194 research outputs found
Classical Statistical Mechanics and Landau Damping
We study the retarded response function in scalar -theory at finite
temperature. We find that in the high-temperature limit the imaginary part of
the self-energy is given by the classical theory to leading order in the
coupling. In particular the plasmon damping rate is a purely classical effect
to leading order, as shown by Aarts and Smit. The dominant contribution to
Landau damping is given by the propagation of classical fields in a heat bath
of non-interacting fields.Comment: 9 pages, 3 eps figures, LaTe
Gauge Invariant Treatment of the Electroweak Phase Transition
We evaluate the gauge invariant effective potential for the composite field
in the SU(2)-Higgs model at finite temperature.
Symmetric and broken phases correspond to the domains and
, respectively. The effective potential increases very steeply
at small values of . Predictions for several observables, derived from
the ordinary and the gauge invariant effective potential, are compared. Good
agreement is found for the critical temperature and the jump in the order
parameter. The results for the latent heat differ significantly for large Higgs
masses.Comment: 8 pages latex, DESY-94-043, 4 figures can be obtained via e-mail from
[email protected]
Whitening of the Quark-Gluon Plasma
Parton-parton collisions do not neutralize local color charges in the
quark-gluon plasma as they only redistribute the charges among momentum modes.
We discuss color diffusion and color conductivity as the processes responsible
for the neutralization of the plasma. For this purpose, we first compute the
conductivity and diffusion coefficients in the plasma that is significantly
colorful. Then, the time evolution of the color density due to the conductivity
and diffusion is studied. The conductivity is shown to be much more efficient
than the diffusion in neutralizing the plasma at the scale longer than the
screening length. Estimates of the characteristic time scales, which are based
on close to global equilibrium computations, suggest that first the plasma
becomes white and then the momentum degrees of freedom thermalize.Comment: 9 pages, revised, to appear in Phys. Rev.
Chern-Simons Number Diffusion and Hard Thermal Loops on the Lattice
We develop a discrete lattice implementation of the hard thermal loop
effective action by the method of added auxiliary fields. We use the resulting
model to measure the sphaleron rate (topological susceptibility) of Yang-Mills
theory at weak coupling. Our results give parametric behavior in accord with
the arguments of Arnold, Son, and Yaffe, and are in quantitative agreement with
the results of Moore, Hu, and Muller.Comment: 43 pages, 6 figure
Electroweak Bubble Nucleation, Nonperturbatively
We present a lattice method to compute bubble nucleation rates at radiatively
induced first order phase transitions, in high temperature, weakly coupled
field theories, nonperturbatively. A generalization of Langer's approach, it
makes no recourse to saddle point expansions and includes completely the
dynamical prefactor. We test the technique by applying it to the electroweak
phase transition in the minimal standard model, at an unphysically small Higgs
mass which gives a reasonably strong phase transition (lambda/g^2 =0.036, which
corresponds to m(Higgs)/m(W) = 0.54 at tree level but does not correspond to a
positive physical Higgs mass when radiative effects of the top quark are
included), and compare the results to older perturbative and other estimates.
While two loop perturbation theory slightly under-estimates the strength of the
transition measured by the latent heat, it over-estimates the amount of
supercooling by a factor of 2.Comment: 48 pages, including 16 figures. Minor revisions and typo fixes,
nothing substantial, conclusions essentially unchange
Classical Sphaleron Rate on Fine Lattices
We measure the sphaleron rate for hot, classical Yang-Mills theory on the
lattice, in order to study its dependence on lattice spacing. By using a
topological definition of Chern-Simons number and going to extremely fine
lattices (up to beta=32, or lattice spacing a = 1 / (8 g^2 T)) we demonstrate
nontrivial scaling. The topological susceptibility, converted to physical
units, falls with lattice spacing on fine lattices in a way which is consistent
with linear dependence on (the Arnold-Son-Yaffe scaling relation) and
strongly disfavors a nonzero continuum limit. We also explain some unusual
behavior of the rate in small volumes, reported by Ambjorn and Krasnitz.Comment: 14 pages, includes 5 figure
Effective theory for the soft fluctuation modes in the spontaneously broken phase of the N-component scalar field theory
The effective dynamics of the low-frequency modes is derived for the O(N)
symmetric scalar field theory in the broken symmetry phase. The effect of the
high-frequency fluctuations is taken into account at one-loop level exactly. A
new length scale is shown to govern the long-time asymptotics of the linear
response function of the Goldstone modes. The large time asymptotic decay of an
arbitrary fluctuation is determined in the linear regime. We propose a set of
local equations for the numerical solution of the effective non-linear
dynamics. The applicability of the usual gradient expansion is carefully
assessed.Comment: 21 pages, LaTeX; final version to appear in Phys. Rev.
EMMI Rapid Reaction Task Force on "Thermalization in Non-abelian Plasmas"
Recently, different proposals have been put forward on how thermalization
proceeds in heavy-ion collisions in the idealized limit of very large nuclei at
sufficiently high energy. Important aspects of the parametric estimates at weak
coupling may be tested using well-established classical-statistical lattice
simulations of the far-from-equilibrium gluon dynamics. This has to be
confronted with strong coupling scenarios in related theories based on
gauge-string dualities. Furthermore, closely related questions about
far-from-equilibrium dynamics arise in early-universe cosmology and in
non-relativistic systems of ultracold atoms. These were central topics of the
EMMI Rapid Reaction Task Force meeting held on December 12-14, 2011, at the
University of Heidelberg, which we report on.Comment: 13 pages, summary of the EMMI Rapid Reaction Task Force on
"Thermalization in Non-abelian Plasmas", December 12-14, 2011, University of
Heidelberg, German
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