693 research outputs found
The Hartree ensemble approximation revisited: The "symmetric phase"
The Hartree ensemble approximation is studied in the ``symmetric phase'' of
1+1 dimensional lambda phi^4 theory. In comparison with the ``broken phase''
studied previously, it is shown that the dynamical evolution of observables
such as the particle distribution, energy exchange and auto-correlation
functions, is substantially slower. Approximate thermalization is found only
for relatively large energy densities and couplings.Comment: 17 pages RevTeX, 16 figures, 3 tables, uses amsmath and feynmp.
Extended some sections, reordered Sec.IV, added 3 refs, numerical typo
corrected, published versio
Finiteness of Hot Classical Scalar Field Theory and the Plasmon Damping Rate
We investigate the renormalizability of the classical theory at
finite temperature. We calculate the time-dependent two point function to two
loop order and show that it can be rendered finite by the counterterms of the
classical static theory. As an application the classical plasmon damping rate
is found to be . When we use the high
temperature expression for given by dimensional reduction, the rate is
found to agree with the quantum mechanical result.Comment: 11 pages, 4 eps figures, minor typographic corrections and two
references adde
Staying Thermal with Hartree Ensemble Approximations
We study thermal behavior of a recently introduced Hartree ensemble
approximation, which allows for non-perturbative inhomogeneous field
configurations as well as for approximate thermalization, in the model
in 1+1 dimensions. Using ensembles with a free field thermal distribution as
out-of-equilibrium initial conditions we determine thermalization time scales.
The time scale for which the system stays in approximate quantum thermal
equilibrium is an indication of the time scales for which the approximation
method stays reasonable. This time scale turns out to be two orders of
magnitude larger than the time scale for thermalization, in the range of
couplings and temperatures studied. We also discuss simplifications of our
method which are numerically more efficient and make a comparison with
classical dynamics.Comment: 19 pages latex; extensively rewritten to improve presentation, data
essentially unchanged, analysis sharpened and one table adde
Particle distributions in electroweak tachyonic preheating
We consider the out-of-equilibrium (quasi-) particle number distributions of
the Higgs and W-fields during electroweak tachyonic preheating. We model this
process by a fast quench, and perform classical real-time lattice simulations
in the SU(2)-Higgs model in three dimensions. We discuss how to define particle
numbers and effective energies using two-point functions in Coulomb and unitary
gauge, and consider some of the associated problems. After an initial
exponential growth in effective particle numbers, the system stabilises,
allowing us to extract effective masses, temperatures and chemical potentials
for the particles.Comment: 3 pages, Lattice2003(higgs
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