Homogeneous Mean Fields
These codes solve for the time evolution of mean fields in the
presence of self-consistently determined quantum fluctuations. The
equations being solved are in the leading order 1/N approximation
where the mean field interacts with the fluctuations but the
fluctuations do not interact with each other directly. Appropriate
renormalizations ensure that all physical quantities are independent
of cut-offs.
This class of codes is designed to investigate the time evolution
of mean fields to study problems such as the formation and evolution
of defects and disoriented chiral condensates after a rapid quench,
the efficiency of baryogenesis in the electroweak phase transition,
and preheating in inflation. The numerical issue in these codes is to
solve the mean field evolution equation with a driving term that
incorporates the cumulative effects of fluctuations concurrently with
solving for the fluctuation modes which have time-dependent masses
determined in turn by the time-evolving mean field.
The fluctuations are solved for in momentum space using a momentum
grid with mode numbers ranging from tens of thousands to hundreds of
thousands. Extreme accuracy is an essential requirement because of the
long durations over which the evolution is tracked. The mode equations
are stepped using a sixth-order adaptive time step RK integrator which
allows energy conservation to a few parts per million over the
temporal range of typical evolutions.
Codes for backreaction of scalar field theories on curved spacetimes
will be tested. No production runs are planned.
| Salman Habib / LANL / habib@lanl.gov / revised August 00 |
 |