Time scales for nonlinear processes in preheating after multifield inflation with nonminimal couplings

Physical review. D/Physical review. D., vol. 102

Abstract

We have conducted extensive lattice simulations to study the postinflation dynamics of multifield models involving nonminimal couplings. We explore the parameter dependence of preheating in these models and describe the various time scales that control such nonlinear processes as energy transfer, rescattering, and the approach to radiation domination and thermalization. In the limit of large nonminimal couplings (${\ensuremath{\xi}}_{I}\ensuremath{\sim}100$), we find that efficient transfer of energy from the inflaton condensate to radiative degrees of freedom, emergence of a radiation-dominated equation of state, and the onset of thermalization each consistently occur within ${N}_{\mathrm{reh}}\ensuremath{\lesssim}3$ $e$-folds after the end of inflation, largely independent of the values of the other couplings in the models. The exception is the case of negative ellipticity, in which there is a misalignment between the dominant direction in field space along which the system evolves and the larger of the nonminimal couplings ${\ensuremath{\xi}}_{I}$. In those cases, the field-space-driven parametric resonance is effectively shut off. More generally, the competition between the scalar fields' potential and the field-space manifold structure can yield interesting phenomena such as two-stage resonances. Across many regions of parameter space, we find efficient re-scattering between the distinct fields, leading to a partial memory loss of the shape of the initial fluctuation spectrum. Despite the explosive particle production, which can lead to a quick depletion of the background energy density, the nonlinear processes do not induce any superhorizon correlations after the end of inflation in these models, which keeps predictions for cosmic microwave background observables unaffected by the late-time amplification of isocurvature fluctuations. Hence the excellent agreement between primordial observables and recent observations is preserved for this class of models, even when we consider postinflation dynamics.

Authors 5

1. Jorinde van de Vis

   Deutsches Elektronen-Synchrotron DESY

   Affiliation as printed

   DESY, Notkestraße 85, D-22607 Hamburg, Germany

2. Rachel Nguyen

   University of Illinois Urbana-Champaign · Kenyon College

   Affiliation as printed

   Department of Physics, Kenyon College, Gambier, Ohio 43022, USA

   Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA

3. Evangelos I. Sfakianakis Aachen Lorentz Institute for Theoretical Physics

   Leiden University · National Institute for Subatomic Physics

   Affiliation as printed

   Lorentz Institute for Theoretical Physics, Leiden University, 2333CA Leiden, The Netherlands

   Nikhef, Science Park 105, 1098XG Amsterdam, The Netherlands

4. John T. Giblin

   Kenyon College · Case Western Reserve University

   Affiliation as printed

   CERCA/ISO, Department of Physics, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, Ohio 44106, USA

   Department of Physics, Kenyon College, Gambier, Ohio 43022, USA

5. David I. Kaiser

   Massachusetts Institute of Technology

   Affiliation as printed

   Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA