Events Archive

Aug
29
2011
Photons do not interact strongly in nature, and have thus been relegated to a role as a tool rather than an object of study in condensed matter physics.However, in cavity quantum electrodynamics, the strong interaction of light with a single atom can lead to strong atom-mediated photon-photoninteractions, even when the light and atomic transitions are not resonant. Recent theoretical proposals have predicted phase transitions in arrays ofthese cavities, demonstrating that complex matter-like phenomena can emerge from a sea of interacting photons. I will present our recent measurements demonstrating strong photon-photon interactions in superconducting cavity QED...
Aug
24
2011
As Goodyear discovered, when he first vulcanized rubber in 1839, a viscous liquid of macromolecules becomes an unusual, utterly random, solid, provided that enough chemical bonds are introduced between the molecules.  Perhaps surprisingly, given the randomness of their architectures, solids formed by the vulcanization process exhibit a number of rather simple and universal features -- both structural and elastic -- that are not exhibited by the apparently simpler, crystalline solids.  In this colloquium, I shall give an overview of current approaches to the physical properties of vulcanized matter and other random-network-forming media, paying special attention to...
Jun
23
2011
Two important advances have occurred in recent years which have brought us closer to the goal of observing and interpreting gravitational waves from coalescing compact objects: the successful construction and operation of a world-wide network of ground-based gravitational-wave detectors and the impressive success of numerical relativity in successfully simulating the merger phase of Binary Black Hole (BBH) coalescence. The aim of the Numerical INjection Analysis (NINJA) project is to study the sensitivity of gravitational-wave analysis pipelines to numerical simulations of waveforms and foster close collaboration between numerical relativists and data analysts.  NINJA-1 was a huge...
May
25
2011
This workshop brings together researchers with an interest in soft materials, fluids, and biophysics to discuss their work and explore partnerships. All participants may present a sound bite (a few minutes).  The day will include breakfast, lunch, and coffee. Registration is free, but required. Invited Speakers include M. Cristina Marchetti (Keynote Speaker, Syracuse University), Paul Goldbart (Georgia Tech), Juana Mendenhall (Morehouse College), Elisa Riedo (Georgia Tech), Susanne Ullrich (University of Georgia). Location: Georgia Tech, Marcus Nanotechnology Building, Room 1116Registration...
May
24
2011
Obtaining a priori information on strongly interacting many-fermion systems remains a challenging problem in theoretical physics. A promising way forward is the use of Monte Carlo simulations, which are non-perturbative and take full account of quantum fluctuations. A famous example is Lattice QCD, which aims to elucidate the interactions between quarks and gluons at low energies, where QCD is strongly coupled. I will provide an updateon the application of such methods to closely related problems in condensed matter and atomic physics, highlighting modern computational and algorithmic developments. Specific examples include graphene and strongly coupled ultracold Fermi gases.
May
19
2011
Some years ago an anomaly was noted in the decay of luminescence in certain doped alkali halides. The anomaly was eventually explained using a factor of a billion slowdown in lattice relaxation, a remarkable stretching of time scales. This slowdown was found to be caused by the creation of a ‘breather’ in the neighborhood of the dopant. Discrete breathers are nondispersive classical excitations that are known to be significant in many natural systems. In the talk I focus on the occurrence of breathers in doped alkali halides. Several more general properties of breathers have arisen from this study, among them is the quantum breather...
Apr
21
2011
In theory, quantum computers can solve certain problems much more efficiently than classical computers. This possibility has motivated experimental efforts to construct devices that manipulate quantum bits (qubits) in a variety of physical systems. One such system is composed of atomic ions confined by electric fields in a rf Paul trap. The motions of such ions can be modeled to a very good approximation as harmonic oscillators, and with suitable laser cooling techniques they can be cooled to the harmonic oscillator ground state. When trapped within the same potential minimum, ions interact strongly via the Coulomb force, thereby enabling multiple-qubit quantum gates that are...
Apr
20
2011
Yves Couder and coworkers have recently reported the results of a startling series of experiments in which droplets bouncing on a fluid surface exhibit wave-particle duality and, as a consequence, several dynamical features previously thought to be peculiar to the microscopic realm, including single-particle diffraction, interference, tunneling and quantized orbits. We explore this fluid system in light of the Madelung transformation, whereby Schrodinger's equation is recast in a hydrodynamic form. Doing so reveals a remarkable correspondence between bouncing droplets and subatomic particles, and provides rationale for the observed macroscopic quantum behaviour. New experiments are...
Apr
19
2011
I briefly review the formation of color superconductivity which happens in compact stars. Below the temperature scale set by the gap in the quark spectrum, transport properties are determined by collective modes. We compute the thermal conductivity, $\kappa$, of color-flavor locked (CFL) quark matter in the frame of kinetics theory. We present and compare the result with previous estimates. We also conclude a CFL quark matter core ofthe compact star becomes isothermal on a timescale of a few seconds.  Moreover, we compute the thermal conductivity and sound attenuation length of a dilute Fermi gas, which help us comment on the possibility of extracting the shear viscosity of...
Apr
12
2011
In this talk we will discuss a relaxation of high-energy quasiparticles in a weakly interacting one-dimensional Bose liquid. Unlike in higher dimensions, the rate is a nonmonotonic function of temperature. Moreover, it turns out that the inelastic scattering due to deviations from the integrability occurs at a much higher rate than three-body recombination processes, which is the main mechanism of losses in cold-atom-based realizations of 1D Bose liquids.

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