark decays are being studied to search for violations of fundamental symmetries in physics, and to look for new interactions beyond the Standard Model. I will discuss results from a recent experiment performed at the Fermilab Tevatron, in which charm quarks were produced by an intense, energetic photon beam striking a metal target.

Research & Career Opportunities in Photonics

Photonics refers to the generation and manipulation of light. The global photonics market is expanding rapidly and is projected to exceed $250 billion next year. This talk gives examples of photonics including nanodevices, optical fibers, ultrafast lasers, biomedical applications, laser cooling and environmental monitoring. Research and career opportunities through the Canadian Institute for Photonic Innovations, which involves 40 private sector companies, 12 government laboratories and 20 universities, are presented. A fun experience with absolutely no equations is promised!

The Undergraduate Lectures

It's not lectures for undergraduates, it's lectures by undergraduates! Four York undergraduates - Jeff Cadieux, Houman Khosravani, Andrew Johnston, and Yasaman Soudagar - represented the department at the 1999 Canadian Undergraduate Physics Conference which took place at the University of Alberta in late October. They each gave a 15 minute talk (two won honourable mention) which they will repeat for our listening enjoyment. Please come and show your appreciation for their efforts. The talks are:

• "VLBI Observations of IM PEG in Support of NASA's GRAVITY PROBE B" by Jeff Cadieux
  In 2001, NASA will launch a billion-dollar satellite called Gravity Probe B. The probe is designed to test two still unproven aspects of Einstein's General Theory of Relativity, and York University has a part in the project. Using an array of radio telescopes located around the world, and a technique called VLBI (Very Long Baseline Interferometry), we examine the star IM PEG, as well as background quasars, over several epochs. The results show several different contour structures and emission strengths for the star. We also observe what appears to be movement of the star's radio-core, on a milli-arcsecond level, over hourly time scales. My talk will present and discuss the results from the four most recent epochs.
• "A Nonlinear Halt to Seizures" by Houman Khosravani
  Over the past decade, techniques from the field of nonlinear dynamics ("chaos theory") have been used for the characterization of seizures in the context of human epilepsy. These methods offer a unique perspective with a powerful edge when it comes to the understanding of complex systems based on global properties. By unraveling 'macroscopic' dynamical behaviour of a system based on its sensitive parameters, one can in principle generate perturbations that alter modes of behaviour in a desirable fashion. Here, such an approach is taken towards epileptic seizures with the aim of characterization as a means for their control. Results of this methodology as applied to these storms of the brain is presented.
• "George's Space: A Non-Mathematical Look at Curved Space" by Andrew Johnston
  Einstein's theory of General Relativity is a beautiful expanation of gravitation, but the daunting mathematics often makes it intimidating for students to try to understand it. The goal of this talk is to give a conceptual understanding of curved space, with no math!
• "From Big Bang to B Factory" by Yasaman Soudagar
  Scientists believe that when the universe was born, the same amounts of matter and antimatter were produced. So, why is there so much more matter than antimatter in our present day world? A physical phenomena known as CP violation is a possible answer to this question. Further investigation of CP violation requires building a new kind of particle accelerator known as a 'B Factory'. In this talk I will clarify the meaning of CP Violation and will discuss how it can explain the excess of matter over antimatter, and why we need B Factories to be able to study this phenomena. 

Departmental Seminars Winter 1999: Abstracts

Cool stuff with STM - Imaging Single Atoms and Molecules on Metal Surfaces by Means of a Scanning Tunnelling Microscope at Low Temperatures

Using a home-built scanning tunnelling microscope operating at 4^o Kelvin provides high stability, excellent vacuum conditions and the ability to image molecules, which would otherwise not adsorb or would diffuse too fast over the surface. The Eigler-type STM, as built in the department of surface science at the Fritz-Haber-Institute in Berlin, was able to determine the adsorption site of single atoms and molecules on low-corrugated metal surfaces directly. In the case of carbon monoxide on the {110} surface of copper, however, image processing was necessary to get proper atomic resolution. Based on Fourier transformation a special filter technique was used to suppress noise. Besides applying a filter, care had to be taken in regard to the imaging method. Benzene on Ni{110}, as a further example, showed an internal structure which could not be related to the atomic structure of the molecule - the symmetry of the molecule still allowed determination of the adsorption site. For the weaker bound benzene on the equivalent copper surface, a special imaging technique was used to permit imaging of the undisturbed molecule and the lattice in a single frame. The adsorption behaviour of molecular oxygen on Cu{110} at 4^o K was examined. At these low temperatures oxygen was found to adsorb both molecularly and dissociatively. The "hot" oxygen atoms showed a very limited mobility on the surface. A precursor state led to cluster formation and anisotropic step decoration with, the molecules mobile only along the <110> direction. Imaging special surfaces such as Cu{111} and Be{10-10} demonstrated the quantum mechanical nature of STM. Free and quasi-free electrons interfered with the adsorbates and step edges to form standing waves. The Fermi surface could then be determined by simple application of a Fourier transformation to the images.

Emulsions, Foams, Crystals, and Glasses: The Physics of Ice Cream

Ice cream is a complex food colloid consisting of fat droplets, air bubbles and ice crystals, all dispersed in a freeze-concentrated, unfrozen aqueous phase of dissolved sugars, proteins, and hydrocolloids. The unfrozen phase is capable of undergoing a glass transition at high viscosity (high concentration and low temperature). Such a structure, with three discrete phases and a large amount of interfacial area, is far from equilibrium and thermodynamically unstable, yet is highly desirable as it leads to a better perceived texture and higher quality. The structural elements of ice cream will be depicted through images from various electron microscopy techniques, and challenges in creating and maintaining its structure during handling will be discussed.

Positron Scattering from Atoms

The existence of positrons was predicted on theoretical considerations by Dirac in the 30's. The interactions of positrons with matter differs from that of electrons and interest in their properties ranges from astrophysics to medical physics. Over the past two decades low energy positron beams have been developed and improved to enable beam experiments to be carried out. Different theoretical techniques for calculation of the properties of positron interactions have been adapted from similar electron interactions. Positron interactions with atoms and molecules differ from electron interactions because of the absence of the Pauli principle between positron and electron, the formation of positronium by a positron and electron and the possibility of annihilation by a positron and electron. The talk will review theoretical and experimental aspects of positron scattering and illustrate them by some recent work on positron scattering from magnesium and neon.

Weird Things About Strange Particles

Strange particles, and in particular the neutral kaon system, are a wealthy source of weird effects. In 1964 it was discovered that kaons violate Charge-Parity (CP) symmetry. CP violation is believed to be responsible for the dominance of matter over antimatter and a necessary effect for the existence of the universe, yet we have learned very little about it since its initial discovery. More recently, it has been observed by experiments at CERN (the European Laboratory for Particle Physics) and Fermilab that the neutral kaon system also violates time reversal symmetry. All of these weird things about the neutral kaon system and their implications will be reviewed and the latest results from the KTeV experiment at Fermilab will be presented.

"Synthetic Seashells" or Self-Assembly of Curved Mesoporous Silica Shapes

A creative combination of self-assembly and microfabrication may provide the way to future nanotechnology because of its inherent simplicity, high reliability and low cost of production. Recently the biomimetic synthesis of extraordinary curved mesoporous silica shapes, such as rods, discoids, spheres, tubes and hollow helicoids, obtained through the nucleation, growth and polymerization of silicate liquid crystals, brings closer to reality the possibility of creating a seashell in-situ. The ability to control curved shapes portend a variety of applications and new technologies where mesostructure and form determine function. In this lecture I shall focus on the problem of morphogenesis of mesoporous silica shapes and surface patterns. A theoretical basis will be outlined to describe the variety of forms and surface designs that result from the liquid crystal stage, silicification and rigidification of silicate liquid crystals. The main factors that are responsible for shape formation will be described. A few examples of numerical 3-D simulation will be discussed to compare theory with experiment and to project beyond the experimental results. A new language of shapes may also emerge from this kind of research.

CAP Lecture - Nanotechnology: Assembling Matter Atom by Atom with a Scanning Tunneling Microscope

In 1959, Richard Feynman gave a lecture entitled "There's Plenty of Room at the Bottom" (reprinted in Engineering and Science, Feb. 1960, p. 22-36). Feynman suggested a variety of experiments and technologies that might be achieved at very small scales. This is an area that is currently getting a lot of hype. Some recent suggestions sound like science fiction, although we are not yet seeing articles titled "Honey, I Shrunk the Factory". Nevertheless, terrific advances have been and are being made. In this talk, I will introduce some of the scientific and technological challenges at the nanoscale frontier. In particular, I will concentrate on scanning tunneling microscopy (STM), which is one of the techniques that allows us not only to look at individual atoms, but also to manipulate them. This allows us to place single atoms and molecules at selected positions, to build structures atom by atom. STM has thus become a critical tool for making and exploring structures on an atomic scale. The lessons these experiments teach us extend beyond the new physics in small dimensions to encompass the general process of learning from biology and chemistry. By then going beyond what is observed in the natural world to deliberate engineering on an atomic scale, we are, indeed, beginning to move into the Room at the Bottom.

Subjective Probability and Bayesian Statistics: Meaning and Applications in Physics

Subjective probability is based on the natural idea that probability is a `degree of belief' which should describe our uncertainty, not just the outcomes of repeated experiments. Bayes' theorem is the logical tool to update the probability in the light of new pieces of information. It will be shown that the so-called Bayesian approach is very close to the intuitive reasoning of experienced physicists, and it allows all kinds of uncertainties to be handled in a consistent way.

Physics with Cold Trapped Ions

Ion traps and laser cooling are tools widely used in laboratories around the world today. The combination of the techniques has, nevertheless, to a large extent been limited to laboratories with interests in frequency and time standards. Recently, the interest in cold, trapped ions has been renewed due to the prospect of constructing quantum computers based on strings of ultra-cold ions. Besides having initiated a project on this topic in Aarhus, we have for the last few years been studying various aspects of spatially ordered structures of ions laser cooled to a few milli-Kelvin. Recently, we have furthermore started investigations on cooling and spatial localization of indirectly laser cooled atomic and molecular ions through the Coulomb interaction with laser cooled ones. The first results of these "sympathetic cooling" investigations look very promising for using cold, trapped ions in many areas of atomic and molecular physics. Using the work performed in Aarhus as a starting point, I will give an overview of the kind of physics that at present and in the future might be done with cold, trapped ions.

Stellar Cannibalism: From Cataclysmic Variables to Supersoft X-Ray Sources

A relatively new class of astronomical objects known as Supersoft X-Ray Sources has been identified using ROSAT satellite observations. Most SSXS's are very luminous and exhibit blackbody spectra with effective temperatures in excess of 10⁵ K. I will show that these observations can be successfully explained if SSXS's are close binaries wherein a white dwarf is cannibalizing its (subgiant) companion and the accreted matter is undergoing thermonuclear burning on the surface of the white dwarf. I will also examine the conditions necessary for stable burning and investigate (using Monte Carlo simulations) the various evolutionary pathways that can ultimately produce these systems. Finally, I will show that SSXS's may be the long sought after "missing link" explaining the progenitors of Type Ia supernovae.

Our Evolving View of Star Formation

Now regarded as an outstanding challenge in theoretical astrophysics, star formation has been an active field of study for only the last several decades. During this time, observational and theoretical advances have led to a continually evolving outlook. Although gravity is the ultimate driving force for star formation, modern ideas and observations reveal that the process is regulated by strong magnetic fields and their associated wave modes. We present detailed numerical and semi-analytic models which lend weight to this picture. New observations at high spatial and spectral resolution are confronting the theory, and promise to lead the way in the next decade. We also discuss some of the key unresolved issues in this field of research.

Gravity Probe B - A Mission To Measure Space-Time

Since 1959 Stanford University has designed and developed a spaceborne gyroscope experiment to test two predictions of general relativity. Under the influence of the mass and spin of the earth the spin direction of the gyroscopes in low earth-orbit is expected to display geodetic and gravito-magnetic precession with respect to an inertial frame of reference. A telescope on board the spacecraft will allow the motion of the gyroscope's spin direction to be measured with respect to a bright guide star. Very-long-baseline interferometry observations by Harvard University and York University are being used to measure the star's proper motion with respect to the (quasi) inertial extragalactic reference frame. The mission, considered NASA's last ``big one'' is scheduled for launch in the year 2000. I will discuss the mission, the experiment, the VLBI observations and the accuracies with which the two predictions and thus the curvature and rotation of space-time can be measured.

Magnetic Fields, Charged Particles and Quantum Mechanics

Many years ago, Aharonov and Bohm discovered some interesting properties of the electromagnetic potentials in their theoretical study of quantum mechanical treatment of these fields¹. They showed that there is an observable effect of electromagnetic potential on a charged particle even in the region where all the fields vanish. This non-classical effect is called as the Aharonov-Bohm effect. I will re-examine the quantum mechanical treatment of a charged particle in a magnetic field. The "theoretical origin" of the Aharonov-Bohm effect within the limits of quantum mechanics will be discussed. It will be shown that a test of the above effect is also a test of some fundamental concepts of quantum mechanics. The quantal phase factor which is seen in the Aharonov-Bohm effect has become a popular subject of research. A brief discussion of this subject will also be presented.
¹(Y. Aharonov and D. Bohm, Phys. Rev. 115, 485 (1959)).

Solar Forcing of the Mesopause Region Thermal Structure

Most observations of middle atmosphere temperatures have been restricted to single rocket profiles, nighttime lidar measurements, and daytime limb scanning measurements from satellites. This limitation in diurnal coverage has inhibited studies of thermal tides in this region. In 1996 the University of Illinois Na wind/temperature lidar was modified for daytime observations. The instrument was then used to measure middle atmosphere temperatures (80-105 km) throughout the diurnal and annual cycles at the Urbana Atmospheric Observatory (40N). In this paper, these data are compared with the tidal predictions of the NCAR Global Scale Wave Model and used to assess the import of solar forcing of the mesopause region thermal structure. We show that the diurnal oscillations in temperature are dominated by solar UV absorption by O2 above 100 km (~3 K amplitude @ 102 km) , solar UV absorption by O3 below 92 km (~5 K amplitude @ 85 km), and by chemical heating (~1.5 K amplitude @ 96 km) and propagating tides between 92 and 100 km. The observations reveal a distinct minimum in the 24 h amplitude near 96 km which appears to be associated with the destructive interference between the chemical heating and propagating tide which are both maximum near midnight at this altitude and the solar UV heating in the lower thermosphere which is maximum near noon. Observations with this same lidar at Starfire Optical Range, NM during the 1998 Leonids meteor shower are used to illustrate the direct effects of chemical heating in long-lived meteor trails. Between 90 and 95 km, chemical heating, quenching, and the diurnal tide all have maxima at night and appear to responsible for the strong temperature inversion layers reported from past nighttime lidar campaigns. 

Departmental Seminars Fall 1998: Abstracts

Ice Chemistry in the Outer Solar System

The moons of Jupiter, Saturn, Uranus and Neptune contain water ice and other condensed volatiles on their surfaces. These satellites are subjected to irradiation from the naturally occurring plasma ions that inhabit Jupiter's magnetosphere. As a result, some exotic surface chemistry may occur in the ices, leading to complicated organic molecules. Also, the influx of radiation will cause changes in the crystalline structure of the ice. The special case of Ganymede, which has its own magnetosphere, results in a unique regional ice physics. This ice physics and chemistry on the satellites will be discussed.

Physics Education in Ontario Schools: New Directions in Curriculum

This fall, a new (made at York) science curriculum for Grades 1-8 goes into effect and next September the new curriculum for High Schools will begin to be implemented. These new curricula aim to ensure that standards for science specialists will not only be at least as high as in the past but that, in addition, all students will have a greater degree of scientific literacy than before. This talk will describe the structure and purposes of both new curricula and I will share draft material for the Grade 11-12 Physics program, which is still in development, for comment.

High-Precision Microwave Measurements of the n=2 ³P₁ to n=2 ³P₀ and n=2 ³P₁ to n=2 ³P₂ Intervals in Atomic Helium - Progress Toward a Better Measurement of the Fine Structure Constant

The best measurement of the fine-structure constant (alpha ~1/137) is presently made by comparing high-precision QED calculations and precision measurements of the anomolous moment of the electron (g-2). These measurements yield a value of alpha at a level of precision better than 20 parts per billion (ppb). An alternate (and more obvious) way of measuring this fundamental constant is with high-precision measurements of fine-structure intervals in simple (calculable) atomic systems. The n=2 ³P intervals of Helium offer such an opportunity. QED calculations of these intervals are presently at the level of precision of ~600 ppb in the interval and hence ~300 ppb in alpha. Expected improvements in this theory will soon be at such a level as to make high-precision measurements of these intervals a more accurate measure of the fine-structure constant alpha. Our measurements of these intervals are done as follows. An intense thermal-beam of metastable helium n=2 ³S₁ atoms (>10¹⁵ /sec/steradian) is created in a DC discharge. The beam is optically pumped using an IR diode laser at 1.083 microns (which is locked to the atomic resonance in an RF discharge cell) into the m=+1 and m=-1 metastable states (thus emptying the m=0 state). These atoms are then excited to the 2 ³P₁ m=0 state using a second diode laser (locked to a second cell). Immediately following this (in less than 98 ns, the lifetime of the n=2 ³P states) the atoms enter a waveguide (or coaxial line) where microwaves at 29.6 GHz (or 2.3 GHz) excite the atoms up to the n=2 ³P₀ state (or down to the n=2 ³P₂ state) in a microwave field of 29.6 GHz (or 2.3 GHz). Atoms in these states can decay to the m=0 metastable state. The m=0 atoms are detected by another laser excitation up the the ³P₀ m=0 state and collecting the resulting femptowatt flourescence. The ³P₁ to ³P₀ interval is measured to be 29.616966 (13) GHz. Progress toward a kHz measurement of the ³P₁ to ³P₂ interval will also be presented. The results will be compared to previous microwave and laser measurements of the intervals and to theoretical predictions for the intervals.

High-intensity Light-matter Interactions

This contribution reviews laser-matter interactions in the visible and UV spectral range using nanosecond and femtosecond pulses. The intensity range of 10⁶ up to 10²⁰ W/cm² is covered with typical examples from linear and nonlinear optics, and plasma physics such as the production of higher harmonics. Both the necessary experimental equipment and novel developments, such as vacuum polarization and pair-production, will be dealt with.

Ruminations of a Skeptic: When thinking goes awry

In the laboratory (or observatory) at least, scientists are "skeptics," demanding compelling evidence before accepting any claim. Such standards, however, are often abandoned when it comes to addressing some important issues in society and is largely responsible for the rise of the "new irrationality" at the end of the 20th century. This talk will describe in some detail and with lots of examples those pseudosciences and paranormal beliefs that have come to be so popular in contemporary society - from astrology to UFOs - why we as scientists should be so concerned, and what we as informed citizens can do to stem their tide.

Diamond Detectors for Future Particle Physics Experiments

Future discoveries in particle physics will rely on the operation of detectors in increasingly hostile radiation environments. All of the large general purpose particle physics experiments today rely on silicon microstrip sensors to precisely measure the event topology very near the interaction region. As beam intensities increase, in the search for rarer and rarer physics these silicon sensors will be damaged. The search is on for an alternative material. Diamond is nearly ideal for such purposes. Its outstanding radiation hardness, fast charge collection and low leakage current allow it to be used in high radiation environments. These characteristics make diamond detectors particularly appealing for use in the next generation of microstrip trackers. Over the last 7 years we have worked with manufacturers to develop Chemical Vapour Deposited (CVD) diamond substrates capable of detecting charged particles. The manufacture of this CVD material and some of its properties will be described briefly followed by results from several devices which show the possibilities of using diamond in a high energy physics experiment.

Destroying Disks Around Young Stars: Photoevaporation in the Orion Nebula

In this talk I will discuss the various methods by which disks around young stars can be destroyed: wind stripping, accretion, encounters, and photoevaporation. I will then focus on photoevaporation in the Orion Nebula where the strong UV radiation field produced by the central O stars in the Trapezium cluster create a hostile environment for the young low-mass stars and their disks. The talk will end with a discussion of the present state of the disk systems and their evolution, complete with speculation on the likelihood of planet formation. For more information see: http://www.cita.utoronto.ca/~johnstone/orion.html

Helium Fine Structure and the Fine Structure Constant

The fine structure constant is one of the fundamental parameters of the standard model. It can be determined with varying precision in quite a few ways, among which are quantum electrodynamics (QED) determinations. These involve comparing high-accuracy experiments with the predictions of QED, which involve a power series in the fine structure constant, assuming the correctness of QED, and inferring a value for the constant. The fine structure of helium is one case that allows this kind of determination: the challenges posed to experiment and theory to reach a useful level of accuracy will be discussed.

Two-stage Rydberg Charge Exchange: An Efficient Method for Production of Antihydrogen

Recent advances by G. Gabrielse at Harvard University have allowed for the trapping and cooling to 4^o K of both antiprotons and positrons. We have recently proposed a novel scheme for producing antihydrogen from these cold trapped constituents and are starting to collaborate with the Harvard group in implementing the scheme. In the scheme, cesium atoms which are laser excited up into highly-excited (Rydberg) states collide with trapped positrons to produce Rydberg states of positronium. This positronium then collides with trapped antiprotons to produce Rydberg states of antihydrogen. Because the antihydrogen atoms would be cold, they could be trapped by a magnetic field.

Convection Patterns

Fluid convection makes a nice laboratory-scale system in which to study the formation of regular patterns under nonlinear, non-equilibrium conditions. I will describe recent experimental work on several species of convection, occurring in a variety of fluids. I will describe experiments on Benard-Marangoni convection in layered isotropic fluids, which are aimed at understanding large, 2d patterns and pattern transitions. A much simpler flow pattern occurs in thin films of smectic liquid crystals, in which the fluid motion is highly constrained. Here, the flow is driven electrically, which allows a novel sheared annular geometry which is not possible in thermal convection. Finally, I will describe an experiment on convection-driven fingering of a propagating chemical reaction front.

Where Did All the Antimatter Go?

Why are there so many more protons than antiprotons in the universe? In 1967, Andrei Sakharov proposed three conditions which would allow this cosmic matter-antimatter asymmetry to evolve from the symmetric state immediately after the Big Bang. One of these conditions was that certain fundamental symmetries in the interactions of elementary particles, namely the combination of charge-conjugation (C) and parity-inversion (P), are violated at a fundamental level. In the theory of the weak interactions of quarks, this so-called CP Violation manifests itself through a complex matrix, called the Cabibbo-Kobayashi-Maskawa (CKM) Matrix, which parameterizes the mixing of the quark states. The CKM Matrix is a fundamental part of the Standard Model of quarks and leptons and it is therefore crucial that we experimentally probe it. In this talk I will discuss how the CKM Matrix has arisen naturally from Fermi's original theory of proton beta decay to our present understanding of the interactions of the six fundamental quarks. I will define just what CP Violation is and show how it is a natural by-product of the "phase" of the CKM Matrix. I will then describe experiments presently under construction and those that have been proposed to measure this phase and, hopefully, see new physics beyond the CKM Matrix. I will close with a brief overview of what the future holds.

Ion Traps: Can We See a Single Ion?

Although we know that matter is made up of individual atoms, how many of us can truly claim to have seen an atom, let alone studied one particular atom for several seconds, minutes, or even hours as it interacts with the world around it? The advent of the ion trap, and in particular the Paul Trap, has made this possible. This talk will present a brief history of rf-quadrupole ion traps and provide some background theory about both ion trapping and laser cooling. The capabilities of these traps will be illustrated through descriptions of some ion trap experiments that have been carried out over the last decade at the Max-Planck-Institut für Quantenoptik in Garching, near Munich, Germany. This will included some experimental studies of MgC₆₀⁺ complexes generated and analysed in a linear ion trap, which will be continued in the new laboratory at the University of Calgary.

SPEAKER:Prof. James L. Pinfold
ORGANIZATION: University of Alberta - Centre for Subatomic Research

The ALTA Project and the Mystery of Ultra High Energy Cosmic Rays

This talk, which is aimed at the non-specialist, starts with a very brief description of the development of the detection techniques for high energy cosmic ray showers. Over the last 30 years or so a handful of events have opened a window to the field of high energy astrophysics and particle physics. These events have energies exceeding the so-called GZK cutoff. The nature of these Ultra High Energy Cosmic Ray Events (UHECREs) is essentially unknown and no known accelerating mechanism is widely considered as being able to explain their production and propagation to Earth. A description of these UHECREs will be given along with the various theoretical models and future experiments that attempt to illuminate the mystery of ultra high energy cosmic rays. Last, but not least, the ALTA project will be described. This project will utilize over 20 Alberta high-schools and colleges as the nodes of an extremely large area (roughly 20,000 km²) sparse cosmic ray shower detector array. The physics objectives of the array will be discussed and related to the search for UHECREs. The unique educational opportunities that this project presents will also be described.
[Note: ALTA and similar efforts in the U.S. were written up in the October Issue of Physics Today]

Financial Markets and Arbitrage

We will discuss the existence of arbitrage opportunities in various financial markets. An arbitrage opportunity is a riskless plan to make profits without investments.

Applied Electron Dosimetry

The influence of ionizing radiation on living systems is at the heart of the practices of radiation protection and medical applications. Dose is traditionally used as a correlate in assessing the impact of exposure to such radiation. Electrons, whether generated in an accelarator or produced in radioactive decay are commonly used in certain therapies. In this talk the general problem of radiation transport and dose assessment will be reviewed. A combination of analytical, computational and experimental work attempting to contribute to our understanding of the problem, particularly with respect to interfaces will be discussed. Applications to therapeutic methods designed to confront restenosis (arterial closure), cancer and rheumatoid arthritis will be described. The special problem arising at low energies will be mentioned with particular reference to tritium.

Migrating Planets

A planet orbiting in a disk of planetesimals can experience an instability in which it migrates to smaller orbital radii. Resonant interactions between the planet and planetesimals remove angular momentum from the planetesimals, increasing their eccentricities. Subsequently, the planetesimals either collide with or are ejected by the planet, reducing the semimajor axis of the planet. If the surface density of planetesimals exceeds a critical value, corresponding to approximately 0.03 solar masses of gas inside the orbit of Jupiter, the planet will migrate inward a large distance. This instability may explain the presence of Jupiter-mass objects in small orbits around nearby stars.

The Canadian & International Physics Olympiads

The International Physics Olympiad (IPhO) was founded thirty years ago in Eastern Europe. Canada participated for the first time in 1985 and now there are over 60 countries involved. The annual competition is for teams of high school students. Details of the Canadian Olympiad program and our International results will be discussed. Canada acted as the host nation in 1997. The event was held at Laurentian University in conjunction with Science North. Inco Limited was the main sponsor of the 1997 IPhO providing $160,000 towards its $500,000 budget. A description of this succesful event will be presented. The Olympiad has the full support of the Canadian Association of Physicists.

Status of the Search for Dark Matter

The fact that a large part of the mass of the universe is of unknown nature is widely recognized as one of the main open questions in astro-particle physics. Current models explaining the evolution of the universe and the slight anisotropy of the cosmic background radiation have in common that they predict an appreciable contribution of non-luminous, non-baryonic matter in the form of a mixture of relativistic, light particles and non-relativistic, massive particles (so-called Hot and Cold Dark Matter). Accelerator experiments and results from the first round of Dark Matter experiments have explored, up to now, only a small range of masses and types of possible candidates. Several new initiatives worldwide aim at a substantial improvement in sensitivity. One of these is the PICASSO project at the University of Montréal, which uses droplets of moderately superheated liquids as detection medium for Cold Dark Matter induced nuclear recoils. In this talk I will give an overview on the present status of Dark Matter searches and discuss first results obtained with a 5g protype of the PICASSO project.

The Discovery of Two Distant Moons of Uranus

Observations taken at the Hale 5-meter telescope on Palomar Mountain in early September have found two objects closely following Uranus. After continuing follow-up observations, the objects are known with virtual certainty to be two new distant satellites of Uranus. According to current best-fit orbits be determined from the available observations, the brighter object is moving along a highly eccentric and inclined path that is more than 8 million km from Uranus; the fainter object travels more than 6 million km from the planet. That is, respectively, they lie more than 300 and 200 planetary radii out. Both appear to be in orbits retrograde with respect to the planet's motion around the Sun; thus these are the first two known IRREGULAR satellites of Uranus. Each of the other giant planets in the outer solar system has been known for some time to possess irregular satellites. The diameters of the new satellites are estimated to be 120 km and 60 km, assuming that they reflect about 7 percent of the sunlight striking them. Prior to these discoveries, Uranus had been thought to have 15 moons, five of them identified by ground-based telescopes (the last in 1948) and ten found by the Voyager spacecraft during its 1986 flight through the system. I will discuss the history and future implications of this discovery.

Planting RICE in the Antarctic Icecap or
Whatever happens to all those antennas that disappear from new cars?

Cosmic rays have historically been the source of much of our information about the extraterrestrial world. It is believed that among the most energetic cosmic rays are those which may be produced by massive black holes which could exist at the centers of some galaxies (aka `Active Galactic Nuclei', or AGN). Additional ultra-high energy neutrinos may be produced by the (as-yet-unidentified) process responsible for the ultra-high energy cosmic rays observed in present Extensive Air Shower experiments, and anticipated for the future Auger Project. The Fly's Eye Experiment in Utah has confirmed that particles of energy as high as 10<sup>20</sup> eV are, indeed, present in the cosmic ray flux. We describe a new experimental effort to detect ultra high energy electron neutrinos through their interactions with ice molecules in the Antarctic icecap, based on the principle of `radio coherence'. Experimentally, we measure a long-wavelength (radiofrequency) pulse resulting from this interaction. A prototype experiment (Radio Ice Cerenkov Experiment, or RICE) presently operating at the South Pole is described. This experimental effort has been made possible only through the cooperation, assistance, and support of the AMANDA collaboration.

Physics at the Next Linear Collider

The Standard Model of elementary particles and their interactions provides a very accurate description of all current measurements. Yet, it is only considered to be a low energy approximation to a deeper more fundamental theory. Uncovering the next level of understanding, whether it be Grand Unified Theory, Supersymmetry, Technicolour, or something else, is the next step towards understanding the building blocks of the universe. In my talk I will give an overview of the Standard Model and Beyond and show how the Next Linear Collider, a high energy e⁺e^- collider, can search for physics beyond the Standard Model.

Fighting the Split Brain: Why Renormalization is a Good Thing

The incompatibility of General Relativity and Quantum Mechanics - both of which have strong experimental support in their respective regimes - is often lamented as one of the great failures of modern physics. I argue in this talk that this incompatibility is not so drastic, and that General Relativity and the Standard Model of particle physics together provide an excellent quantitative *quantum* description of all physics - including gravity - over the complete range of distance scales we understand. This perspective follows from the modern picture of the physics which underlies renormalization. It provides a powerful, unified point of view whose application has borne fruit in many branches of physics.

Purpose

• Physics is GOOD for you!
• Magic, the ancestor of science, differs from physics in several respects. The relationship between the two will be explored.
• While no great secrets of magic will be revealed, some underlying physical principles will be explained.
• If time allows, a bit of magic will be taught.
• Magic is GOOD for you!

Program

• The linking rings and Maxwell' equations.
• Pepper's ghost and other virtual images.
• The principle of misdirection done with coins.
• The table cloth trick done poorly.
• Fluid statics.
• Matter-antimatter annihilation in the bare hands.
• Multiplying balls
• Houdini's famous razor blade trick done with light bulbs.
• Vector ropes.
• The Professor's Nightmare.

Is Nuclear Physics Finished?
Lessons from History - Chalk River

The story of Nuclear Physics at Chalk River spans the glory days of Nuclear Physics. How did Canada through Chalk River contribute to that glory? If those who do not learn from history are condemned to repeat it, what have we learned from the history of Nuclear Physics at Chalk River? But if we are to learn from history, we must first know it. This talk will attempt to summarize the story of one laboratory, and in so doing convince you of the magnificent contribution Chalk River made to physics.

The Dyslexic Neutrino

Neutrinos comprise fully one quarter of the elementary constituents of our universe yet, because they interact so weakly with matter, little is known of their properties. In the standard model of elementary particles, neutrinos are considered massles yet there are theoretical motivations (e.g., neutrinos as the dark matter in the universe) and some experimental hints, particularly from neutrinos resulting from cosmic rays interacting in the upper atmosphere, that neutrinos do, in fact, have a small mass. If they do have mass, then we should be able to observe a fascinating quantum mechanical effect known as neutrino oscillations. In this talk I will describe the formalism of neutrino oscillations and briefly review the experimental evidence for neutrino mass. I will finish by describing an experiment planned for early next century to definitively observe neutrino oscillations. A beam of neutrinos is to be created at the Fermi National Accelerator Laboratory near Chicago and pointed towards the Soudan mine located some 730 km north in Minnesota. An 8 kton detector is to be installed in the mine which should be sensitive to oscillations due to very small neutrino masses. Such a finding would cause a fundamental change in the standard model of particle physics.

Extrinsic and Intrinsic Piezoelectricity
 

• Intrinsic piezoelectricity.
• Extrinsic piezoelectricity in ferroic materials.
• Available facility for for electromechanical measurements at the Technical University of Liberec.
• Organization of Physics education in Liberec.

Putting the Q Back into Cavity QED

Cavity QED allows quantum electrodynamics to be tested in the regime where the number of electromagnetic field modes can, in principle, be reduced to one. For a high-finesse cavity and strong dipole coupling between a two-level atom and the field, entanglement between the internal degrees of freedom of the atom and the cavity field should yield genuine quantum effects not explainable by the semiclassical theory of radiation. However, such experiments are notoriously difficult. We investigate what is necessary in order to observe genuine quantum signatures for the entangled system.

ABSTRACT: Chemistry In The Outer Solar System

TBA

DATE: 16 Sept 97
SPEAKER: Paul Wiegert
ORGANIZATION: York University

ABSTRACT:The Earth Companion Asteroid 3753 (1986 TO)

TBA

DATE: 23 Sept 97
SPEAKER: Helen Freedhoff
ORGANIZATION: York University

ABSTRACT: Fluorescence By An Atom In An Intense Resonant Field: The AC Stark Effect
 

ABSTRACT: Generation Of Electric Currents In Unbiased Semiconductors Using Optical Coherence Control

TBA

ABSTRACT: Optimized Potential Model For Atoms And Molecules

TBA

ABSTRACT: Should We (Still) Be Concerned About Greenhouse Warming?

TBA

ABSTRACT: The Structure and Photoelectron Spectrum of Niobium Cluster Anions Studied by Density Functional Theory

I will first give a quick overview of the Linear Combination of Gaussian Type Orbitals Kohn-Sham (LCGTO-KS) method, and some results that we obtained with it over the past few years. Then I will discuss its applications to n-atom Nb cluster anions (n=3--8). We did extensive search for the lowest energy isomers and confirmed our findings by comparing to photoelectron spectra. I will show our calculated optimum geometries, vibrational frequencies, and electron binding energies (BEs) for different cluster isomers. I will describe two simple ways to account for final state effects on BEs, based on Slater's transisition state method, which give results consistent with one another and with experiment. The jellium model does not describe properly the electronic structure of these clusters but it is nevertheless useful for understanding certain trends.

ABSTRACT: Testing Gravity's Foundations

The equivalence principle is foundational to our understanding of gravity. It implies that all forms of matter and energy couple to gravity in the same way. As a consequence, it allows us to interpret gravity as a manifestation of the curvature of space and time. Although elegant and beautiful, the equivalence principle is not a logically necessary postulate, and must be experimentally checked. I will review our current understanding of the equivalence principle and then describe some ideas for testing it in several new ways at the subatomic level. These include new measurements of magnetic moments of the electron and muon, atomic energy shifts, neutrino oscillations and Kaon and B-meson decays.

ABSTRACT: Astronomy and Physics Education: Why, What and How?

Education is important for science because it affects the recruitment and training of the next generation of scientists, and it affects the awareness, understanding, and appreciation of science by the taxpayers and decision-makers who support us. Science education also promotes science literacy, which is essential to the health of our economy, our environment, our bodies and minds, and even our culture. The present state of science education and literacy in Canada is far from perfect at every level. Why? We know a great deal about how to teach and learn science effectively, but do we have the political will to implement this knowledge? Do we need to throw more money at the problem, as is happening in the US? And who is responsible? I will argue that we all are. In this presentation, I will give an overview of science education from kindergarten to Elderhostel. Many of my examples will be drawn from my own discipline of astronomy, but they should be "universally" applicable. I will suggest (explicitly or implicitly) some things that you, your department, your university, and your other scientific and educational organizations can do to promote more and better science education in your community and around the world. These actions will not only be beneficial, but they will also be fun!

ABSTRACT: How We Came To Know That Space and Time is Curved

Our modern undertanding of the physics of gravitation as "curvature" in the four dimensional Riemannian manifold of "spacetime" is one of the major developments in Physics this century. This spectacular achievment was made possible by a grand synthesis, begun by Albert Einstein in 1916 but still actively pursued today, of the contributions of many researchers in the fields of both mathematics and physics. This colloquim will examine the history of that synthesis beginning with Euclid's Mathematics and Galileo's Physics and will trace its development up through Gauss, Riemann, Ricci, and Levi-Civita as well as through Newton, Maxwell, Lorentz, Minkowski, and Einstein. This Colloquium will be presented with a minimum of Tensor Calculus and Differential Geometry and will be suitable for a general audience.

ABSTRACT: A Monte Carlo Renormalization Group approach to Scaling

The critical region near a second order phase transition is characterized by a diverging correlation length as the critical point is approached. Although a qualitative understanding of the physics of this divergence in the critical region was reached in the 1970's with the advent of the renormalization group, no calculational technique yet exists which can match the accuracy achieved in a recent experiment on superfluid helium on the space shuttle.

I will describe how the divergence of the correlation length can be viewed as the purely geometric expansion of self-interacting but otherwise random walks of increasing length and review the renormalization group picture that explains the universality and qualitative details of the expansion. I will conclude with a summary of a recent Monte Carlo implementation of the renormalization group for a model in the Self-Avoiding Walk universality class. The high accuracy of the results suggest it may be possible to develop the technique for a significant test of the helium measurements.

ABSTRACT: Lattice Gauge Theory for Dummies

The rationale for and the method of simulating the quantum field theory of strongly interacting quarks, quantum chromodynamics (QCD) on a space-time lattice is presented.

ABSTRACT: Close Encounters of the Electro-Weak Kind: New results from HERA

Ninety years ago Rutherford found the atomic nucleus by studying head-on collisions between the highest energy probe particles available to him and heavy atoms. His probes were alpha particles emitted by naturally radioactive substances, but the Rutherfords of today scatter electrons from quarks at the HERA collider facility in Hamburg. HERA provides much higher energies, and we probe much more deeply. I will describe our experiment at HERA, discuss its recent results in the context of what has been learned from the last 90 years of high energy particle physics experimentation, and show that once again the observed behaviour is beginning to deviate from the expected.