TY - JOUR
T1 - Observable non-Gaussianity from gauge field production in slow roll inflation, and a challenging connection with magnetogenesis
AU - Barnaby, Neil
AU - Namba, Ryo
AU - Peloso, Marco
PY - 2012/6/14
Y1 - 2012/6/14
N2 - In any realistic particle physics model of inflation, the inflaton can be expected to couple to other fields. We consider a model with a dilatonlike coupling between a U(1) gauge field and a scalar inflaton. We show that this coupling can result in observable non-Gaussianity, even in the conventional regime where inflation is supported by a single scalar slowly rolling on a smooth potential: the time-dependent inflaton condensate leads to amplification of the large-scale gauge field fluctuations, which can feed back into the scalar/tensor cosmological perturbations. In the squeezed limit, the resulting bispectrum is close to the local one, but it shows a sizable and characteristic quadrupolar dependence on the angle between the shorter and the larger modes in the correlation. Observable non-Gaussianity is obtained in a regime where perturbation theory is under control. If the gauge field is identified with the electromagnetic field, the model that we study is a realization of the magnetogenesis idea originally proposed by Ratra, and widely studied. This identification (which is not necessary for the non-Gaussianity production) is however problematic in light of a strong coupling problem already noted in the literature.
AB - In any realistic particle physics model of inflation, the inflaton can be expected to couple to other fields. We consider a model with a dilatonlike coupling between a U(1) gauge field and a scalar inflaton. We show that this coupling can result in observable non-Gaussianity, even in the conventional regime where inflation is supported by a single scalar slowly rolling on a smooth potential: the time-dependent inflaton condensate leads to amplification of the large-scale gauge field fluctuations, which can feed back into the scalar/tensor cosmological perturbations. In the squeezed limit, the resulting bispectrum is close to the local one, but it shows a sizable and characteristic quadrupolar dependence on the angle between the shorter and the larger modes in the correlation. Observable non-Gaussianity is obtained in a regime where perturbation theory is under control. If the gauge field is identified with the electromagnetic field, the model that we study is a realization of the magnetogenesis idea originally proposed by Ratra, and widely studied. This identification (which is not necessary for the non-Gaussianity production) is however problematic in light of a strong coupling problem already noted in the literature.
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U2 - 10.1103/PhysRevD.85.123523
DO - 10.1103/PhysRevD.85.123523
M3 - Article
AN - SCOPUS:84862277868
SN - 1550-7998
VL - 85
JO - Physical Review D - Particles, Fields, Gravitation and Cosmology
JF - Physical Review D - Particles, Fields, Gravitation and Cosmology
IS - 12
M1 - 123523
ER -