The infrared properties of the high-temperature limit of Landau-gauge Yang-Mills theory are investigated. In a first step the high-temperature limit of the Dyson-Schwinger equations is taken. The resulting equations are identical to the Dyson-Schwinger equations of the dimensionally reduced theory, a three-dimensional Yang-Mills theory coupled to an effective adjoint Higgs field. These equation...

We derive the low-energy effective field theory at finite temperature of Bose condensed liquids (e.g., superfluid 4He) directly from the breakdown of the global gauge symmetry U(1). The theory can immediately yield the Landau quantum hydrodynamics. The Bogoliubov type spectrum of low-energy collective excitations is given in the zeroth order of this theory and the momentum and temperature depen...

The AdS/CFT correspondence provides valuable constraints on the possible exact form of various physical quantities in the N = 4 super Yang-Mills theory in the large N limit. We examine the free energy as the expansions in a small as well as in a large ’t Hooft parameter λ. We argue that it is impossible to smoothly extrapolate from the weak coupling regime to the strong coupling regime, thus th...

An optimized perturbation theory (OPT) at finite temperature T , which resums higher order terms in the naive perturbation, is developed in O(N) φ theory. It is proved that (i) the renormalization of the ultra-violet divergences can be carried out systematically in any given order of OPT, and (ii) the Nambu-Goldstone theorem is fulfilled for arbitrary N and for any given order of OPT. The metho...

The interaction between static D0-branes at finite temperature is considered in the matrix theory and the superstring theory. The results agree in both cases to the leading order in the supersymmetry violation by temperature, where the one-loop approximation is reliable. The effective static potential is short-ranged and attractive. Talk at the 32nd International Symposium Ahrenshoop on the The...

We study QCD with two flavours of colour-sextet quarks as a candidate walking-Technicolor theory. We simulate lattice QCD with two flavours of colour-sextet staggered quarks at finite temperatures to observe the scales of confinement and chiral-symmetry breaking. These should give us some indication as to whether the massless theory has an infrared fixed point making it a conformal field theory...