3,103 research outputs found
Weak Gravity Conjecture with Large Extra Dimensions
In the presence of large extra dimensions, the fundamental Planck scale can
be much lower than the apparent four-dimensional Planck scale. In this setup,
the weak gravity conjecture implies a much more stringent constraint on the UV
cutoff for the U(1) gauge theory in four dimensions. This new energy scale may
be relevant to LHC.Comment: 8 pages; Refs added, version for publication in PL
Spectral Index in Curvaton Scenario
A red tilted primordial power spectrum is preferred by WMAP five-year data
and a large positive local-type non-Gaussianity might be observed as
well. In this short note we find that a red tilted and large non-Gaussian
primordial power spectrum cannot be naturally obtained in curvaton model,
because is related to the initial condition of inflation.Comment: 12 pages; refs adde
An analytic calculation of the growth index for dark energy model
We derive the analytic formula of the growth index for dark energy
model where the effect on the growth of matter density perturbation
from modified gravity (MG) is encoded in the effective Newton coupling constant
in MG (or equivalently ). Based on the
analytic formula, we propose that the parameter can be directly figured out
by comparing the observed growth rate to the
prediction of in general relativity.Comment: 5 pages, 1 figure; refs added; minor revised, version accepted by
EPJ
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