261 research outputs found
Preheating and phase transitions in gauge theories
It has recently been suggested that the baryon washout problem of the
standard electroweak baryogenesis scenario could be avoided if inflation ends
with a period of parametric resonance at a low enough energy density. I present
results of numerical simulations in which this process was studied in the
Abelian Higgs model. Our results show that because of the masslessness of the
gauge field, the parametric resonance takes place naturally, and that the
system reaches a quasi-equilibrium state in which the long-wavelength part of
the spectrum has a high effective temperature. This enhances baryon number
violation and makes baryogenesis more efficient.Comment: Talk given at SEWM2000. 5 pages, 1 figur
Formation of Magnetic Monopoles in Hot Gauge Theories
In this talk, I discuss the formation of magnetic monopoles in a phase
transition from the confining SU(2) phase to the Coulomb phase in a hot
Georgi-Glashow model. I argue that monopoles are formed from long-wavelength
thermal fluctuations, which freeze out after the phase transition.Comment: 5 pages, talk given at Strong and Electroweak Matter 2002,
Heidelberg, October 2-5, 200
Defect formation in the early universe
Topological defects are common in many everyday systems. In general, they
appear if a symmetry is broken at a rapid phase transition. In this article, I
explain why it is believed that they should have also been formed in the early
universe and how that would have happened. If topological defects are found,
this will provide a way to study observationally the first fractions of a
second after the Big Bang, but their apparent absence can also tell us many
things about the early universe.Comment: 26 pages, 10 figures. Updated to match the version published in
Contemporary Physics
(http://taylorandfrancis.metapress.com/link.asp?id=dcvj45hv41kr7xf7
Non-equilibrium dynamics of hot Abelian Higgs model
The real-time dynamics of finite-temperature gauge theories can be
approximated, to leading-order accuracy in the coupling constants, by a
classical field theory with the hard thermal loop Lagrangian. I show how this
approach can be used in numerical lattice simulations to study dynamics of the
Abelian Higgs model in or slightly out of equilibrium.Comment: 4 pages, talk given at COSMO' 99, Trieste, Italy, September 27 -
October 2, 199
Phase transition dynamics in the hot Abelian Higgs model
We present a detailed numerical study of the equilibrium and non-equilibrium
dynamics of the phase transition in the finite-temperature Abelian Higgs model.
Our simulations use classical equations of motion both with and without
hard-thermal-loop corrections, which take into account the leading quantum
effects. From the equilibrium real-time correlators, we determine the Landau
damping rate, the plasmon frequency and the plasmon damping rate. We also find
that, close to the phase transition, the static magnetic field correlator shows
power-law magnetic screening at long distances. The information about the
damping rates allows us to derive a quantitative prediction for the number
density of topological defects formed in a phase transition. We test this
prediction in a non-equilibrium simulation and show that the relevant time
scale for defect formation is given by the Landau damping rate.Comment: 22 pages, 3 figure
Lattice calculation of non-Gaussianity from preheating
If light scalar fields are present at the end of inflation, their
non-equilibrium dynamics such as parametric resonance or a phase transition can
produce non-Gaussian density perturbations. We show how these perturbations can
be calculated using non-linear lattice field theory simulations and the
separate universe approximation. In the massless preheating model, we find that
some parameter values are excluded while others lead to acceptable but
observable levels of non-Gaussianity. This shows that preheating can be an
important factor in assessing the viability of inflationary models.Comment: 4 pages, 1 figure; erratum adde
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