Related papers: Linear Perturbations in Brane Gas Cosmology
A global O$(2,2)$ symmetry is found in the Brans-Dicke theory of gravity when the dilaton is coupled to axion and moduli fields. The symmetry is broken if a cosmological constant is introduced. Within the class of spatially homogeneous…
We study the effect of the geometry and topology of a scalar-tensor cosmic string space-time on the electric and magnetic fields of line sources. It is shown that the dilatonic coupling of the gravity induces effects along the string…
In string theory the coupling ``constants'' appearing in the low-energy effective Lagrangian are determined by the vacuum expectation values of some (a priori) massless scalar fields (dilaton, moduli). This naturally leads one to expect a…
The perturbative modes propagating along an infinite string are investigated within the framework of the gauge invariant perturbation formalism on a spacetime containing a self-gravitating straight string with a finite thickness. These…
The stability conditions for coordinate gauge independent perturbations of brane-worlds are analyzed. It is shown that, these conditions lead to the Einstein-Hilbert dynamics and to a confined gauge potential, independently of models and…
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 discuss the main cosmological implications of considering string-loop effects and a potential for the dilaton in the lowest order string effective action. Our framework is based on the effective model arising from regarding homogeneous…
We present a critical review about the study of linear perturbations of matched spacetimes including gauge problems. We analyse the freedom introduced in the perturbed matching by the presence of background symmetries and revisit 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…
The supporting worldsheet of a string, membrane, or other higher dimensional brane, is analysed in terms of its first, second, and third fundamental tensors, and its inner and outer curvature tensors. The dynamical equations governing the…
We review the study of inhomogeneous perturbations about a homogeneous and isotropic background cosmology. We adopt a coordinate based approach, but give geometrical interpretations of metric perturbations in terms of the expansion, shear…
We consider linear perturbation equations for long-wavelength scalar metric perturbations in generalised gravity, applicable to non-singular cosmological models including a bounce from collapse to expansion in the very early universe. We…
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…
We compute spectra of particles produced during a dilaton-driven kinetic inflation phase within string cosmology models. The resulting spectra depend on the parameters of the model and on the type of particle and are quite varied, some…
We propose a mechanism for solving the horizon and entropy problems of standard cosmology which does not make use of cosmological inflation. Crucial ingredients of our scenario are brane gases, extra dimensions, and a confining potential…
We consider the theory obtained by adding to the usual string frame dilaton gravity action specially constructed higher derivative terms motivated by the limited curvature construction of [MukhanovET1992a] and determine the spatially…
String-loop effects may generate very weak matter couplings for a (massless) dilaton. We examine limits on the shift of such a dilaton toward its present equilibrium value from big-bang nucleosynthesis and the binary pulsar. On the other…
We investigate the nature of ordinary cosmic vortices in some scalar-tensor extensions of gravity. We find solutions for which the dilaton field condenses inside the vortex core. These solutions can be interpreted as raising the degeneracy…
The stability of the cosmological event horizons found recently by Gregory [Phys. Rev. D54, 4955 (1996)] for a class of non-static global cosmic strings is studied. It is shown that they are not stable to both test particles and physical…
It is presented an exact solution of straight spinning cosmic strings in Brans-Dicke theory of gravitation. The possibility of the existence of closed timelike curves around these cosmic strings is analyzed. Furthermore, the stability about…