Particle theory

Abstract:

As a non-trivial check of the non-supersymmetric gauge/gravity duality, we use a near-extremal black brane background to compute the retarded Green's functions of the stress-energy tensor in N = 4 super-Yang-Mills (SYM) theory at finite temperature. For the long-distance, low-frequency modes of the diagonal components of the stress-energy tensor, hydrodynamics predicts the existence of a pole in the correlators corresponding to propagation of sound waves in the N = 4 SYM plasma. The retarded Green's functions obtained from gravity do indeed exhibit this pole, with the correct values for the sound speed and the rate of attenuation. © SISSA/ISAS 2003.

Abstract:

We consider a class of multi-matrix models with an action which is O(D) invariant, where D is the number of NxN Hermitian matrices X_\mu, \mu=1,...,D. The action is a function of all the elementary symmetric functions of the matrix $T_{\mu\nu}=Tr(X_\mu X_\nu)/N$. We address the issue whether the O(D) symmetry is spontaneously broken when the size N of the matrices goes to infinity. The phase diagram in the space of the parameters of the model reveals the existence of a critical boundary where the O(D) symmetry is maximally broken.

Abstract:

We investigate the properties of the deconfinement transition in SU(4) and SU(6) gauge theories. We find that it is a 'normal' first order transition in both cases, from which we conclude that the transition is first order in the N → ∞ limit. Comparing our preliminary estimates of the continuum values of Tc/√σ with existing values for SU(2) and SU(3) demonstrates a weak dependence on N for all values of N. © 2002 Published by Elsevier Science B.V.