Search results for "General Relativity"
showing 10 items of 1057 documents
"Table 9" of "Search for Massive Colored Scalars in Four-Jet Final States in sqrt{s}=7 TeV proton-proton collisions with the ATLAS Detector"
1970
The observed 95% CL upper bounds on scalar pair production cross-section as a function of the scalar particle mass.
"Table 1" of "Search for Quantum Black-Hole Production in High-Invariant-Mass Lepton+Jet Final States Using Proton-Proton Collisions at sqrt(s) = 8 T…
2014
The combined 95% CL upper limits on the cross section times branching fraction (SIG*BR) for Quantum Black Holes decaying to a lepton and jet, as a function of the threshold mass, Mth.
The Regularized Hadamard Expansion
2017
A local expansion is proposed for two-point distributions involving an ultraviolet regularization in a four-dimensional globally hyperbolic space-time. The regularization is described by an infinite number of functions which can be computed iteratively by solving transport equations along null geodesics. We show that the Cauchy evolution preserves the regularized Hadamard structure. The resulting regularized Hadamard expansion gives detailed and explicit information on the global dynamics of the regularization effects.
Inflating an inhomogeneous universe
2014
While cosmological inflation can erase primordial inhomogeneities, it is possible that inflation may not begin in a significantly inhomogeneous universe. This issue is particularly pressing in multifield scenarios, where even the homogeneous dynamics may depend sensitively on the initial configuration. This paper presents an initial survey of the onset of inflation in multifield models, via qualitative lattice-based simulations that do not include local gravitational backreaction. Using hybrid inflation as a test model, our results suggest that small subhorizon inhomogeneities do play a key role in determining whether inflation begins in multifield scenarios. Interestingly, some configurati…
Dark matter from gravitational particle production at reheating
2015
We show that curvature induced particle production at reheating generates adiabatic dark matter if there are non-minimally coupled spectator scalars weakly coupled to visible matter. The observed dark matter abundance implies an upper bound on spectator masses $m$ and non-minimal coupling values $\xi$. For example, assuming quadratic inflation, instant reheating and a single spectator scalar with only gravitational couplings, the observed dark matter abundance is obtained for $m\sim 0.1$ GeV and $\xi \sim 1$. Larger mass and coupling values of the spectator are excluded as they would lead to overproduction of dark matter.
Cascading dust inflation in Born-Infeld gravity
2015
In the framework of Born-Infeld inspired gravity theories, which deviates from General Relativity (GR) in the high curvature regime, we discuss the viability of Cosmic Inflation without scalar fields. For energy densities higher than the new mass scale of the theory, a gravitating dust component is shown to generically induce an accelerated expansion of the Universe. Within such a simple scenario, inflation gracefully exits when the GR regime is recovered, but the Universe would remain matter dominated. In order to implement a reheating era after inflation, we then consider inflation to be driven by a mixture of unstable dust species decaying into radiation. Because the speed of sound gravi…
Induced-Gravity Inflation in Supergravity Confronted with Planck2013 and BICEP2
2015
Supersymmetric versions of induced-gravity inflation are f ormulated within Super- gravity (SUGRA) employing two gauge singlet chiral superfie lds. The proposed superpotential is uniquely determined by applying a continuous R and a discrete Z2 symmetry. We also employ a logarithmic Kahler potential respecting the symmetries above and including all the allowed terms up to fourth order in powers of the various fields. When the Kahle r manifold exhibits a no-scale-type symmetry, the model predicts spectral index ns ≃ 0.963 and tensor-to-scalar r ≃ 0.004. Beyond no-scale SUGRA, ns and r depend crucially on the coefficient kSΦ involved in the fourth order term, which mixes the inflaton Φ with th…
Harrison-Zel'dovich primordial spectrum is consistent with observations
2010
Inflation predicts primordial scalar perturbations with a nearly scale-invariant spectrum and a spectral index approximately unity (the Harrison--Zel'dovich (HZ) spectrum). The first important step for inflationary cosmology is to check the consistency of the HZ primordial spectrum with current observations. Recent analyses have claimed that a HZ primordial spectrum is excluded at more than 99% c.l.. Here we show that the HZ spectrum is only marginally disfavored if one considers a more general reionization scenario. Data from the Planck mission will settle the issue.
Gravity waves from non-minimal quadratic inflation
2015
We discuss non-minimal quadratic inflation in supersymmetric (SUSY) and non-SUSY models which entails a linear coupling of the inflaton to gravity. Imposing a lower bound on the parameter cR, involved in the coupling between the inflaton and the Ricci scalar curvature, inflation can be attained even for subplanckian values of the inflaton while the corresponding effective theory respects the perturbative unitarity up to the Planck scale. Working in the non-SUSY context we also consider radiative corrections to the inflationary potential due to a possible coupling of the inflaton to bosons or fermions. We find ranges of the parameters, depending mildly on the renormalization scale, with adju…
From hybrid to quadratic inflation with high-scale supersymmetry breaking
2014
Motivated by the reported discovery of inflationary gravity waves by the BICEP2 experiment, we propose an inflationary scenario in supergravity, based on the standard superpotential used in hybrid inflation. The new model yields a tensor-to-scalar ratio r ~ 0.14 and scalar spectral index ns ~ 0.964, corresponding to quadratic (chaotic) inflation. The important new ingredients are the high-scale, (1.6-10) x 10^13 GeV, soft supersymmetry breaking mass for the gauge singlet inflaton field and a shift symmetry imposed on the K\"ahler potential. The end of inflation is accompanied, as in the earlier hybrid inflation models, by the breaking of a gauge symmetry at (1.2-7.1) x 10^16 GeV, comparable…