Events at Physics |
Events on Thursday, February 28th, 2013
- R. G. Herb Condensed Matter Seminar
- Engineering Synthetic Quantum Materials from Cold Atoms: Mott Insulators to Emergent Polariton Crystals
- Time: 10:00 am
- Place: 5310 Chamberlin
- Speaker: Jonathan Simon, University of Chicago
- Abstract: The tools of atomic physics provide a unique and powerful toolbox for studies of quantum many-body physics. Using such systems it has recently become possible to engineer strongly-correlated materials from the ground up and probe them with single-atom resolution. I will describe experiments in which we have synthesized the first magnetic material composed of ultracold atoms, and watched it undergo a quantum phase transition from a paramagnet to an antiferromagnet. I will then introduce a new algorithmic cooling scheme that we have demonstrated, pointing the way to yet more exotic quantum phases that exist at lower temperatures. Finally, I will describe ongoing efforts to develop materials composed of strongly correlated photons whose long-range anisotropic interactions will open new horizons, permitting studies of quantum soft-matter.
- Host: Vavilov & Saffman
- Astronomy Colloquium
- Prospects for X-ray constraints on the local super-massive black hole occupation Fraction
- Time: 3:30 pm - 5:00 pm
- Place: 4421 Sterling Hall
- Speaker: Elena Gallo, Universtiy of Michigan
- Abstract: An issue of crucial relevance in understanding the connection between super-massive black holes and their host galaxies is the "occupation fraction" of massive black holes in the present day universe. While the occupation fraction is expected to be close to 100% in high mass galaxies, predictions differ dramatically at the low mass end, with "light" seeds (i.e. remnants from the first generation of stars) producing a greater nuclear occupation fraction compared to direct collapse models below a few billion solar masses. For an unbiased sample, the local active fraction represents a strong lower limit to the occupation fraction, and X-ray observations of nearby, formally inactive galaxies over a wide range in stellar masses can provide observational constraints to the very mechanism by which the first black holes formed. Adopting a Monte Carlo approach, we make use of the Chandra AMUSE-surveys to characterize simultaneously the black hole occupation fraction and the scaling of nuclear activity with host mass. Further, we discuss future prospects for improving the precision of these parameters as a function of sample size, as well as desired sensitivity and spatial resolution of future missions.
- Host: Prof Elena D'onghia