Abstract:
We show that the shear viscosity of lambda phi^4 theory is sensitive at next-to-leading order to soft physics, which gives rise to subleading corrections suppressed by only a half power of the coupling, eta = [3033.54 + 1548.3 m_{th}/T] N T^3]/[ (N+2)/3 lambda^2], with m^2_th=(N+2)/72 lambda T^2. The series appears to converge about as well (or badly) as the series for the pressure.

Abstract:
We investigate analytically the fermionic fluctuation determinant at finite temperatures in the minimal standard model, including all operators up to dimension 6 and all contributions to the effective potential to all orders in the high $T$ expansion, to 1 loop. We apply the results to find corrections to the Sphaleron erasure rate in the broken phase. We conclude that the analytic treatment of fermions is very reliable and that there is a great deal of baryon erasure after the phase transition for any physical Higgs mass.

Abstract:
I investigate the evolution of finite temperature, classical Yang-Mills field equations under the influence of a chemical potential for Chern Simons number $N_{CS}$. The rate of $N_{CS}$ diffusion, $\Gamma_d$, and the linear response of $N_{CS}$ to a chemical potential, $\Gamma_\mu$, are both computed; the relation $\Gamma_d = 2 \Gamma_\mu$ is satisfied numerically and the results agree with the recent measurement of $\Gamma_d$ by Ambjorn and Krasnitz. The response of $N_{CS}$ under chemical potential remains linear at least to $\mu = 6 T$, which is impossible if there is a free energy barrier to the motion of $N_{CS}$. The possibility that the result depends on lattice artefacts via hard thermal loops is investigated by changing the lattice action and by examining elongated rectangular lattices; provided that the lattice is fine enough, the result is weakly if at all dependent on the specifics of the cutoff. I also compare SU(2) with SU(3) and find $\Gamma_{\rm SU(3)} \sim 7 (\alpha_s/\alpha_w)^4 \Gamma_{\rm SU(2)}$.

Abstract:
We show how to make O(a) corrections in the bare parameters of 3-D lattice SU(2) times U(1) Higgs theory which remove O(a) errors in the match between the infrared behavior and the infrared behavior of the continuum theory. The corrections substantially improve the convergence of lattice data to a small a limit.

Abstract:
We compute the matching conditions between lattice and continuum 3-D SU(N) Higgs theories, with both adjoint and fundamental scalars, at O(a), except for additive corrections to masses and Higgs field operator insertions.

Abstract:
Bodeker has recently shown that the high temperature sphaleron rate, which measures baryon number violation in the hot standard model, receives logarithmic corrections to its leading parametric behavior; Gamma = kappa' [log(m_D / g^2 T) + O(1)] (g^2 T^2 / m_D^2) \alpha_W^5 T^4. After discussing the physical origin of these corrections, I compute the leading log coefficient numerically; kappa' = 10.8 pm 0.7. The log is fairly small relative to the O(1) ``correction;'' so nonlogarithmic contributions dominate at realistic values of the coupling.

Abstract:
I develop an improved Hamiltonian for classical, Minkowski Yang-Mills theory, which evolves infrared fields with corrections from lattice spacing $a$ beginning at $O(a^4)$. I use it to investigate the response of Chern-Simons number to a chemical potential, and to compute the maximal Lyapunov exponent. Both quantities have small $a$ limits, in both cases within $10\% $ of the limit found using the unimproved (Kogut Susskind) Hamiltonian. For the maximal Lyapunov exponent the limits differ by about $5 \% $, significant at about $5 \sigma$, indicating that while a small $a$ limit exists, its value is corrupted by lattice artefacts. For the response of Chern-Simons number the statistics are not good enough to resolve $ 5 \% $ differences, but it seems possible in analogy with the Lyapunov exponent that the final answer depends on the lattice regulation.

Abstract:
I present a technique for measuring the broken phase sphaleron rate nonperturbatively. There are three parts to the calculation: determination of the probability distribution of Chern-Simons number NCS; measurement of <| d\NCS/dt |> at NCS=1/2, the mean rate of change of NCS at the barrier; and measurement of the ``dynamical prefactor,'' the fraction of barrier crossings which result in a permanent integer change in NCS.

Abstract:
Recently Bodeker has presented an effective infrared theory for the dynamics of Yang-Mills theory, suitable for studying the rate of baryon number violation in the early universe. We extend his theory to include Higgs fields, and study how much the Higgs affects the baryon number violation rate in the symmetric phase, at the phase coexistence temperature of a first order electroweak phase transition. The rate is about 20% smaller than in pure Yang-Mills theory. We also analyze the sphaleron rate in the analytic crossover regime. Our treatment relies on the ergodicity conjecture for 3-D scalar $\phi^4$ theory.

Abstract:
We present an entirely analytic, leading log order determination of the friction an electroweak bubble wall feels during a first order electroweak phase transition. The friction is dominated by W bosons, and gives a wall velocity parametrically ~ alpha_w, and numerically small, ~ .01 -- 0.1 depending on the Higgs mass.