Related papers: The Stability of D-term Cosmic Strings
We consider a d-dimensional spherically symmetric dilatonic R^2 string corrected black hole solution. We study its stability under tensor type gravitational perturbations and compute the absorption cross section for low frequency…
Chiral cosmic strings naturally arise in many particle physics models, in particular in supersymmetric theories with a D-term. These strings have a single fermion zero mode in the core. We derive the general equation of motion for such…
We consider the static planar black hole solutions in the STU model of the gauged $\mathcal{N}=8$ supergravity in four dimensions. We give a straightforward derivation of the equation of state of the purely electric and purely magnetic…
We present a numerical solution of a stationary 5-dimensional spinning cosmic string in the Einstein-Yang-Mills (EYM) model, where the extra bulk coordinate $\psi$ is periodic. It turns out that when $g_{\psi\psi}$ approaches zero, i.e., a…
We consider conditions for existence and stability of a static cosmological solution in quadratic gravity. It appears that such a solution for a Universe filled by only one type of perfect fluid is possible in a wide range of the equation…
There are two important examples of physical systems which violate the strong energy condition : Universes (like, it would seem, our own) with a positive cosmological constant, and wormholes. We suggest that a positive cosmological constant…
We discuss the Freund-Rubin compactification with cosmological constant and the dilaton field, and examine the stability of the spacetimes at the low energy. The Minkowski or de Sitter spacetime can be obtained if the dilation field is…
In this paper, we analyze numerically the behaviour of the solutions corresponding to a non-Abelian cosmic string in the framework of the Starobinsky model, i.e. where $f(R)=R + \zeta R^2$. We perform the calculations for both an…
In this paper we undertake the modified theory of gravity f(R,T) where R and T are the Ricci scalar and the trace of the energy momentum tensor, respectively. Imposing the conservation of the energy momentum tensor, we obtain a model about…
We consider coupled gravitational and electromagnetic perturbations of a family of five-dimensional Einstein-Maxwell solutions that describes both magnetized black strings and horizonless topological stars. We find that the odd…
We elaborate on the cosmological implications of the recently established non-perturbative $O(D,D$)-symmetric approach. Following the $\alpha'$-complete Friedmann equations, we provide a qualitative description of the dynamics of anisotropy…
We consider cosmological solutions and their stability with respect to homogeneous and isotropic perturbations in the braneworld model with the scalar-curvature term in the action for the brane. Part of the results are similar to those…
We investigate the stability properties of an abstract class of semi-linear systems. Our main result establishes rational rates of decay for classical solutions assuming a certain non-uniform observability estimate for the linear part and…
We revisit the genuine Fayet-Iliopoulos terms of 4D N=1 supergravity. Such terms are commonly believed to preserve a global symmetry, and therefore they are in conflict with the principles of quantum gravity. However, we find that…
We discuss cosmic Nielsen-Olesen strings in space-times endowed with a positive cosmological constant. For the cylindrically symmetric, static free cosmic string, we discuss the contribution of the cosmological constant to the angle…
We review recent progress on the instabilities of black strings and branes both for pure Einstein gravity as well as supergravity theories which are relevant for string theory. We focus mainly on Gregory-Laflamme instabilities. In the first…
A field-theoretical model for non-singular global cosmic strings is presented. The model is a non-linear sigma model with a potential term for a self-gravitating complex scalar field. Non-singular stationary solutions with angular momentum…
We consider the low energy phenomenology of superstrings. In particular we analyse supersymmetry breaking via gaugino condensate and we compare the phenomenology of the two different approaches to stabilize the dilaton field. We study the…
The spectrum of $(p,q)$ bound states of F- and D-strings has a distinctive square-root tension formula that is hoped to be a hallmark of fundamental cosmic strings. We point out that the Bogomol'nyi-Prasad-Sommerfield (BPS) bound for…
We study a field theoretical model for p-q-superstrings in a fixed Anti-de-Sitter background. We find that the presence of the negative cosmological constant tends to decrease the core radius of the strings. Moreover, the binding energy…