Physics Colloquia Spring 2012

(usually Fridays 2:00 PM in SE 319)

Titles link to the abstracts.

Date Speaker Title
Feb 17
 Zhigang Chen
(San Francisco St U)
Feb 24
 Steve Detweiler
(U of Florida)
3:30 Wed
Feb 29
Barbara Whitney
(Wisconsin / SSI)
Mar 9
 Spring Break  
Mar 16
 Lars Hernquist
(Harvard)
3:30 Wed
Mar 21
Jiasheng Huang
(Harvard-Smithsonian)
Apr 13
 Saskia Mioduszewski
(Texas A&M)
Apr 20
 Olga Malkina
(FAU)
   

Colloquium Abstracts

Optical control with specially-engineered photonic lattices and beams
Zhigang Chen (San Francisco State University), February 17, 2012
Light propagation in periodic structures or in free-space with intelligent beam design exhibits many intriguing phenomena with new opportunities for controlling the flow of light and related applications. In this talk, I will provide a brief overview of our recent work on spatial control of light propagation in optically induced photonic lattices, and optical control and manipulation of particles with various specially-designed optical beams including particle trapping and rotation with optical propelling beams, nano- and micro-aerosol trapping and transporting with optical bottle beams, optical control and manipulation with self-accelerating and auto-focusing Airy beams, and self-trapping and self-induced transparency in nonlinear nanosuspensions. This work was supported by US National Science Foundation and Air Force Office of Scientific Research.
 
Black Holes and Gravitational Waves
Steve Detweiler (University of Florida), February 24, 2012
( Note: New location in SE 319)
John Wheeler coined the name "Black Hole" in 1967. Ever since, these unusual objects have been invoked to explain a surprisingly diverse range of phenomena. Today we apparently observe black holes with a wide variety of masses and in many different environments. However we have rather scant evidence that these objects are actually the black holes of General Relativity rather than, say, small massive object which do not obey the rules of Einstein's gravity. Gravitational waves indirectly provide explanations for a different set of phenomena. However, their direct detection continues to be a rather elusive goal. It is possible that sometime soon (five to ten years?) gravitational waves will indeed be detected, and perhaps this event will give us direct evidence that the black holes which we observe today are indeed the black holes of Einstein's gravity.
 
Dust Radiation Transfer and Star Formation
Barbara Whitney (Wisconsin / SSI), February 29, 2012
( Note: special time and place, Wednesday, February 29, 3:30–4:30, SE 319)
Star formation is the engine that powers galaxies throughout the universe. The star formation rate of a galaxy is an important cosmological parameter, determining galaxy evolution and lifetimes. Star formation can be studied on many scales from a global, galactic level to detailed observations and modeling of single sources. I will show how radiation transfer models can be used to interpret data on star formation at all these levels.
 
Cosmology on a Moving Mesh
Lars Hernquist (Harvard), March 16, 2012
Understanding the formation and evolution of galaxies in a cosmological context using numerical simulations remains an elusive goal. In this talk, I describe a new approach to modeling the hydrodynamics of galaxy formation in which the equations of motion are solved on a moving mesh. The use of a moving mesh makes the scheme fully Lagrangian, unlike popular particle-based codes which are quasi-Lagrangian in nature, and mitigates against advection errors when a spatially fixed grid is used. I present results from an initial study comparing results for a moving mesh with those obtained using a smoothed particle hydrodynamics solver. This preliminary work suggests that the new approach offers promise for resolving the long-standing problems which have plagued this field for nearly two decades.
 
Red Galaxies at High Redshifts: Dusty or Passive Galaxies?
Jiasheng Huang (Harvard-Smithsonian Center for Astrophysics), March 21, 2012
( Note: special time and place, Wednesday, March 21, 3:30–4:30, SE 319)
I will present recent detection of IRAC sources in the CANDEL fields with an extremely red color of H-[3.6]>4.5. We find that only 3 types of SED templates can produce such a red H$-$[3.6] color: a very dusty SED with the Calzetti extinction of Av=16 mag at z=0.8; a very dusty SED with the SMC extinction of Av=8 mag at z=2.0~2.2; and an 1Gyr SSP with Av~0.8 at z=5.7. We argue that these sources are unlikely dusty galaxies at z<2.2 based on absent strong MIPS 24um emission. The old stellar population model at z>4.5 remains a possible solution for these sources. At z>4.5, these sources have stellar masses of Log(M/M_sol)=10.6~11.2. Some of those sources are also detected at FIR and X-ray, indicating that they are ULIRGs/QSOs This suggests a galaxy-merging scenario for the formation of these massive galaxies at high redshifts.
 
Probing High-Temperature QCD Matter
Saskia Mioduszewski (Texas A&M), April 13, 2012
The Relativistic Heavy-Ion Collider (RHIC) has been providing collisions of Au ions at ultra-relativistic energies since 2000. Nuclear physicists from around the world have been studying the matter created in these collisions. I will present some recent results and focus on experimental methods used to gain insight into the properties of the so-called Quark Gluon Plasma.
 
(Title to come)
Olga Malkina (FAU), April 20, 2012
(Abstract pending)