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More fields are different: Stochastic view of multifield inflationary scenario

Tomo Takahashi*

Koki Tokeshi†

  • *Contact author: tomot@cc.saga-u.ac.jp
  • †Contact author: tokeshi@icrr.u-tokyo.ac.jp
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Phys. Rev. D 114, L101301 – Published 9 November, 2026

DOI: https://doi.org/10.1103/fqtz-p73d

Abstract

High-energy physics often motivates multifield inflationary scenarios where stochastic effects play a crucial role. Peculiar to multifield models, the noise-induced centrifugal force results in a longer duration of inflation depending on the number of fields, even when the stochastic noises themselves are small. We show that, in such small-noise regimes, the number of fields generically discriminates whether inflation successfully terminates or lasts forever. Our results indicate that inflation with an extremely large number of fields may fail to realize our observable Universe.

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  34. Reference [22] found another critical number of fields, d≷p, based on a different assumption from ours, and, therefore, there is no contradiction. The critical value in Ref. [22] is controlled by the reflective boundary regardless of all the other parameters, while our bound depends not only on p, but also v0 and r, in the small-noise regime where the location of the reflective boundary is irrelevant.

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Information

Phys. Rev. D 114, L101301– Published 9 November, 2026
  • Received 30 April 2025
  • Accepted 19 October 2026
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