We study classical supertube probes on supergravity backgrounds which are sourced by over-rotating supertubes, and which therefore contain closed timelike curves. We show that the BPS probes are stable despite the appearance of negative kinetic terms in the probe action. By studying the radial oscillations of these probes, we show that closed geodesics exist on these backgrounds. email address:...

An overview is presented of possible cosmologically distant sources of gravitational wave backgrounds, especially those which might produce detectable backgrounds in the LISA band between 0.1 and 100 mHz. Examples considered here include inflation-amplified vacuum fluctuations in inflaton and graviton fields, bubble collisions in first-order phase transitions, Goldstone modes of classical self-...

the evidence suggests that emotional relationship with the opposite sex has been extended and a large group of juvenile's have experienced social relationships with the opposite sex. the basic problem of study is that how juveniles experienced consequences the relationship with the opposite sex on live? and are consequences the relationship with the opposite sex different or similarity amo...

We study giant graviton probes in the framework of the three–parameter deformation of the AdS5 × S background. We examine both the case when the brane expands in the deformed S̃ part of the geometry and the case when it blows up into AdS5. Performing a detailed analysis of small fluctuations around the giants, the configurations turn out to be stable. Our results hold even for the supersymmetric...

Here we discuss the two dimensional quantum electrodynamics in curved spacetime, especially in the background of some black holes. We first show the existence of some new quantum mechanical solution which has interesting properties. Then for some special black holes we discuss the fermion-black hole scattering problem. The issue of confinement is intimately connected with these solutions and we...

We describe a large class of exact string backgrounds with a null Killing vector arising, via a limiting à la Penrose procedure, from string backgrounds corresponding to coset conformal field theories for compact groups GN/HN times a free time-like boson U(1)−N . In this way a class of novel logarithmic conformal field theories (LCFT) emerges, that includes the one constructed recently as an N ...

We present the main features of the solution of the gravitino and dilatino Killing spinor equations derived in hep-th/0510176 and hep-th/0703143 which have led to the classification of geometric types of all type I backgrounds. We then apply these results to the supersymmetric backgrounds of the heterotic string. In particular, we solve the gaugino Killing spinor equation together with the othe...

Axions are a theoretically promising dark matter (DM) candidate. In the presence of radiation from bright astrophysical sources at radio frequencies, nonrelativistic DM axions can undergo stimulated decay to two nearly back-to-back photons, meaning that waves will have counterimage ("gegenschein") in exact opposite spatial direction. The be spectrally distinct backgrounds, taking form narrow li...

We compute the entanglement entropy, mutual information and quantum discord of Cosmic Microwave Background (CMB) fluctuations in real space. To that end, we first show measurements these at two distinct spatial locations can be described by a bipartite, continuous Gaussian system. This leads to explicit formulas for terms Fourier-space power spectra curvature perturbation. then find entanglemen...