Department Colloquia

Antiferromagnetism in the Hubbard Model with Ultracold Atoms

Speaker: 
Randall Hulet, Rice University Texas, USA
Event Date and Time: 
Thu, 2014-09-11 16:00 - 17:00
Location: 
Hennings 201
Local Contact: 
Ian Affleck
Intended Audience: 
Undergraduate
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.

Spinning Atoms with Light: a new twist on atom optics

Speaker: 
Bill Phillips, NIST Gaithersburg
Event Date and Time: 
Thu, 2014-04-03 16:00 - 17:00
Location: 
Hennings 201
Local Contact: 
Robert Raussendorf, David Jones
Intended Audience: 
Undergraduate
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.

A Millisecond Pulsar in a Stellar Triple System

Speaker: 
Ingrid Stairs, UBC
Event Date and Time: 
Thu, 2014-03-20 16:00 - 17:00
Location: 
Hennings 201
Local Contact: 
Robert Raussendorf
Intended Audience: 
Undergraduate
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.

Production, Trapping and Spectroscopy of Antihydrogen – the ALPHA Experiment at CERN

Speaker: 
Walter Hardy, UBC
Event Date and Time: 
Thu, 2014-02-27 16:00 - 17:00
Location: 
Hennings 201
Local Contact: 
Doug Bonn, Robert Raussendorf
Intended Audience: 
Undergraduate
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.

Pursuing gravitational waves with Advanced LIGO

Speaker: 
Michael Landry (LIGO observatory), for the LIGO Scientific Collaboration
Event Date and Time: 
Thu, 2014-02-06 16:00 - 17:00
Location: 
Hennings 201
Local Contact: 
Bill Unruh, Robert Raussendorf
Intended Audience: 
Undergraduate
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.

Gamma-ray Astronomy at the Highest Energies

Speaker: 
David Hanna, McGill University
Event Date and Time: 
Thu, 2014-01-30 16:00 - 17:00
Location: 
Hennings 201
Local Contact: 
Mark Halpern
Intended Audience: 
Undergraduate
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.

Does Protective Measurement Tell us Anything about Quantum Reality?

Speaker: 
Amit Hagar, Indiana University, History & Philosophy of Science department
Event Date and Time: 
Thu, 2014-02-13 16:00 - 17:00
Location: 
Hennings 201
Local Contact: 
Robert Raussendorf, Bill Unruh, Philip Stamp
Intended Audience: 
Graduate
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.

The Landscape Problem of Frustrated Magnetism: Has Compelling Experimental Evidence for Order-by-Disorder at Last Been Found?

Speaker: 
Michel Gingras Department of Physics & Astronomy, University of Waterloo
Event Date and Time: 
Thu, 2014-01-23 16:00 - 17:00
Location: 
Hennings 201
Local Contact: 
Marcel Franz
Intended Audience: 
Undergraduate
In some magnetic systems, known as frustrated magnets, the lattice geometry or the competition between different spin-spin interactions can lead to a sub-exponentially large number of accidentally degenerate classical ground states, or false vacuua, and thus a sort of landscape problem for condensed matter physicists. Order-by-disorder (OdD) is a concept of central importance in the field of frustrated magnetism.

How to Find the Needle in the Haystack: Variable Star Lightcurve Classification Techniques

Speaker: 
Andy Becker, University of Washington
Event Date and Time: 
Thu, 2013-12-05 16:00 - 17:00
Location: 
Hennings 201
Local Contact: 
Robert Raussendorf
Intended Audience: 
Undergraduate
Large area surveys such as LSST promise to monitor the variability of billions of stars through repeated imaging, with observations spread across many years and multiple passbands. To fully realize the potential of these data, models for lightcurve classification must be developed that allow inference in spite of data complexity and sparsity. These models must have the flexibility to capture both the prosaic and the novel, and allow users to distinguish one from the other; this capability does not yet exist in a general tool.

Driving Topology, Hunting Majoranas

Speaker: 
Tami Pereg-Barnea, McGill
Event Date and Time: 
Thu, 2014-03-27 16:00 - 17:00
Location: 
Hennings 201
Local Contact: 
Marcel Franz
Intended Audience: 
Undergraduate
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.
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