Black Holes with Varying Flux: A Numerical Approach

We present a numerical study of type IIB supergravity solutions with varying Ramond-Ramond flux. We construct solutions that have a regular horizon and contain nontrivial five- and three-form fluxes. These solutions are holographically dual to the deconfined phase of confining field theories at finite temperature. As a calibration of the numerical method we first numerically reproduce various analytically known solutions including singular and regular nonextremal D3 branes, the Klebanov-Tseytlin solution and its singular nonextremal generalization. The horizon of the solutions we construct is of the precise form of nonextremal D3 branes. In the asymptotic region far away from the horizon we observe a logarithmic behavior similar to that of the Klebanov-Tseytlin solution.Comment: 40 pages, 15 figure

Primordial fluctuations and cosmological inflation after WMAP 1.0

The observational constraints on the primordial power spectrum have tightened considerably with the release of the first year analysis of the WMAP observations, especially when combined with the results from other CMB experiments and galaxy redshift surveys. These observations allow us to constrain the physics of cosmological inflation: (i) The data show that the Hubble distance is almost constant during inflation. While observable modes cross the Hubble scale, it changes by less than 3% during one e-folding: d(d_H)/dt < 0.032 at 2 sigma. The distance scale of inflation itself remains poorly constrained: 1.2 x 10^{-28} cm < d_H < 1 cm. (ii) We present a new classification of single-field inflationary scenarios (including scenarios beyond slow-roll inflation), based on physical criteria, namely the behaviour of the kinetic and total energy densities of the inflaton field. The current data show no preference for any of the scenarios. (iii) For the first time the slow-roll assumption could be dropped from the data analysis and replaced by the more general assumption that the Hubble scale is (almost) constant during the observable part of inflation. We present simple analytic expressions for the scalar and tensor power spectra for this very general class of inflation models and test their accuracy.Comment: 19 pages, 5 figures; section on the classification of models in the plane of tilt and tensor-to-scalar ratio added, references adde

Second Order General Slow-Roll Power Spectrum

Recent combined results from the Wilkinson Microwave Anisotropy Probe (WMAP) and Sloan Digital Sky Survey (SDSS) provide a remarkable set of data which requires more accurate and general investigation. Here we derive formulae for the power spectrum P(k) of the density perturbations produced during inflation in the general slow-roll approximation with second order corrections. Also, using the result, we derive the power spectrum in the standard slow-roll picture with previously unknown third order corrections.Comment: 11 pages, 1 figure ; A typo in Eq. (38) is fixed ; References expanded and a note adde

Black Holes in Cascading Theories: Confinement/Deconfinement Transition and other Thermal Properties

We present numerical evidence for a transition between the Klebanov-Strassler background and a solution describing a black hole in the class of cascading solutions in the chirally restored phase. We also present a number of properties of this solution, including the running of the coupling constant, the viscosity to entropy ratio and the drag force on a quark moving in this background.Comment: 34 pages, 7 figures. Version to be published by JHE

Brany Liouville Inflation

We present a specific model for cosmological inflation driven by the Liouville field in a non-critical supersymmetric string framework, in which the departure from criticality is due to open strings stretched between the two moving Type-II 5-branes. We use WMAP and other data on fluctuations in the cosmic microwave background to fix parameters of the model, such as the relative separation and velocity of the 5-branes, respecting also the constraints imposed by data on light propagation from distant gamma-ray bursters. The model also suggests a small, relaxing component in the present vacuum energy that may accommodate the breaking of supersymmetry.Comment: 23 pages LATEX, two eps figures incorporated; version accepted for publication in NJ