Statistics – Applications
Scientific paper
Dec 1997
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1997phdt.........5r&link_type=abstract
Thesis (PHD). UNIVERSITY OF MARYLAND COLLEGE PARK , Source DAI-B 58/11, p. 6035, May 1998, 202 pages.
Statistics
Applications
1
Scientific paper
The nonequilibrium dynamics of quantum fields is studied in inflationary cosmology, with particular emphasis on applications to the problem post-inflation reheating. The Schwinger-Keldysh closed-time-path (CTP) formalism is utilized along with the two-particle-irreducible (2PI) effective action in order to obtain coupled, nonperturbative equations for the mean field and variance in a general curved background spacetime, both as a closed system in the case of a self-interacting inflaton field, and as an open system in the case of coarse-grained dynamics of the inflaton field interacting with fermions. For a model consisting of a quartically self-interacting O(N) field theory (with unbroken symmetry) in spatially flat FRW spacetime, the dynamics of the mean field is studied numerically, at leading order in the large-N expansion, with initial conditions appropriate to the end state of slow roll in chaotic inflation scenarios. The time evolution of the scale factor is determined self-consistently using the semiclassical Einstein equation. It is found that cosmic expansion can dramatically affect the efficiency of parametric resonance-induced particle production. The production of fermions due to the oscillating inflation mean field is studied for the case of a scalar inflaton coupled to a fermion field via a Yukawa coupling f. The dissipation and noise kernels appearing at O(f2) in the one-loop CTP effective action are shown to satisfy a zero-temperature fluctuation-dissipation relation (FDR). The normal-threshold O(f4) parts of the one-loop CTP effective action are also shown to satisfy a FDR. The effective stochastic equation obeyed by the inflaton zero mode at O(f4) is contains multiplicative noise. It is shown that stochasticity becomes important to the dynamics of the inflaton zero mode before the end of reheating. The thermalization problem is discussed, and a strategy is presented for obtaining time-local equations for equal-time correlation functions which goes beyond the Hartree-Fock approximation. For the λPhi4 field theory, the correlation entropy associated with a particular coarse graining scheme consisting of slaving the three-point function to the mean field and two-point function is computed, and found not to be conserved.
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