Prethermalisation and the Build Up of the Higgs Effect

Real time field excitations in the broken symmetry phase of the classical abelian Gauge+Higgs model are studied numerically in the unitary gauge, for systems starting from the unstable maximum of the Higgs potential.Comment: 5 pages, 6 figures, to appear in proceedings of SEWM'0

Spontaneously broken ground states of the U(n)_L x U(n)_R linear sigma model at large n

Symmetry breaking patterns of the U(n)_L x U(n)_R symmetric meson model are investigated in a formulation involving three auxiliary composite fields. The effective potential is constructed at leading order in the 1/n expansion for a condensate belonging to the center of the U(n) group. A wide region is found in the coupling space where in addition to the condensate proportional to the unit matrix, also metastable minima exist, in which a further breakdown of the diagonal U_V(n) symmetry to U_V(n-1) is realized. Application of a moderate external field conjugate to this component of the order parameter changes this state into the true ground state of the system.Comment: ReVTeX4, 10 pages, 5 figures. Extended introduction and conclusion. Version published in Phys. Rev.

Beyond HTL: The Classical Kinetic Theory of Landau Damping for Selfinteracting Scalar Fields in the Broken Phase

The effective theory of low frequency fluctuations of selfinteracting scalar fields is constructed in the broken symmetry phase. The theory resulting from integrating fluctuations with frequencies much above the spontanously generated mass scale $(p_0>>M)$ is found to be local. Non-local dynamics, especially Landau damping emerges under the effect of fluctuations in the $p_0 \sim M$ region. A kinetic theory of relativistic scalar gas particles interacting via their locally variable mass with the low frequency scalar field is shown to be equivalent to this effective field theory for scales below the characteristic mass, that is beyond the accuracy of the Hard Thermal Loop (HTL) approximation.Comment: 5 pages, Latex, uses sprocl.sty, to be published in the Proceedings of SEWM 98 Conference Copenhagen, Denmark 2-5 December 199

Non-Gaussian fixed points in fermionic field theories without auxiliary Bose-fields

The functional equation governing the renormalization flow of fermionic field theories is investigated in $d$ dimensions without introducing auxiliary Bose-fields on the example of the Gross-Neveu and the Nambu--Jona-Lasinio model. The UV safe fixed points and the eigenvectors of the renormalization group equations linearized around them are found in the local potential approximation. The results are compared carefully with those obtained with partial bosonisation. The results do not receive any correction in the next-to-leading order approximation of the gradient expansion of the effective action.Comment: extended version to appear in EPJC, 15 pages, 4 figures, uses svjour

Effect of the scalar condensate on the linear gauge field response in the Abelian Higgs model

The effective equations of motion for low-frequency mean gauge fields in the Abelian Higgs model are investigated in the presence of a scalar condensate, near the high temperature equilibrium. We determine the current induced by an inhomogeneous background gauge field in the linear response approximation up to order $e^4$, assuming adiabatic variation of the scalar fields. The physical degrees of freedom are found and a physical gauge choice for the numerical study of the combined Higgs+gauge evolution is proposed.Comment: 11 pages, latex, no figure

Surface energy from order parameter profile: At the QCD phase transition

The order parameter profile between coexisting confined and plasma regions at the quantum chromodynamic (QCD) phase transition is constructed. The dimensionless combination of the surface energy (Sigma) and the correlation length (Zeta) is estimated to be Sigma Zeta 3 approximately equals 0.8