The endpoint of the electroweak phase transition

The 3d SU(2)-Higgs model is used to find the critical Higgs mass above which the first order phase transition ends. One method is focused on the disappearance of the two-state signal of the scalar condensate (vanishing of the latent heat). Another method is based on the analysis of Lee-Yang zeroes of the partition function which allows to characterise the change from first order transition into an analytical crossover.Comment: 3 pages, 5 figures, uses espcrc2.sty, contribution to LATTICE9

Hot electroweak matter near to the endpoint of the phase transition

The electroweak phase transition is investigated near to its endpoint in the framework of an effective three-dimensional model. We measure the very weak interface tension with the tunneling correlation length method. First results for the mass spectrum and the corresponding wave functions in the symmetric phase are presented.Comment: 3 pages, 5 figures, uses espcrc2.sty, contribution to LATTICE9

Scalar-gauge dynamics in (2+1) dimensions at small and large scalar couplings

We present the results of a detailed calculation of the excitation spectrum of states with quantum numbers J^{PC}=0++, 1-- and 2++ in the three-dimensional SU(2) Higgs model at two values of the scalar self-coupling and for fixed gauge coupling. In the context of studies of the electroweak phase transition at finite temperature these couplings correpond to tree-level, zero temperature Higgs masses of 35 GeV and 120 GeV, respectively. We also study the properties of Polyakov loop operators, which serve to test the confining properties of the model in the symmetric phase. At both values of the scalar coupling we obtain masses of bound states consisting entirely of gauge degrees of freedom ("W-balls"), which are very close to those obtained in the pure gauge theory. We conclude that the previously observed, approximate decoupling of the scalar and gauge sectors of the theory persists at large scalar couplings. We study the crossover region at large scalar coupling and present a scenario how the confining properties of the model in the symmetric phase are lost inside the crossover by means of flux tube decay. We conclude that the underlying dynamics responsible for the observed dense spectrum of states in the Higgs region at large couplings must be different from that in the symmetric phase.Comment: 36 pages, LaTeX, 13 postscript files, to be included with epsf; improved presentation, updated references, conclusions unchanged; version to appear in Nucl. Phys.

Vortex profiles and vortex interactions at the electroweak crossover

Local correlations of Z-vortex operators with gauge and Higgs fields (lattice quantum vortex profiles) as well as vortex two-point functions are studied in the crossover region near a Higgs mass of 100 GeV within the 3D SU(2) Higgs model. The vortex profiles resemble certain features of the classical vortex solutions in the continuum. The vortex-vortex interactions are analogous to the interactions of Abrikosov vortices in a type-I superconductor.Comment: talk at LATTICE99(electroweak), 3 pages and 5 EPS figure

Constrained fitting of three-point functions

We determine matrix elements for $B \to D$ semileptonic decay. The use of the constrained fitting method and multiple smearings for both two- and three-point correlators allows an improved calculation of the form factors.Comment: Talk given at Lattice2001(heavyquark), 3 pages, 4 figure

The Ising model universality of the electroweak theory

Lattice simulations have shown that the first order electroweak phase transition turns into a regular cross-over at a critical Higgs mass m_{H,c}. We have developed a method which enables us to make a detailed investigation of the critical properties of the electroweak theory at m_{H,c}. We find that the transition falls into the 3d Ising universality class. The continuum limit extrapolation of the critical Higgs mass is m_{H,c} = 72(2) GeV, which implies that there is no electroweak phase transition in the Standard Model.Comment: 3 pages, contribution to LATTICE98(electroweak

Non-perturbative renormalisation for overlap fermions

Using non-perturbative techniques we have found the renormalisation factor, Z, in the RI-MOM scheme for quark bilinear operators in quenched QCD. We worked with overlap fermions using the Luescher-Weisz gauge action. Our calculation was performed at beta=8.45 at a lattice spacing of 1/a=2.1 GeV using a value of rho=1.4. Our results show good agreement between the vector and the axial vector in the zero mass limit. This shows that overlap fermions have good chiral properties. To attempt to improve the discretisation errors in our results we subtracted the O(a^2) terms in one-loop lattice perturbation theory from the Monte Carlo Green functions. In particular we paid attention to the operators for the observable . We found a value for the renormalisation constants Z^msbar_(v_2b) and Z^msbar_(v_2a) just less than 1.9 at mu=1/a=2.1 GeV.Comment: 6 pages, 3 figures, uses PoS style, poster presented at Lattice 2005 (Chiral Fermions), to be published in Proceedings of Scienc

Detailed Phase Transition Study at M_H <= 70 GeV in a 3-dimensional SU(2)SU(2)--Higgs Model

We study the electroweak phase transition in an effective 3-dimensional theory for a Higgs mass of about 70 GeV by Monte Carlo simulations. The transition temperature and jumps of order parameters are obtained and extrapolated to the continuum using multi-histogram techniques and finite size analysis.Comment: Talk presented at LATTICE96(electroweak), 4 pages, 5 figure

Lattice-continuum relations for 3d SU(N)+Higgs theories

3d lattice studies have recently attracted a lot of attention, especially in connection with finite temperature field theories. One ingredient in these studies is a perturbative computation of the 2-loop lattice counterterms, which are exact in the continuum limit. We extend previous such results to SU(N) gauge theories with Higgs fields in the fundamental and adjoint representations. The fundamental SU(3)xSU(2) case might be relevant for the electroweak phase transition in the MSSM, and the adjoint case for the GUT phase transition and for QCD in the high temperature phase. We also revisit the standard SU(2)xU(1) and U(1) theories.Comment: 21 page