6 research outputs found
Optimal Jet Finder
We describe a FORTRAN 77 implementation of the optimal jet definition for
identification of jets in hadronic final states of particle collisions. We
discuss details of the implementation, explain interface subroutines and
provide a usage example. The source code is available from
http://www.inr.ac.ru/~ftkachov/projects/jets/Comment: version to appear in Comp. Phys. Commun., 36 page
Chern-Simons production during preheating in hybrid inflation models
We study the onset of symmetry breaking after hybrid inflation in a model
having the field content of the SU(2) gauge-scalar sector of the standard
model, coupled to a singlet inflaton. This process is studied in
(3+1)-dimensions in a fully non-perturbative way with the help of lattice
techniques within the classical approximation. We focus on the role played by
gauge fields and, in particular, on the generation of Chern-Simons number. Our
results are shown to be insensitive to the various cut-offs introduced in our
numerical approach. The spectra preserves a large hierarchy between long and
short-wavelength modes during the whole period of symmetry breaking and
Chern-Simons generation, confirming that the dynamics is driven by the low
momentum sector of the theory. We establish that the Chern-Simons production
mechanism is associated with local sphaleron-like structures. The corresponding
sphaleron rates are of order 10^{-5} m^4, which, within certain scenarios of
electroweak baryogenesis and a (not unnaturally large) additional source of CP
violation, could explain the present baryon asymmetry of the universe.Comment: 28 pages, 15 figures, ReVTeX. With minor corrections, version to
appear in Phys. Rev.
Quantum dynamics and thermalization for out-of-equilibrium phi^4-theory
The quantum time evolution of \phi^4-field theory for a spatially homogeneous
system in 2+1 space-time dimensions is investigated numerically for
out-of-equilibrium initial conditions on the basis of the Kadanoff-Baym
equations including the tadpole and sunset self-energies. Whereas the tadpole
self-energy yields a dynamical mass, the sunset self-energy is responsible for
dissipation and an equilibration of the system. In particular we address the
dynamics of the spectral (`off-shell') distributions of the excited quantum
modes and the different phases in the approach to equilibrium described by
Kubo-Martin-Schwinger relations for thermal equilibrium states. The
investigation explicitly demonstrates that the only translation invariant
solutions representing the stationary fixed points of the coupled equation of
motions are those of full thermal equilibrium. They agree with those extracted
from the time integration of the Kadanoff-Baym equations in the long time
limit. Furthermore, a detailed comparison of the full quantum dynamics to more
approximate and simple schemes like that of a standard kinetic (on-shell)
Boltzmann equation is performed. Our analysis shows that the consistent
inclusion of the dynamical spectral function has a significant impact on
relaxation phenomena. The different time scales, that are involved in the
dynamical quantum evolution towards a complete thermalized state, are discussed
in detail. We find that far off-shell 1 3 processes are responsible for
chemical equilibration, which is missed in the Boltzmann limit. Finally, we
address briefly the case of (bare) massless fields. For sufficiently large
couplings we observe the onset of Bose condensation, where our scheme
within symmetric \phi^4-theory breaks down.Comment: 77 pages, 26 figure
Stochastic Production Of Kink-Antikink Pairs In The Presence Of An Oscillating Background
We numerically investigate the production of kink-antikink pairs in a
dimensional field theory subject to white noise and periodic driving.
The twin effects of noise and periodic driving acting in conjunction lead to
considerable enhancement in the kink density compared to the thermal
equilibrium value, for low dissipation coefficients and for a specific range of
frequencies of the oscillating background. The dependence of the kink-density
on the temperature of the heat bath, the amplitude of the oscillating
background and value of the dissipation coefficient is also investigated. An
interesting feature of our result is that kink-antikink production occurs even
though the system always remains in the broken symmetry phase.Comment: Revtex, 21 pages including 7 figures; more references adde