Past Department Colloquia

Thu, 2014-09-11 16:00 - 17:00
Randall Hulet, Rice University Texas, USA
Ultracold atoms on optical lattices form a versatile platform for studying many-body physics. We have realized the Hubbard model, a “standard model” of strongly-correlated matter. The Hubbard model consists of a cubic lattice with on-site interactions and kinetic energy arising from tunneling to nearest neighbors. Notably, it may contain the essential ingredients of high-temperature superconductivity. While the Hamiltonian has only two terms it cannot be numerically solved for arbitrary density of spin-½ fermions due to exponential growth in the basis size.
Thu, 2014-04-03 16:00 - 17:00
Bill Phillips, NIST Gaithersburg
Physicists have used light and its polarization to elucidate the internal state of atoms since the 19th century. Early in the 20th century, the momentum of light was used to manipulate the center-of-mass motion of atoms. The latter part of the 20th century brought optical pumping, coherent laser excitation, and laser cooling and trapping as tools to affect both the internal and external states of atoms.
Thu, 2014-03-27 16:00 - 17:00
Tami Pereg-Barnea, McGill
The study of topology in condensed matter is a rapidly growing field. Recent activity ranges from classifying the possible topological systems to first principles calculations of real materials. In this talk I will use a simple language to introduce the subject and survey some recent developments. In the first part of my talk I will present different ways in which a topologically trivial system can be driven into a topological phase. In the second part I will discuss the possibility of observing Majorana fermions in topological superconductors.
Thu, 2014-03-20 16:00 - 17:00
Ingrid Stairs, UBC
Radio pulsars with millisecond rotation rates are "spun-up" by accretion of matter and angular momentum from an evolving companion star. Not surprisingly, most such millisecond pulsars are found in binary systems, typically with white-dwarf companions. Pulsars with more companions are extremely rare, and the examples known to date have involved one or more planetary-mass objects. Recently, my collaborators and I have discovered a millisecond pulsar with two stellar-mass companions. Both companions appear to be white dwarfs, pointing to a unusual evolutionary history for this system.
Thu, 2014-03-13 16:00 - 17:00
Darren Grant, University of Alberta
Scientists have created the world's largest neutrino telescope, the IceCube Neutrino Observatory, in one of the planets most extreme environments at South Pole Station Antarctica. Instrumenting more than a Gigaton of ice, the observatory is designed to detect interactions of the highest energy neutrinos expected to be produced in the Universe's most violent astrophysical processes. With IceCube's recent announcement of the first detection of a diffuse flux of high-energy neutrinos (30 TeV to more than a PeV) of extraterrestrial origin a new window to study the Universe was opened.
Thu, 2014-03-06 16:00 - 17:00
Christine Wilson, McMaster University
The availability of new instruments and telescopes is making it possible to study large, well-selected samples of nearby galaxies at millimeter and submillimeter wavelengths. These observations trace the cold, dense gas and dust which is the fuel for star formation. I will discuss new results from the Herschel Space Observatory from the Very Nearby Galaxies Survey, which aims to observe the closest example of each major class of galaxy with all the photometric and spectroscopic modes that Herschel has available.
Thu, 2014-02-27 16:00 - 17:00
Walter Hardy, UBC
This talk will be partly an update on the status of the ALPHA experiment at CERN, a collaboration of about 40 scientists, more than 1/3 from Canada, and partly a look back at how and why a condensed matter experimenter like myself got involved with antihydrogen research. ALPHA stands for Antihydrogen Laser Physics Apparatus: the goal is to compare the properties of H to H-bar with the highest possible precision, looking for any differences that might shed light on why the universe is made of matter and not antimatter.
Thu, 2014-02-13 16:00 - 17:00
Amit Hagar, Indiana University, History & Philosophy of Science department
An analysis of the two routes through which one may disentangle a quantum system from a measuring apparatus, hence protect the state vector of a single quantum system, reveals that the argument from protected measurement to the reality of the state vector of a single quantum system is circular. Lessons on the available "interpretations" of quantum theory and on the debate on the quantum measurement problem are drawn from this negative result.
Thu, 2014-02-06 16:00 - 17:00
Michael Landry (LIGO observatory), for the LIGO Scientific Collaboration
The Laser Interferometer Gravitational Wave Observatory (or LIGO for short) will detect gravitational waves with second-generation interferometers. At the two observatory sites (Hanford WA and Livingston LA), we have been installing Advanced LIGO detectors since Oct 2010, and are nearing completion.
Thu, 2014-01-30 16:00 - 17:00
David Hanna, McGill University
Gamma-ray astronomy at energies above 100 GeV is a young science where particle physics mixes with astrophysics. In addition to studying high-energy objects such as supernova remnants and active galactic nuclei, researchers look for evidence of dark-matter particle annihilation and violation of Lorentz invariance. Detection of gamma rays from distant sources makes use of Cherenkov light generated by relativistic electrons and positrons in air showers caused by the impact of these gamma rays on the upper atmosphere.
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