Effective Scalar Field Theory for the Electroweak Phase Transition

We investigate an effective model for the finite temperature restoration phase transition of the electroweak theory. It is obtained by dimensional reduction of the $3+1$ dimensional full theory and by subsequent integration over all static gauge degrees of freedom. The resulting theory corresponds to a $3$-dimensional $O(4)$ ferromagnet containing cubic and quartic terms of the field in its potential function. Possible nonperturbative effects of a magnetic screening mass are parametrically included in the potential. We analyse the theory using mean field and numerical Monte Carlo (MC) simulation methods. At the value of the physical Higgs mass, $m_H=37~{\rm GeV}$, considered in the present investigation, we find a discontinuous symmetry restoring phase transition. We determine the critical temperature, order parameter jump, interface tension and latent heat characteristics of the transition. The Monte Carlo results indicate a somewhat weaker first order phase transition as compared to the mean field treatment, demonstrating that non-perturbative fluctuations of the Higgs field are relevant. This effect is especially important for the interface tension. Any observation of hard first order transition could result only from non-perturbative effects related to the gauge degrees of freedom.Comment: 28 pages and 18 figure

Interface Tension of the Electroweak Phase Transition

In our nonperturbative lattice investigation we study the interface tension of the finite-temperature electroweak phase transition. In this analysis the Higgs mass has been chosen to be about $35$ GeV. At the transition point of a finite volume system, tunnelling between the symmetric and the Higgs phase takes place. This phenomenon leads to a splitting of the ground state, which can be used to determine the interface tension. The result obtained this way agrees with the result of the two-coupling method and with the prediction of the perturbative approach.Comment: 10 pages, five figures in uuencoded PS format, Latex + epsf.st

Transition temperature of a dilute homogeneous imperfect Bose gas

The leading-order effect of interactions on a homogeneous Bose gas is theoretically predicted to shift the critical temperature by an amount \Delta\Tc = # a_{scatt} n^{1/3} T_0 from the ideal gas result T_0, where a_{scatt} is the scattering length and n is the density. There have been several different theoretical estimates for the numerical coefficient #. We claim to settle the issue by measuring the numerical coefficient in a lattice simulation of O(2) phi^4 field theory in three dimensions---an effective theory which, as observed previously in the literature, can be systematically matched to the dilute Bose gas problem to reproduce non-universal quantities such as the critical temperature. We find # = 1.32 +- 0.02.Comment: 4 pages, submitted to Phys. Rev. Lett; minor changes due to improvement of analysis in the longer companion pape

Finite T Electroweak Phase Transition on the Lattice

This talk reviews recent lattice results on the high $T$ electroweak phase transition. A remarkably accurate picture emerges: a) the transition is of first order for m_H \lsim 80GeV and vanishes for larger $m_H$; b) transition temperature, latent heat and interface tension are known, as well as c) the properties of the broken and symmetric phases. New developments in the sphaleron rate calculations are discussed.Comment: Talk presented at LATTICE96(electroweak), 13 pages latex, 11 eps-figure

Radiatively-Induced First-Order Phase Transitions: The Necessity of the Renormalization Group

We advocate a (Wilson) renormalization-group (RG) treatment of finite-temperature first-order phase transitions, in particular those driven by radiative corrections such as occur in the standard model, and other spontaneously-broken gauge theories. We introduce the scale-dependent coarse-grained free energy S_\La[\phi] which we explicitly calculate, using the Wilson RG and a (4-\ep)-expansion, for a scalar toy model that shares many features of the gauged case. As argued by Langer and others, the dynamics of the phase transition are described by S_\La[\phi] with \La of order the bubble wall thickness, and {\it not} by the usual (RG-improved) finite-temperature effective action which is reproduced by S_\La[\phi] for \La\to 0. We argue that for weakly first-order transitions (such as that in the standard model) the (4-\ep)-expansion is necessary to control an inevitable growth of the effective scale-dependent coupling towards the strong-coupling regime, and that diagrammatic resummation techniques are unlikely to be appropriate.Comment: 26 pages, two figures, LaTex macropackage. References added and appendix A revised. LBL preprint LBL-3457

Hot electroweak matter

This talk summarises recent results on lattice Monte Carlo studies of finite T electroweak phase transition. Particular attention is given to the 3d effective theory approach, replacing the full 4d theory by a three dimensional effective theory of the modes constant in imaginary time.Comment: 10 pages, uuencoded compressed postscript file, contribution to LATTICE9

A Non-Perturbative Analysis of the Finite T Phase Transition in SU(2)xU(1) Electroweak Theory

The continuum 3d SU(2)$\times$U(1)+Higgs theory is an effective theory for a large class of 4d high-temperature gauge theories, including the minimal standard model and some of its supersymmetric extensions. We study the effects of the U(1) subgroup using lattice Monte Carlo techniques. When $g'^2/g^2$ is increased from the zero corresponding to pure SU(2)+Higgs theory, the phase transition gets stronger. However, the increase in the strength is close to what is expected perturbatively, and the qualitative features of the phase diagram remain the same as for $g'^2=0$. In particular, the first order transition still disappears for $m_H>m_{H,c}$. We measure the photon mass and mixing angle, and find that the mass vanishes in both phases within the statistical errors.Comment: Latex, 30 pages, 15 eps figure

Establishing Telepathology in Africa: Lessons From Botswana

Few reports of telepathology in Africa exist in the medical literature. With the strong need for improvement in health care infrastructure and personnel training in many African nations, telepathology provides a rapid and versatile tool to improve clinical care and foster educational and research opportunities. We describe the challenges faced in establishing robotic telepathology (RT) services at a government referral center in Botswana and reflect on conditions under which such initiatives may be most likely to succeed in sub-Saharan Africa and other parts of the developing world