Multiple fields in stochastic inflation

Hooshyar Assadullahi, Hassan Firouzjahi, Mahdiyar Noorbala, Vincent Vennin, David Wands

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Abstract

Stochastic effects in multi-field inflationary scenarios are investigated. A hierarchy of diffusion equations is derived, the solutions of which yield moments of the numbers of inflationary e-folds. Solving the resulting partial differential equations in multi-dimensional field space is more challenging than the single-field case. A few tractable examples are discussed, which show that the number of fields is, in general, a critical parameter. When more than two fields are present for instance, the probability to explore arbitrarily large-field regions of the potential, otherwise inaccessible to single-field dynamics, becomes non-zero. In some configurations, this gives rise to an infinite mean number of e-folds, regardless of the initial conditions. Another difference with respect to single-field scenarios is that multi-field stochastic effects can be large even at sub-Planckian energy. This opens interesting new possibilities for probing quantum effects in inflationary dynamics, since the moments of the numbers of e-folds can be used to calculate the distribution of primordial density perturbations in the stochastic-δ N formalism.
Original languageEnglish
Article number043
Number of pages32
JournalJournal of Cosmology and Astroparticle Physics
Volume2016
Issue number06
DOIs
Publication statusPublished - 24 Jun 2016

Keywords

  • RCUK
  • STFC
  • ST/K00090X/1
  • ST/N000668/1
  • inflation
  • quantum gravity phenomenology

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