Large Nonlocal Non-Gaussianity from a Curvaton Brane

We use a generalized delta N formalism to study the generation of the primordial curvature perturbation in the curvaton brane scenario inspired by stringy compactifications. We note that the non-Gaussian features, especially the trispectra, crucially depend on the decay mechanism in a general curvaton scenario. Specifically, we study the bispectra and trispectra of the curvaton brane model in detail to illustrate the importance of curvaton decay in generating nonlinear fluctuations. When the curvaton brane moves nonrelativistically during inflation, the shape of non-Gaussianity is local, but the corresponding size is different from that in the standard curvaton scenario. When the curvaton brane moves relativistically in inflationary stage, the shape of non-Gaussianity is of equilateral type.Comment: 24 pages, 2 figure

ADAPTIVE FEC WITH DYNAMICALLY BLOCK SIZE CONTROL FOR VIDEO STREAMING OVER WIRELESS NETWORK

[[conferencetype]]國際[[conferencedate]]20150722~20150724[[iscallforpapers]]Y[[conferencelocation]]Osaka,Japa

Doppler effect of gamma-ray bursts in the fireball framework

The influence of the Doppler effect in the fireball framework on the spectrum of gamma-ray bursts is investigated. The study shows that the shape of the expected spectrum of an expanding fireball remains almost the same as that of the corresponding rest frame spectrum for constant radiations of the bremsstrahlung, Comptonized, and synchrotron mechanisms as well as for that of the GRB model. The peak flux spectrum and the peak frequency are obviously correlated. When the value of the Lorentz factor becomes 10 times larger, the flux of fireballs would be several orders of magnitude larger. The expansion speed of fireballs is a fundamental factor of the enhancement of the flux of gamma-ray bursts.Comment: 19 pages, 13 figure

Cosmology of F(R) nonlinear massive gravity

The theory of nonlinear massive gravity can be extended into the F(R) form as developed in Phys.Rev.D90, 064051 (2014). Being free of the Boulware-Deser ghost, such a construction has the additional advantage of exhibiting no linear instabilities around a cosmological background. We investigate various cosmological evolutions of a universe governed by this generalized massive gravitational theory. Specifically, under the Starobinsky ansantz, this model provides a unified description of the cosmological history, from early-time inflation to late-time self-acceleration. Moreover, under viable F(R) forms, the scenario leads to a very interesting dark-energy phenomenology, including the realization of the quintom scenario without any pathology. Finally, we provide a detailed analysis of the cosmological perturbations at linear order, as well as the Hamiltonian constraint analysis, in order to examine the physical degrees of freedom.Comment: 15 pages, 6 figures, version published in Phys. Rev.