On the waterfall behavior in hybrid inflation

We revisit the hybrid inflation model focusing on the dynamics of the waterfall field in an analytical way. It is shown that inflation may last long enough during the waterfall regime for some parameter regions, confirming the claim of Clesse. In this case the scalar spectral index becomes red, and can fall into the best fit range of the WMAP observation.Comment: 10 pages, 9 figure

Can decaying particle explain cosmic infrared background excess?

Recently the CIBER experiment measured the diffuse cosmic infrared background (CIB) flux and claimed an excess compared with integrated emission from galaxies. We show that the CIB spectrum can be fitted by the additional photons produced by the decay of a new particle. However, it also contributes too much to the anisotropy of the CIB, which is in contradiction with the anisotropy measurements by the CIBER and Hubble Space Telescope.Comment: 14 pages, 3 figure

Stochastic Gravitational Waves from Particle Origin

We propose that there may be a substantial stochastic gravitational wave background from particle origin, mainly from the gravitational three-body decay of the inflaton. The emitted gravitons could constitute a sizable contribution to dark radiation if the mass of inflaton is close to the Planck scale, which can be probed by future CMB experiments that have a sensitivity on the deviation of the effective number of neutrinos in the standard cosmology, $\delta N_{\textrm{eff}}\sim 0.02 - 0.03$. We have also illustrated the spectrum of the radiated gravitational waves, in comparison to the current and future experiments, and found that gravitational waves from particle origin could be the dominant contribution to the energy density at high-frequency domain, but beyond the sensitivity regions of various experiments.Comment: 1+13 pages, 6 figure

Late-time Affleck-Dine baryogenesis after thermal inflation

Thermal inflation can solve serious cosmological problems such as overproduction of gravitinos and moduli. However, it also dilutes the preexisting baryon asymmetry. We investigate a possibility that Affleck-Dine mechanism works after thermal inflation and generate the baryon number at an acceptable level using lattice calculation. We find that a proper amount of baryon number can be generated for appropriate model parameters.Comment: 6 pages, 5 figures, reference adde

Higgs Chaotic Inflation and the Primordial B-mode Polarization Discovered by BICEP2

We show that the standard model Higgs field can realize the quadratic chaotic inflation, if the kinetic term is significantly modified at large field values. This is a simple realization of the so-called running kinetic inflation. The point is that the Higgs field respects an approximate shift symmetry at high energy scale. The tensor-to-scalar ratio is predicted to be $r \simeq 0.13 - 0.16$, which nicely explains the primordial B-mode polarization, $r=0.20^{+0.07}_{-0.05}$, recently discovered by the BICEP2 experiment. In particular, allowing small modulations induced by the shift symmetry breaking, the negative running spectral index can also be induced. The reheating temperature is expected to be so high that successful thermal leptogenesis is possible. The suppressed quartic coupling of the Higgs field at high energy scales may be related to the Higgs chaotic inflation.Comment: 12 pages. v2: discussion improved, references added. v3: matches with published versio

PeV-scale Supersymmetry from New Inflation

We show that heavy supersymmetric particles around O(100) TeV to O(1) PeV naturally appear in new inflation in which the Higgs boson responsible for the breaking of U(1)B-L plays the role of inflaton. Most important, the supersymmetric breaking scale is bounded above by the inflationary dynamics, in order to suppress the Coleman-Weinberg potential which would otherwise spoil the slow-roll inflation. Our scenario has rich phenomenological and cosmological implications: the Higgs boson mass at around 125 GeV can be easily explained, non-thermal leptogenesis works automatically, the gravitino production from inflaton decay is suppressed, the dark matter is either the lightest neutralino or the QCD axion, and the upper bound on the inflation scale for the modulus stabilization can be marginally satisfied.Comment: 34 pages, 8 figures. v2: references adde