Non-Gaussianity from violation of slow-roll in multiple inflation
ArXiv 0910.3373 (2009)
Abstract:
Multiple inflation is a model based on N=1 supergravity wherein there are sudden changes in the mass of the inflaton because it couples to 'flat direction' scalar fields which undergo symmetry breaking phase transitions as the universe cools. The resulting brief violations of slow-roll evolution generate a non-gaussian signal which we find to be oscillatory and yielding f_NL ~ 5-20. This is potentially detectable by e.g. Planck but would require new bispectrum estimators to do so. We also derive a model-independent result relating the period of oscillations of a phase transition during inflation to the period of oscillations in the primordial curvature perturbation generated by the inflaton.Non-Gaussianity from violation of slow-roll in multiple inflation
(2009)
On cosmic ray acceleration in supernova remnants and the FERMI/PAMELA data
ArXiv 0909.4060 (2009)
Abstract:
We discuss recent observations of high energy cosmic ray positrons and electrons in the context of hadronic interactions in supernova remnants, the suspected accelerators of galactic cosmic rays. Diffusive shock acceleration can harden the energy spectrum of secondary positrons relative to that of the primary protons (and electrons) and thus explain the rise in the positron fraction observed by PAMELA above 10 GeV. We normalize the hadronic interaction rate by holding pion decay to be responsible for the gamma-rays detected by HESS from some SNRs. By simulating the spatial and temporal distribution of SNRs in the Galaxy according to their known statistics, we are able to then fit the electron (plus positron) energy spectrum measured by Fermi. It appears that IceCube has good prospects for detecting the hadronic neutrino fluxes expected from nearby SNRs.On cosmic ray acceleration in supernova remnants and the FERMI/PAMELA data
(2009)
Testing astrophysical models for the PAMELA positron excess with cosmic ray nuclei.
Phys Rev Lett 103:8 (2009) 081104