Two-Loop Self-Energy and Multiple Scattering at Finite Temperature

One and two loop self-energies are worked out explicitly for a heavy scalar field interacting weakly with a light self-interacting scalar field at finite temperature. The ring/daisy diagrams and a set of necklace diagrams can be summed simultaneously. This simple model serves to illustrate the connection between multi-loop self-energy diagrams and multiple scattering in a medium.Comment: 15 pages including 7 figures; v2. with appendix added, accepted by PR

Baryonic coherent state formation from small domain disoriented chiral condensates

Rare hyperon yields such as the Omega and AntiOmega in heavy ion collision experiments are hard to be reproduced by numerical models. This, in combination with the thermal fit to SPS data, seems to call for a new production mechanism beyond the usual ones. Small domain disoriented chiral condensates (DCC) were proposed to be such a source of rare hyperons through skyrmion formation at the chiral phase transition. Here skyrmions are treated as coherent states of baryons on a compact manifold so that the distribution of baryons produced from a skyrmion can be known. From this more refined treatment, the number of topological defects produced are more than doubled to 30 or more and the domain size at the SPS is found to be even smaller than before at 1.1--1.5 fm. IT IS IMPERATIVE THEREFORE NOT TO USE ONLY PION DISTRIBUTION BUT OTHER MEANS FOR OBSERVING DCC.Comment: Talk presented at Quark Matter 2002, Nantes, France, July 2002, to appear in the proceeding

Low-Energy Theorems for Gluodynamics at Finite Temperature

We generalize the low-energy theorems of gluodynamics to finite temperature. Examples of the theorems in the low and high temperature limits are given.Comment: 8 pages latex plus 1 postscript figur

Thermal rates for baryon and anti-baryon production

We use a form of the fluctuation-dissipation theorem to derive formulas giving the rate of production of spin-1/2 baryons in terms of the fluctuations of either meson or quark fields. The most general formulas do not assume thermal or chemical equilibrium. When evaluated in a thermal ensemble we find equilibration times on the order of 10 fm/c near the critical temperature in QCD.Comment: 22 pages, 4 tables and 2 figures, REVTe

Critical Points in the QCD Phase Diagram with Two Flavors of Quarks

We employ the linear sigma model to study the chiral dynamics of two flavors of quarks at finite temperature and density. Our calculations include thermal fluctuations of both the bosonic and fermionic fields. In particular, we determine the phase diagram in the plane of temperature and baryon chemical potential as a function of the pion mass. An interesting phase structure occurs that results in zero, one, or two critical points depending on the value of the vacuum pion mass.Comment: 4 pages, Quark Matter 2009 proceeding

Mass shift, width broadening and spectral density of rho-mesons produced in heavy ion collisions

Our recent work on modifications of rho-mesons formed at the last stage of evolution of hadronic matter produced in heavy ion collisions is summarized. It is found that while the mass shift is on the order of a few tens of MeV, the width and spectral density become so broad that rho may lose its identity as a well defined resonance.Comment: Talk given at Quark Matter '99, the 14th International Conference on Ultra-Relativistic Nucleus-Nucleus Collisions, Torino, Italy, May 10-14, 1999. 4 pages, Latex, 4 PS figure

Correct path-integral formulation of quantum thermal field theory in coherent-state representation

The path-integral quantization of thermal scalar, vector and spinor fields is performed newly in the coherent-state representation. In doing this, we choose the thermal electrodynamics and $\phi ^4$ theory as examples. By this quantization, correct expressions of the partition functions and the generating functionals for the quantum thermal electrodynamics and $\phi ^4$ theory are obtained in the coherent-state representation. These expressions allow us to perform analytical calculations of the partition functions and generating functionals and therefore are useful in practical applications. Especially, the perturbative expansions of the generating functionals are derived specifically by virtue of the stationary-phase method. The generating functionals formulated in the position space are re-derived from the ones given in the coherent-state representation

Leptogenesis from Pseudo-Scalar Driven Inflation

We examine recent claims for a considerable amount of leptogenesis, in some inflationary scenarios, through the gravitational anomaly in the lepton number current. We find that when the short distances contributions are properly included the amount of lepton number generated is actually much smaller.Comment: JHEP style, 11 pages. Corrected typ

Nucleation Rate of Hadron Bubbles in Baryon-Free Quark-Gluon Plasma

We evaluate the factor $\kappa$ appearing in Langer's expression for the nucleation rate extended to the case of hadron bubbles forming in zero baryon number cooled quark-gluon plasma. We consider both the absence and presence of viscosity and show that viscous effects introduce only small changes in the value of $\kappa$Comment: 9 pages, revtex, no figures Full postscript version available at via the WWW at http://nucth.physics.wisc.edu/preprints/ or by via from ftp://nucth.physics.wisc.edu/pub/preprints/mad-nt-95-06.p

Perturbative Quantum Field Theory at Positive Temperatures: An Axiomatic Approach

It is shown that the perturbative expansions of the correlation functions of a relativistic quantum field theory at finite temperature are uniquely determined by the equations of motion and standard axiomatic requirements, including the KMS condition. An explicit expression as a sum over generalized Feynman graphs is derived. The canonical formalism is not used, and the derivation proceeds from the beginning in the thermodynamic limit. No doubling of fields is invoked. An unsolved problem concerning existence of these perturbative expressions is pointed out.Comment: 17pages Late