Gravitational waves and scalar perturbations from spectator fields
- Département de Physique Théorique and Centre for Astroparticle Physics (CAP), Université de Genève, 24 quai E. Ansermet, CH-1211 Genève (Switzerland)
- School of Physics and Astronomy, University of Minnesota, Minneapolis, MN 55455 (United States)
- CERCA and Department of Physics, Case Western Reserve University, Cleveland (United States)
The most conventional mechanism for gravitational waves (gw) production during inflation is the amplification of vacuum metric fluctuations. In this case the gw production can be uniquely related to the inflationary expansion rate H. For example, a gw detection close to the present experimental limit (tensor-to-scalar ratio r ∼ 0.1) would indicate an inflationary expansion rate close to 10{sup 14} GeV. This conclusion, however, would be invalid if the observed gw originated from a different source. We construct and study one of the possible covariant formulations of the mechanism suggested in [1], where a spectator field σ with a sound speed c{sub s} || 1 acts as a source for gw during inflation. In our formulation σ is described by a so-called P(X) Lagrangian and a non-minimal coupling to gravity. This field interacts only gravitationally with the inflaton, which has a standard action. We compute the amount of scalar and tensor density fluctuations produced by σ and find that, in our realization, r is not enhanced with respect to the standard result but it is strongly sensitive to c{sub s}, thus breaking the direct r ↔ H connection.
- OSTI ID:
- 22525909
- Journal Information:
- Journal of Cosmology and Astroparticle Physics, Vol. 2015, Issue 04; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 1475-7516
- Country of Publication:
- United States
- Language:
- English
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