arXiv subjects
Publications and source records attributed to Guy D. Moore.
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.
We construct an extension of the standard Kogut-Susskind lattice model for classical 3+1 dimensional Yang-Mills theory, in which ``classical particle'' degrees of freedom are added. We argue that this will correctly reproduce the ``hard thermal loop'' effects of hard degrees of freedom, while giving a local implementation which is numerically tractable. We prove that the extended system is Hamiltonian and has the same thermodynamics as dimensionally reduced hot Yang-Mills theory put on a lattice. We present a numerical update algorithm and study the abelian theory to verify that the classical gauge theory self-energy is correctly modified. Then we use the extended system to study the diffusion constant for Chern-Simons number. We verify the Arnold-Son-Yaffe picture that the diffusion constant is inversely proportional to hard thermal loop strength. Our numbers correspond to a diffusion constant of Gamma = 29 +- 6 alpha_w^5 T^4 for m_D^2 = 11 g^2 T^2/6.
We develop a topological method of measuring Chern-Simons number change in the real time evolution of classical lattice SU(2) and SU(2) Higgs theory. We find that the Chern-Simons number diffusion rate per physical 4-volume is very heavily suppressed in the broken phase, and that it decreases with lattice spacing in pure Yang-Mills theory, although not as quickly as predicted by Arnold, Son, and Yaffe.
We measure the diffusion constant for Chern-Simons number for classical, lattice SU(3) Yang-Mills theory, using a generalization of the topological definition of Chern-Simons number developed recently by Moore and Turok. The diffusion constant is much larger than that for SU(2), even before the ratio of coupling constants has been accounted for, which implies that chiral quark number is efficiently destroyed by strong processes during the electroweak phase transition. For the physical value of α_s we estimate the decay time for chiral quark number to be about 80/T, although various systematics make this number uncertain by about a factor of 2.
I discuss the applicability of classical techniques to the study of the dynamics of infrared, bosonic fields at the electroweak phase transition. I present the lattice as a natural means of cutting off hard, nonclassical modes, and discuss the problem of integrating out the excluded modes perturbatively. I then apply the classical lattice technique to study the dynamics of the phase interface (bubble wall) and the generation of Chern-Simons number in each phase and on the bubble wall.
We investigate the thermodynamics and dynamics of the electroweak phase transition by modelling the infrared physics with classical Yang-Mills Higgs theory. We discuss the accuracy of this approach and conclude that, for quantities whose determination is dominated by the infrared, the classical method should be correct up to parametrically suppressed (ie O(alpha)) corrections. For a Higgs self-coupling which at tree level corresponds to m_H ~ 50 GeV, we determine the jump in the order parameter to be delta phi = 1.5 gT, the surface tension to be sigma = 0.07 g^4 T^3, and the friction coefficient on the moving bubble wall due to infrared bosons to be η= P/v_w = 0.03 \pm .004 g^6 T^4. We also investigate the response of Chern-Simons number to a spatially uniform chemical potential and find that it falls off a short distance inside the bubble wall, both in equilibrium and below the equilibrium temperature.
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.
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, $Γ_d$, and the linear response of $N_{CS}$ to a chemical potential, $Γ_μ$, are both computed; the relation $Γ_d = 2 Γ_μ$ is satisfied numerically and the results agree with the recent measurement of $Γ_d$ by Ambjorn and Krasnitz. The response of $N_{CS}$ under chemical potential remains linear at least to $μ= 6 T$, 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 $Γ_{\rm SU(3)} \sim 7 (α_s/α_w)^4 Γ_{\rm SU(2)}$.
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 $5 σ$, 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.
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.
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 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.
We calculate the velocity and thickness of a bubble wall at the electroweak phase transition in the Minimal Standard Model. We model the wall with semiclassical equations of motion and show that friction arises from the deviation of massive particle populations from thermal equilibrium. We treat these with Boltzmann equations in a fluid approximation in the background of the wall. Our analysis improves on the previous work by using the two loop effective potential, accounting for particle transport, and determining the wall thickness dynamically. We find that the wall is significantly thicker than at phase equilibrium, and that the velocity is fairly high, $v_w \simeq 0.7c$, and quite weakly dependent on the Higgs mass.