Events at Physics |
Events on Thursday, September 18th, 2008
- R. G. Herb Condensed Matter Seminar
- Quantum activation, scaling, and quantum measurements
- Time: 10:00 am
- Place: 5310 Chamberlin
- Speaker: Mark Dykman, Michigan State University
- Abstract: Familiar mechanisms of metastable decay are tunneling and thermal activation. We show that periodically modulated systems may display a different decay mechanism, quantum activation. Here, decay occurs via quantum fluctuations induced diffusion over a quasi-energy barrier. We study quantum activation for nonlinear oscillators and show its unexpected features. The decay rate displays scaling behavior near critical parameter values where metastable vibrational states disappear. We also show that the tunnel splitting of symmetric and antisymmetric vibrational states oscillates and changes sign with varying parameters. The results impose limitations on the characteristics of bifurcation amplifiers used in quantum measurements.
- Host: Susan Coppersmith
- Special Astronomy Colloquium at Noon
- The Small Magellanic Cloud Star Formation History
- Time: 12:00 pm
- Place: 3425 Sterling Hall
- Speaker: Elena Sabbi, STSci
- Abstract: The Small Magellanic Cloud (SMC) is a unique laboratory to study a wide range of astrophysical phenomena, from the birth and evolution of stars, through the physics of the multi-phase interstellar medium, to the dynamics and evolution of galaxies. At only 60 kpc from us, the SMC is the closest late-type dwarf galaxy with active star formation. With a present-day metal abundance about a factor eight lower than that of the Sun, the SMC allows to investigate the star formation processes in an environment typical of the formation of the types of galaxies that dominate the appearance of today's Universe. Hence the SMC is an important template for understanding the evolution of galaxies as an astrophysical system.<br>
<br>
The properties of the SMC encouraged us to start a deep imaging survey using the exquisite capabilities of the Advanced Camera for Surveys (ACS) on board of the Hubble Space Telescope (HST) with the objective of investigate the properties of its stellar populations in the bar, the wing and the bridge, in the field as well as in intermediate and old star clusters and in HII star forming regions.<br>
<br>
I will discuss the age-metallicity relation, the three dimensional structure of the SMC halo, the impact of local and global conditions on star formation, and the star formation history of this galaxy over the entire Hubble time, in the context of late-type dwarf galaxy evolution.