Mark Raizen
Center for Nonlinear Dynamics and Department of Physics, The University of Texas at Austin
Comprehensive Control of Atomic Motion
The method of laser cooling has opened the door to low temperature physics of dilute gases. Despite the great success of this method, it has been limited to a very small set of atoms in the periodic table and no molecules. I will describe in this talk new approaches to trapping and cooling that have been developed in my group. The first step uses pulsed magnetic fields to stop atoms and molecules where they can be magnetically trapped. The next step is an experimental realization of informational cooling as first proposed by Leo Szilard in 1929 in an effort to resolve the paradox of Maxwell's demon. Together, these provide a two-step comprehensive solution to trapping and cooling. I will describe our progress in applying these new methods to trapping and cooling of hydrogen isotopes. In the short term, we are working to trap hydrogen and deuterium, which will serve as a step towards trapping of atomic tritium. This system will be used for precision measurement of beta decay towards determination of the neutrino rest mass. Our methods are also very applicable to trapping and cooling of anti-hydrogen, and a collaboration at an accelerator laboratory is being pursued.
Mariangela Bernardi
University of Pennsylvania
Massive Galaxies in Massive Datasets
Galaxies have a wide range of luminosities, colors, masses, sizes, surface brightnesses, morphologies, star formation histories and environments. This diversity of properties is not surprising given the variety of physical processes which likely influence their formation and evolution. What *is* surprising is that although the properties we use to describe galaxies span a large configuration space, galaxies do not fill it. Amongst all galaxy families, early-type galaxies - so named because they host the oldest stars - show the most precise regularities in their observed parameters. Their colors, luminosities, half-light radii, velocity dispersions, surface brightnesses, and central black hole masses are all tightly correlated. These correlations encode information about their formation histories, but they can also be used for cosmological studies. I will concentrate on the former, because, for reasons I discuss, understanding why massive early-type galaxies are ``red, dead, metal-heads'' has proved to be difficult. The most recent hierarchical galaxy formation models assume that the stars in early-type galaxies formed in smaller units before they were assembled into a single massive galaxy. This requires a combination of two processes: dry mergers (for the assembly of the smaller units), and AGN feedback to prevent in situ star formation. These processes are most necessary in the most massive galaxies, so I will discuss a number of constraints on massive galaxy formation that come from analyses of Brightest Cluster Galaxies and other extreme objects in the SDSS and other recent astrophysical datasets.
Evelyn Thomson
University of Pennsylvania
Smashing Particles at the High Energy Frontier
Experimental particle physics seeks to understand the fundamental particles and interactions of the universe. I will present the status and future prospects of experimental knowledge for two of these particles: the top quark, the most massive fundamental particle with approximately the same mass as a gold nucleus comprised of 200 nucleons; and the Higgs boson, the most elusive particle as it has evaded detection for over forty years!The results that I will present are based on analysis of data from the current run of the CDFexperiment at Fermilab, which began in 2001 and is expected to continue through 2010. In order to produce massive particles like the top quark, Einstein's famous relation E=mc2 tells us that a lot of energy is needed. Therefore, a beam of protons is accelerated to close to the speed of light and then brought into collision with another equally energetic beam moving in the opposite direction. These collisions occur 1.7 million times per second, and I will discuss how the debris from these collisions is examined for clues about the properties of particles like the top quark and the Higgs boson.
The prospects for the future are dominated by the next generation CERN Large Hadron Collider, located near Geneva in Switzerland, which will reach collision energies up to seven times higher than the FermilabTevatron. In preparation for the first year-long run of the Large Hadron Collider beginning in November 2009, I will also describe the commissioning of the Transition Radiation Tracker, an important part of the giant ATLAS experiment. The Transition Radiation Tracker is essentially a camera with 350,000 channels that takes 75 nano-second long snap-shots of the trajectories of electrically charged particles. The radius-of-curvature of a charged particle's trajectory in a strong magnetic field allows determination of the particle's momentum, while the 100 times brighter signal from transition radiation allows partial discrimination of the least massive charged particle, the electron, from other more massive charged particles.
Gary Gibbons
DAMTP, Cambridge University
Anti-matter in the Looking Glass
I will review some recent and on-going work on the impossibility of of a static equilibrium (stable or unstable) between a matter and antimatter, both in the absence of gravitational forces and when the effects of General Relativity are taken into account. I will cover, black holes, and gravitating magnetic monoples and skyrmions. Some, but not all, of the results have appeared already on the archive as Gravitating Opposites Attract: by R. Beig, G. W. Gibbons, R. M. Schoen, arXiv:0907.119.
Rachel Bean
Cornell University
Testing Gravity on Cosmic Scales
While the properties of gravity, and its consistency with General Relativity (GR), are well tested on solar system scales, within our system and the decay of binary pulsar orbits, they are, by comparison, poorly tested on cosmic scales. This is of particular interest as we try to understand the origins of cosmic acceleration, and whether they are a signature of deviations from GR. Using the latest measurements of the universe's expansion history, twinned with the evolution of large scale structure, we discuss the current constraints on gravity's behavior on the largest scales observable today.
January 13:
Andrea Liu
University of Pennsylvania
Jamming
All around us things seem to get jammed. Before breakfast, coffee grounds and cereal jam as they refuse to flow into our filters and bowls. On the way to work, we are caught in traffic jams. In factories, powders jam as they clog in the conduits that were designed to have them flow smoothly from one side of the factory floor to the other. Our recourse in all these situations is to pound on our containers, dashboards and conduits until the jam miraculously disappears. We are usually so irritated by the jam that we do not notice that the approach to jamming and the properties of the jammed state, in all of these situations, have common properties and similar behaviors that are quite different from those in systems near the liquid-solid transition. I will discuss recent ideas and results that point towards some quantitative commonality between such jamming transitions and one of the oldest and most perplexing phenomena in condensed matter physics, namely the glass transition.
Michael Mann
Penn State University
The Physics of Climate Change
I will review the basic physical principles underlying the behavior of the Earth's climate system, including the role of radiative balance and feedbacks. I will then review the evidence for human impact on climate over the past century, and climate change projections for the next century based on various possible fossil fuel emissions scenarios. I will discuss some of the current limitations in these projections, and will I highlight the role of physics in resolving some of the key remaining uncertainties. I will use as an example the possible role of changes in the El Nino phenomenon in response to human impacts on the climate.
Joanna Aizenberg
Harvard University
Biomineralization: Lessons in Materials Physics
Organisms exercise a level of molecular control over the structure of biomaterials that is unparalleled in today's technology. It is clear that valuable lessons in materials physics can be taught by any organism. I will exemplify this point by describing the underlying physical mechanisms involved in the formation of mineralized tissues in echinoderms and by showing how they can be applied in developing new bio-inspired nano- and microfabrication strategies and devices. The topics will include self-assembly, soft condensed matter, control of crystallization, dynamic optics, and novel actuation systems.
Michael Berry
University of Bristol
Hamilton's Diabolical Singularity
Hamilton’s first application of the concept of phase-space - later so fruitful in physics - was a prediction in optics: conical refraction in biaxial crystals. This was one of the first successful predictions of a qualitatively new phenomenon using mathematics, and created a sensation. At the heart of conical refraction is a singularity, anticipating the fermionic sign change underlying the Pauli exclusion principle and the conical intersections now studied in quantum chemistry. The light emerging from the crystal contains many subtle diffraction details, whose definitive understanding and observation have been achieved only recently. Generalizations of the phenomenon involve radically different mathematical structures.