TY - JOUR
T1 - Gravitational waves and scalar perturbations from spectator fields
AU - Biagetti, Matteo
AU - Dimastrogiovanni, Emanuela
AU - Fasiello, Matteo
AU - Peloso, Marco
N1 - Publisher Copyright:
© 2015 IOP Publishing Ltd and Sissa Medialab srl.
PY - 2015/4/8
Y1 - 2015/4/8
N2 - 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 1014GeV. 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 cs 蠐 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 cs, thus breaking the direct r 虠 H connection.
AB - 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 1014GeV. 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 cs 蠐 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 cs, thus breaking the direct r 虠 H connection.
KW - inflation
KW - physics of the early universe
KW - primordial gravitational waves (theory)
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U2 - 10.1088/1475-7516/2015/04/011
DO - 10.1088/1475-7516/2015/04/011
M3 - Article
AN - SCOPUS:84927521145
SN - 1475-7516
VL - 2015
SP - 11
JO - Journal of Cosmology and Astroparticle Physics
JF - Journal of Cosmology and Astroparticle Physics
IS - 4
ER -