2,839 research outputs found
Curvature Spectra and Nongaussianities in the Roulette Inflation Model
Using the gradient expansion method of Rigopoulos, Shellard and van Tent
which treats cosmological perturbations as gradients on top of a homogeneous
and isotropic FRW background, we study the production of nongaussianities in
the roulette model of inflation. Investigating a number of trajectories within
this two-field model of inflation, we find that while the superhorizon
influence of the isocurvature modes on the curvature bispectrum produces
nonzero contribution to f_NL, the effect is negligible next to the standard
inflationary prediction |f_NL| ~ n_s - 1. This is the case in both the squeezed
and equilateral configurations of the bispectrum, although the former is
slightly larger in the trajectories under consideration.Comment: 23 pages, 6 figures, 3 tables, 1 appendix; Added references, slightly
extended section
Spectral analysis of the high-energy IceCube neutrinos
A full energy and flavor-dependent analysis of the three-year high-energy
IceCube neutrino events is presented. By means of multidimensional fits, we
derive the current preferred values of the high-energy neutrino flavor ratios,
the normalization and spectral index of the astrophysical fluxes, and the
expected atmospheric background events, including a prompt component. A crucial
assumption resides on the choice of the energy interval used for the analyses,
which significantly biases the results. When restricting ourselves to the ~30
TeV - 3 PeV energy range, which contains all the observed IceCube events, we
find that the inclusion of the spectral information improves the fit to the
canonical flavor composition at Earth, (1:1:1), with respect to a single-energy
bin analysis. Increasing both the minimum and the maximum deposited energies
has dramatic effects on the reconstructed flavor ratios as well as on the
spectral index. Imposing a higher threshold of 60 TeV yields a slightly harder
spectrum by allowing a larger muon neutrino component, since above this energy
most atmospheric tracklike events are effectively removed. Extending the
high-energy cutoff to fully cover the Glashow resonance region leads to a
softer spectrum and a preference for tau neutrino dominance, as none of the
expected electron antineutrino induced showers have been observed so far. The
lack of showers at energies above 2 PeV may point to a broken power-law
neutrino spectrum. Future data may confirm or falsify whether or not the
recently discovered high-energy neutrino fluxes and the long-standing detected
cosmic rays have a common origin.Comment: 33 pages, 13 figures. v3: one extra figure (fig. 13), some references
updated and some formulae moved to the Appendix. It matches version published
in PR
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