New constraints on multifield inflation with nonminimal coupling

Shinji Tsujikawa*, Hiroki Yajima

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

29 Citations (Scopus)


We study the dynamics and perturbations during inflation and reheating in a multifield model where a second scalar field χ is nonminimally coupled to the scalar curvature (1/2ξRχ2). When ξ is positive, the usual inflationary prediction for large-scale anisotropies is hardly altered while the χ fluctuation in sub-Hubble modes can be amplified during preheating for large ξ. For negative values of ξ, however, long-wave modes of the χ fluctuation exhibit exponential increase during inflation, leading to the strong enhancement of super-Hubble metric perturbations even when |ξ| is less than unity. This is because the effective χ mass becomes negative during inflation. We constrain the strength of ξ and the initial χ by the amplitude of produced density perturbations. One way to avoid nonadiabatic growth of super-Hubble curvature perturbations is to stabilize the χ mass through a coupling to the inflaton. Preheating may thus be necessary in these models to protect the stability of the inflationary phase.

Original languageEnglish
Article number123512
Pages (from-to)1-13
Number of pages13
JournalPhysical Review D - Particles, Fields, Gravitation and Cosmology
Issue number12
Publication statusPublished - 2000 Dec 15

ASJC Scopus subject areas

  • Physics and Astronomy (miscellaneous)


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