31 research outputs found
Quantum field dynamics of the slow rollover in the linear delta expansion
We show how the linear delta expansion, as applied to the slow-roll
transition in quantum mechanics, can be recast in the closed time-path
formalism. This results in simpler, explicit expressions than were obtained in
the Schr\"odinger formulation and allows for a straightforward generalization
to higher dimensions. Motivated by the success of the method in the
quantum-mechanical problem, where it has been shown to give more accurate
results for longer than existing alternatives, we apply the linear delta
expansion to four-dimensional field theory.
At small times all methods agree. At later times, the first-order linear
delta expansion is consistently higher that Hartree-Fock, but does not show any
sign of a turnover. A turnover emerges in second-order of the method, but the
value of at the
turnover. In subsequent applications of the method we hope to implement the
calculation in the context of an expanding universe, following the line of
earlier calculations by Boyanovsky {\sl et al.}, who used the Hartree-Fock and
large-N methods. It seems clear, however, that the method will become
unreliable as the system enters the reheating stage.Comment: 17 pages, 9 figures, revised version with extra section 4.2 including
second order calculatio