26,194 research outputs found
Large Scale Structure Formation of Normal Branch in DGP Brane World Model
In this paper, we study the large scale structure formation of the normal
branch in DGP model (Dvail, Gabadadze and Porrati brane world model) by
applying the scaling method developed by Sawicki, Song and Hu for solving the
coupled perturbed equations of motion of on-brane and off-brane. There is
detectable departure of perturbed gravitational potential from LCDM even at the
minimal deviation of the effective equation of state w_eff below -1. The
modified perturbed gravitational potential weakens the integrated Sachs-Wolfe
effect which is strengthened in the self-accelerating branch DGP model.
Additionally, we discuss the validity of the scaling solution in the de Sitter
limit at late times.Comment: 6 pages, 2 figure
Analytic approximations, perturbation theory, effective field theory methods and their applications
We summarize the parallel session B4: 'Analytic approximations, perturbation
theory effective field theory methods and their applications' and the joint
session B2/B4: 'Approximate solutions to Einstein equations: Methods and
Applications', of the GR20 & Amaldi10 conference in Warsaw, July 2013. The
contributed talks reported significant advances on various areas of research in
gravity.Comment: 15 pages. Contribution to the Proceedings of GR20 - Amaldi1
Natural Supergravity Inflation
We show that a single uncharged chiral superfield, canonically coupled to
\mbox{} supergravity with vanishing superpotential, naturally drives
inflation in the early universe for a class of simple Kahler potentials.
Inflation occurs due to the one-loop generation of a Kahler anomaly
proportional to . The coefficient of this term is of the correct
magnitude to describe all aspects of an inflationary cosmology, including
sufficient amplitude perturbations and reheating. Higher order terms
proportional to for are naturally suppressed relative to the
term and, hence, do not destabilize the theory.Comment: 13 pages, CERN-TH.6685/92, UPR-0526
Entropy Function for Heterotic Black Holes
We use the entropy function formalism to study the effect of the Gauss-Bonnet
term on the entropy of spherically symmetric extremal black holes in heterotic
string theory in four dimensions. Surprisingly the resulting entropy and the
near horizon metric, gauge field strengths and the axion-dilaton field are
identical to those obtained by Cardoso et. al. for a supersymmetric version of
the theory that contains Weyl tensor squared term instead of the Gauss-Bonnet
term. We also study the effect of holomorphic anomaly on the entropy using our
formalism. Again the resulting attractor equations for the axion-dilaton field
and the black hole entropy agree with the corresponding equations for the
supersymmetric version of the theory. These results suggest that there might be
a simpler description of supergravity with curvature squared terms in which we
supersymmetrize the Gauss-Bonnet term instead of the Weyl tensor squared term.Comment: LaTeX file, 23 pages; v2: references added; v3: minor addition; v4:
minor change
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