Talks

The existence of dark matter is hardly in doubt, yet astrophysicists continue to search in vain for any non-gravitational signals of it. In the case of weakly interacting massive particle (WIMP) models, ongoing annihilation or decay of WIMPs to Standard Model particles could provide observable signals, e.g. as excess gamma rays in the center of the Milky Way or as excess ionization at high redshift. I will present our latest results on the most rigorous constraint from astrophysics: the effect of WIMP annihilation on the ionization history of the Universe, as recorded in the CMB.

A wide range of results have led to a confusing situation in the area of direct WIMP detection. I'll review the status of these results. The features of the results imply that almost any explanation will require a departure from standard assumptions (Maxwellian halo, elastic WIMP scattering or otherwise) so I'll review the techniques to compare experiments without appealing to these assumptions. In particular, I'll comment on the status of light WIMPs and the iodine interpretations of DAMA (such as inelastic dark matter) in light of the most recent results.

A charged particle can detect the presence of a magnetic field confined into a solenoid. The strength of the effect depends only on the phase shift experienced by the particle's wave function, as dictated by the Wilson loop of the Maxwell connection around the solenoid. In this seminar I'll show that Loop Gravity has a structure analogous to the one relevant in the Aharonov-Bohm effect described above: it is a quantum theory of connections with curvature vanishing everywhere, except on a 1d network of topological defects. Loop states measure the flux of the gravitational magnetic field through a defect line. A feature of this reformulation is that the space of states of Loop Gravity can be derived from an ordinary QFT quantization of a classical diffeomorphism-invariant theory defined on a manifold. I'll discuss the role quantum geometry operators play in this picture, and the perspective of formulating the Spin Foam dynamics as the local interaction of topological defects.

The Large Hadron Collider (LHC) is now running (after a rocky start). This talk reviews why the start was rocky and how this constrains the physics program over the next few years. I will briefly survey how 'naturalness' arguments argue why something should be discovered, and why theoretical proposals fall into three main categories. If time permits I will close by telling you why I think the cosmological constant problem implies the LHC will strike paydirt and make quantum gravity an experimental science.

We perform an exact localization calculation for the expectation value of Wilson-'t Hooft line operators in N=2 gauge theories on S^1 x R^3. The expectation values form a quantum mechanically deformed algebra of functions on the Hitchin moduli space by Moyal multiplication. We demonstrate that these expectation values are the Weyl transform of the Verlinde operators, which acts on conformal blocks as difference operators. Our results are also in exact match with the predictions from wall-crossing in the IR effective theory.

With a background in computer and systems engineering as well as language processing and automatic speech recognition, Ms. Payette was selected from a pool of 5,330 candidates to become a Canadian astronaut, focusing on technical issues in robotics. Today, following her amazing professional career and numerous life experiences, Ms. Payette is veteran of two missions to the International Space Station as a crew member and Flight Engineer. She also holds a commercial pilot license; earned military pilot captaincy on the 'Snowbird' jets; is a certified deep-sea diving suit operator; is fluent in French and English, and can converse in Spanish, Italian, Russian and German. She has received many awards, holds numerous degrees and, on a personal note, plays the piano and has sung with the Montreal Symphony Orchestra, the Piacere Vocale in Basel, Switzerland, and the Tafelmusik Baroque Orchestra in Toronto. Drawing from her many firsthand experiences and zest for life, Ms. Payette will share an astronaut's high level perspective on extraordinarily complex, yet highly collaborative, challenges in space - from both a research and international diplomacy policy point of view.