Particle theory

Abstract:

Using gauge theory/gravity duality we study sound wave propagation in strongly coupled non-conformal gauge theory plasma. We compute the speed of sound and the bulk viscosity of N = 2* supersymmetric SU(Nc) Yang-Mills plasma at a temperature much larger than the mass scale of the theory in the limit of large Nc and large 't Hooft coupling. The speed of sound is computed both from the equation of state and the hydrodynamic pole in the stress-energy tensor two-point correlation function. Both computations lead to the same result. Bulk viscosity is determined by computing the attenuation constant of the sound wave mode. © 2005 Elsevier B.V. All rights reserved.

Abstract:

The first sensors of the IceCube neutrino observatory were deployed at the South Pole during the austral summer of 2004-2005 and have been producing data since February 2005. One string of 60 sensors buried in the ice and a surface array of eight ice Cherenkov tanks took data until December 2005 when deployment of the next set of strings and tanks began. We have analyzed these data, demonstrating that the performance of the system meets or exceeds design requirements. Times are determined across the whole array to a relative precision of better than 3 ns, allowing reconstruction of muon tracks and light bursts in the ice, of air-showers in the surface array and of events seen in coincidence by surface and deep-ice detectors separated by up to 2.5 km. © 2006 Elsevier B.V. All rights reserved.

Abstract:

We investigate on the lattice the metastable confined phase above Tc in SU(N) gauge theories, for N=8,10, and 12. In particular we focus on the decrease with the temperature of the mass of the lightest state that couples to Polyakov loops. We find that at T=Tc the corresponding effective string tension σeff(T) is approximately half its value at T=0, and that as we increase T beyond Tc, while remaining in the confined phase, σeff(T) continues to decrease. We extrapolate σeff(T) to even higher temperatures, and interpret the temperature where it vanishes as the Hagedorn temperature TH. For SU(12) we find that TH/Tc=1.116(9), when we use the exponent of the three-dimensional XY model for the extrapolation, which seems to be slightly preferred over a mean-field exponent by our data. © 2006 The American Physical Society.