Photon and electron spectra in hot and dense QED

Photon and electron spectra in hot and dense QED are found in the high temperature limit for all |\q| using the Feynman gauge and the one-loop self-energy. All spectra are split by the medium and their branches develop the gap (the dynamical mass) at zero momentum. The photon spectrum has two branches (longitudinal and transverse) with the common mass; but electron spectrum is split on four branches which are well-separated for any |\q| including their |\q|=0 limits (their effective masses). These masses and the photon thermal mass are calculated explicitly and the different limits of spectrum branches are established in detail. The gauge invariance of the high-temperature spectra is briefly discussed.Comment: 9 pages, latex, no figure

Soliton absorption spectroscopy

We analyze optical soliton propagation in the presence of weak absorption lines with much narrower linewidths as compared to the soliton spectrum width using the novel perturbation analysis technique based on an integral representation in the spectral domain. The stable soliton acquires spectral modulation that follows the associated index of refraction of the absorber. The model can be applied to ordinary soliton propagation and to an absorber inside a passively modelocked laser. In the latter case, a comparison with water vapor absorption in a femtosecond Cr:ZnSe laser yields a very good agreement with experiment. Compared to the conventional absorption measurement in a cell of the same length, the signal is increased by an order of magnitude. The obtained analytical expressions allow further improving of the sensitivity and spectroscopic accuracy making the soliton absorption spectroscopy a promising novel measurement technique.Comment: 9 pages, 7 figures

Ultrasoft Quark Damping in Hot QCD

We determine the quark damping rates in the context of next-to-leading order hard-thermal-loop summed perturbation of high-temperature QCD where weak coupling is assumed. The quarks are ultrasoft. Three types of divergent behavior are encountered: infrared, light-cone and at specific points determined by the gluon energies. The infrared divergence persists and is logarithmic whereas the two others are circumvented.Comment: 16 page

Infrared Behavior of High-Temperature QCD

The damping rate \gamma_t(p) of on-shell transverse gluons with ultrasoft momentum p is calculated in the context of next-to-leading-order hard-thermal-loop-summed perturbation of high-temperature QCD. It is obtained in an expansion to second order in p. The first coefficient is recovered but that of order p^2 is found divergent in the infrared. Divergences from light-like momenta do also occur but are circumvented. Our result and method are critically discussed, particularly regarding a Ward identity obtained in the literature. When enforcing the equality between \gamma_t(0) and \gamma_l(0), a rough estimate of the magnetic mass is obtained. Carrying a similar calculation in the context of scalar quantum electrodynamics shows that the early ultrasoft-momentum expansion we make has little to do with the infrared sensitivity of the result.Comment: REVTEX4, 55 page

Invariant measure in hot gauge theories

We investigate properties of the invariant measure for the $A_0$ gauge field in finite temperature gauge theories both on the lattice and in the continuum theory. We have found the cancellation of the naive measure in both cases. The result is quite general and holds at any finite temperature. We demonstrate, however, that there is no cancellation at any temperature for the invariant measure contribution understood as Z(N) symmetrical distribution of gauge field configurations. The spontaneous breakdown of Z(N) global symmetry is entirely due to the potential energy term of the gluonic interaction in the effective potential. The effects of this measure on the effective action, mechanism of confinement and $A_0$ condensation are discussed.Comment: Latex file, 65.5kB, no figure

Non-Abelian Collective Excitations in Unlinearized Quark-Gluon Plasma Media

We study the effect of unlinearized medium on the collective excitations in quark-gluon plasma. We present two kinds of non-Abelian oscillation solutions which respectively correspond to weakly and strongly nonlinear coupling of field components in color space. We also show that the weakly nonlinear solution is similar to Abelian-like one but has the frequency shift, which is of order $g^2T$, from eigenfrequency.Comment: 7 page

How fast can the wall move? A study of the electroweak phase transition dynamics

We consider the dynamics of bubble growth in the Minimal Standard Model at the electroweak phase transition and determine the shape and the velocity of the phase boundary, or bubble wall. We show that in the semi-classical approximation the friction on the wall arises from the deviation of massive particle populations from thermal equilibrium. We treat these with Boltzmann equations in a fluid approximation. This approximation is reasonable for the top quarks and the light species while it underestimates the friction from the infrared $W$ bosons and Higgs particles. We use the two-loop finite temperature effective potential and find a subsonic bubble wall for the whole range of Higgs masses $0<m_H<90$GeV. The result is weakly dependent on $m_H$: the wall velocity $v_w$ falls in the range $0.36<v_w<0.44$, while the wall thickness is in the range $29> L T > 23$. The wall is thicker than the phase equilibrium value because out of equilibrium particles exert more friction on the back than on the base of a moving wall. We also consider the effect of an infrared gauge condensate which may exist in the symmetric phase; modelling it simplemindedly, we find that the wall may become supersonic, but not ultrarelativistic.Comment: 42 pages, plain latex, with three figures. Minor editing August 1 (we figured out how to do analytically some integrals we previously did numerically, made corresponding (slight) changes to numerical results, and corrected some typos.

Advances in perturbative thermal field theory

The progress of the last decade in perturbative quantum field theory at high temperature and density made possible by the use of effective field theories and hard-thermal/dense-loop resummations in ultrarelativistic gauge theories is reviewed. The relevant methods are discussed in field theoretical models from simple scalar theories to non-Abelian gauge theories including gravity. In the simpler models, the aim is to give a pedagogical account of some of the relevant problems and their resolution, while in the more complicated but also more interesting models such as quantum chromodynamics, a summary of the results obtained so far are given together with references to a few most recent developments and open problems.Comment: 84 pages, 18 figues, review article submitted to Reports on Progress in Physics; v2, v3: minor additions and corrections, more reference

Phase of the Wilson Line at High Temperature in the Standard Model

We compute the effective potential for the phase of the Wilson line at high temperature in the standard model to one loop order. Besides the trivial vacua, there are metastable states in the direction of $U(1)$ hypercharge. Assuming that the universe starts out in such a metastable state at the Planck scale, it easily persists to the time of the electroweak phase transition, which then proceeds by an unusual mechanism. All remnants of the metastable state evaporate about the time of the $QCD$ phase transition.Comment: 4 pages in ReVTeX plus 1 figure; Columbia Univ. preprint CU-TP-63