Related papers: String Quantum Gravity, Lorentz-Invariance Violati…

Overall, brane inflation is compatible with the recent analysis of the WMAP data. Here we explore the constraints of WMAP and 2dFGRS data on the various brane inflationary scenarios. Brane inflation naturally ends with the production of…

Recently, Kostelecky [V.A. Kostelecky, Phys. Lett. B 701, 137 (2011)] proposed that the spontaneous Lorentz invariance violation (sLIV) is related to Finsler geometry. Finsler spacetime is intrinsically anisotropic and induces naturally…

A cornerstone of special relativity is Lorentz Invariance, the postulate that all observers measure exactly the same photon speeds independently on the photon energies. However, a hypothesized structure of spacetime may alter this…

We describe the behavior of 5-dimensional black strings, subject to the Gregory-Laflamme instability. Beyond the linear level, the evolving strings exhibit a rich dynamics, where at intermediate stages the horizon can be described as a…

Astronomical observations of distant quasars may be important to test models for quantum gravity, which posit Planck-scale spatial uncertainties ('spacetime foam') that would produce phase fluctuations in the wavefront of radiation emitted…

We explore the possibility that our universe's current accelerated expansion is explained by a quintessence model with an exponential scalar potential, $V =V_0\, e^{-\lambda\, \phi}$, keeping an eye towards $\lambda \geq \sqrt{2}$ and an…

In this paper we study fermion perturbations in four dimensional black holes of string theory, obtained either from a non-extreme configuration of three intersecting five-branes with a boost along the common string or from a non-extreme…

In this paper we consider an inflating universe with long straight cosmic string along z-axis. We show that the effect of cosmic string can be taken as a perturbation on the background of FRW metric. Then by doing cosmological perturbations…

We study in some detail the master equation, and its solution in a simplified case modelling flavour oscillations of a two-level system, stemming from the Liouville-string approach to quantum space time foam. In this framework we discuss…

I make a novel contact between string theory and degenerate fermion dynamics in thin semiconductors. Utilizing AdS/CFT correspondence in string theory and tunability of coupling parameters in condensed matter systems, I focus on the…

We calculate the contribution of cosmic strings arising from a phase transition in the early universe, or cosmic superstrings arising from brane inflation, to the cosmic 21 cm power spectrum at redshifts z > 30. Future experiments can…

One of the most interesting predictions of string-inspired cosmological models is the presence of a stochastic background of relic gravitational waves in the frequency band accessible to Earth-based detectors. Here we consider a ``minimal''…

The observable universe could be a 1+3-surface (the "brane") embedded in a 1+3+\textit{d}-dimensional spacetime (the "bulk"), with Standard Model particles and fields trapped on the brane while gravity is free to access the bulk. At least…

It has recently been pointed out that generic models of quantum gravity must contend with severe phenomenological constraints imposed by gravitational Cerenkov radiation, neutrino oscillations and the cosmic microwave background radiation.…

I review some aspects of non-critical strings in connection with Lorentz-Invariance violating approaches to quantum gravity. I also argue how non-critical strings may provide a unifying framework where string Cosmology and quantum gravity…

The most important problem of fundamental Physics is the quantization of the gravitational field. A main difficulty is the lack of available experimental tests that discriminate among the theories proposed to quantize gravity. Recently,…

String cosmology models predict a relic background of gravitational-wave (GW) radiation in the early universe. The GW energy spectrum of radiated power increases rapidly with the frequency, and therefore it becomes a potential and…

Fast variations of gamma-ray flux from Active Galactic Nuclei and Gamma-Ray Bursts can constrain Lorentz Invariance Violation (LIV) because of the delayed (or advanced) arrival of photons with higher energies: this approach has lead to the…

We discuss cosmology in the context of Liouville strings, characterized by a central-charge deficit Q^2, in which target time is identified with (the world-sheet zero mode of the) Liouville field: Q-Cosmology. We use a specific example of…

Braneworld gravity is a model that endows physical space with an extra dimension. In the type II Randall-Sundrum braneworld gravity model, the extra dimension modifies the spacetime geometry around black holes, and changes predictions for…