arXiv subjects

Tomohiro Fujita

Publications and source records attributed to Tomohiro Fujita.

93 records · Page 6Linked to original sources

arXiv2013

A new algorithm for calculating the curvature perturbations in stochastic inflation

We propose a new approach for calculating the curvature perturbations produced during inflation in the stochastic formalism. In our formalism, the fluctuations of the e-foldings are directly calculated without perturbatively expanding the inflaton field and they are connected to the curvature perturbations by the $δN$ formalism. The result automatically includes the contributions of the higher order perturbations because we solve the equation of motion non-perturbatively. In this paper, we analytically prove that our result (the power spectrum and the nonlinearity parameter) is consistent with the standard result in single field slow-roll inflation. We also describe the algorithm for numerical calculations of the curvature perturbations in more general inflation models.

astro-ph.CO↗

arXiv2013

Higher order statistics of curvature perturbations in IFF model and its Planck constraints

We compute the power spectrum P_ζ, and non-linear parameters f_nl and τ_nl of the curvature perturbation induced during inflation by the electromagnetic fields in the kinetic coupling model (IFF model). By using the observational result of P_ζ, f_nl and τ_nl reported by the Planck collaboration, we study the constraint on the model comprehensively. Interestingly, if the single slow-rolling inflaton is responsible for the observed P_ζ, the constraint from τ_nl is most stringent. We also find a general relationship between f_nl and τ_nl generated in this model. Even if f_nl \sim O(1), a detectable τ_nl can be produced.

astro-ph.CO↗

arXiv2012

Universal upper limit on inflation energy scale from cosmic magnetic field

Recently observational lower bounds on the strength of cosmic magnetic fields were reported, based on gamma-ray flux from distant blazars. If inflation is responsible for the generation of such magnetic fields then the inflation energy scale is bounded from above as rho_{inf}^{1/4} < 2.5 times 10^{-7}M_{Pl} times (B_{obs}/10^{-15}G)^{-2} in a wide class of inflationary magnetogenesis models, where B_{obs} is the observed strength of cosmic magnetic fields. The tensor-to-scalar ratio is correspondingly constrained as r< 10^{-19} times (B_{obs}/10^{-15}G)^{-8}. Therefore, if the reported strength B_{obs} \geq 10^{-15}G is confirmed and if any signatures of gravitational waves from inflation are detected in the near future, then our result indicates some tensions between inflationary magnetogenesis and observations.

astro-ph.CO↗