English

Multiple Fields in Stochastic Inflation

High Energy Physics - Theory 2016-08-24 v2 Cosmology and Nongalactic Astrophysics General Relativity and Quantum Cosmology High Energy Physics - Phenomenology

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 ee-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 ee-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 ee-folds can be used to calculate the distribution of primordial density perturbations in the stochastic-δN\delta N formalism.

Keywords

Cite

@article{arxiv.1604.04502,
  title  = {Multiple Fields in Stochastic Inflation},
  author = {Hooshyar Assadullahi and Hassan Firouzjahi and Mahdiyar Noorbala and Vincent Vennin and David Wands},
  journal= {arXiv preprint arXiv:1604.04502},
  year   = {2016}
}

Comments

20 pages without appendices (total 30 pages), 5 figures, 1 table. matches published version in JCAP (references added)

R2 v1 2026-06-22T13:33:19.937Z