Related papers: UV Perturbations in Brane Gas Cosmology
We consider the evolution of cosmological perturbations during radion stabilization, which we assume to happen after a period of inflation in the early universe. Concentrating on the Randall-Sundrum brane world scenario, we find that if…
`Old' String Theory is a theory of one-dimensional extended objects, whose vibrations correspond to excitations of various target-space field modes including gravity. In these lectures I will give an introduction to low-energy Effective…
We consider the cosmological evolution of the three-brane in the background of type IIB string theory. For two different backgrounds which give nontrivial dilaton profile we have derived the Friedman-like equations. These give the…
We consider the case of a generic braneworld geometry in the presence of one or more moduli fields (e.g., the dilaton) that vary throughout the bulk spacetime. Working in an arbitrary conformal frame, using the generalized junction…
We argue that string theory has all the ingredients to provide us with candidates for the cold dark matter and explain the current acceleration of our Universe. In any generic string compactification the dilaton plays an important role as…
String effective theories contain a dilaton scalar field which couples to gravity, matter and radiation. In general, particle masses will have different dilaton couplings. We can always choose a conformal frame in which baryons have…
We study diffusion damping of acoustic waves in the photon-baryon fluid due to cosmic strings, and calculate the induced $\mu$- and $y$-type spectral distortions of the cosmic microwave background. For cosmic strings with tension within…
It is shown that a first-order cosmological perturbation theory for the open, flat and closed Friedmann-Lema\^itre-Robertson-Walker universes admits one, and only one, gauge-invariant variable which describes the perturbation to the energy…
We investigate the effects of cosmological expansion on the spectrum of small-scale structure on a cosmic string. We simulate the evolution of a string with two modes that differ in wavelength by one order of magnitude. Once the short mode…
We address the important issue of stabilizing the dilaton in the context of superstring cosmology. Scalar potentials which arise out of gaugino condensates in string models are generally exponential in nature. In a cosmological setting this…
Using a gauge-invariant formalism we derive and solve the perturbed cosmological equations for the BSBM theory of varying fine structure 'constant'. We calculate the time evolution of inhomogeneous perturbations of the fine structure…
We study the cosmological evolution of a D3-brane Universe in a type 0 string background. We follow the brane universe along the radial coordinate of the background and we calculate the energy density which is induced on the brane because…
The requirement that the laws of physics must be invariant under point-dependent transformations of the units of length, time, and mass is used as a selection principle while studying different generic effective theories of gravity. Thereof…
We investigate the possibility of embedding the vector curvaton paradigm in D-brane models of inflation in Type IIB string theory in a simple toy model. The vector curvaton is identified with the U(1) gauge field that lives on the world…
If the graviton possesses an arbitrarily small (but nonvanishing) mass, perturbation theory implies that cosmic strings have a nonzero Newtonian potential. Nevertheless in Einstein gravity, where the graviton is strictly massless, the…
String gas cosmology is a string theory-based approach to early universe cosmology which is based on making use of robust features of string theory such as the existence of new states and new symmetries. A first goal of string gas cosmology…
We investigate stability of single S-brane singular solutions obtained in our previous papers. A stable perturbative solution exists for each of them, while an unstable one exists only if the dilaton field does not depend on time. We apply…
The time evolution of thermal and thermo-reactive instabilities of primordial gas in the presence of ionizing UV radiation is studied. We obtain conditions (depending on density, temperature, and UV radiation intensity) favorable for the…
Using the linear multiplet formulation for the dilaton superfield, we construct an effective lagrangian for hidden-sector gaugino condensation in string effective field theories with arbitrary gauge groups and matter. Nonperturbative string…
This short note emphasises a potential tension between string models of inflation based on systems of branes and antibranes and the spectrum of strings in curved space, in particular the requirement that the leading Regge trajectory extends…