Related papers: Cosmic Superstrings Stabilized by Fermions

We present a construction of a perturbatively stable non-supersymmetric type II closed string model in four dimensions. It is based on a freely acting Scherk-Schwarz Z2-deformation of a supersymmetric construction which is recovered in…

Superstring models describing curved 4-dimensional magnetic flux tube backgrounds are exactly solvable in terms of free fields. We first consider the simplest model of this type (corresponding to `Kaluza-Klein' Melvin background). Its 2d…

A generic form of low-energy effective action of superstring theories with one-loop quantum correction is well known. Based on this action we derive the complete perturbation equations and general analytic solutions in the cosmological…

In flat space-time, sigma-model strings and textures are both unstable to collapse and subsequent decay. With sufficient cosmological expansion, however, they are stable in a generalized sense: a small perturbation will cause them to change…

We investigate the evolution of small perturbations around black strings and branes which are low energy solutions of string theory. For simplicity we focus attention on the zero charge case and show that there are unstable modes for a…

The existence and stability under linear perturbation of closed timelike curves in the spacetime associated to Schwarzschild black hole pierced by a spinning string are studied. Due to the superposition of the black hole, we find that the…

Cosmic (super)strings offer promising ways to test ideas about the early universe and physics at high energies. While in field theory constructions their tension is usually assumed to be constant (or at most slowly-varying), this is often…

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…

The dynamical evolution of superconducting cosmic string loops with specific equations of state describing timelike and spacelike currents is studied numerically. This analysis extends previous work in two directions: first it shows results…

There is evidence that string theory possesses a large discretuum of stable and/or metastable ground states, with zero or four supersymmetries in four dimensions. I discuss critically the nature of this evidence. Assuming this "landscape"…

We study the quantum energy of the Z-string in 2+1 dimensions using the phase shift formalism. Our main interest is the question of stability of a Z-string carrying a finite fermion number.

An interesting feature of some open superstring models in $D < 10$ is the simultaneous presence, in the spectrum, of gauge fields and of a number of antisymmetric tensor fields. In these cases the Green-Schwarz mechanism can (and does) take…

In this work we consider the evolution of a massive scalar field in cylindrically symmetric space-times. Quasinormal modes have been calculated for static and rotating cosmic cylinders. We found unstable modes in some cases. Rotating as…

We study the stability of cosmic string wakes against the disruption by the dominant Gaussian fluctuations which are present in cosmological models. We find that for a string tension given by $G \mu = 10^{-7}$ wakes remain locally stable…

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…

Progress on string theory in curved spacetimes since 1992 are reviewed. After a short introduction on strings in Minkowski and curved spacetimes, we focus on strings in cosmological spacetimes. The classical behaviour of strings in FRW and…

I present two interesting studies related to the role of solitons in theories with spontaneous symmetry breaking. Quantised fermions coupled to solitons are known to induce fractional fermion number. I present an example where an unstable…

This investigation is concerned with cosmological scenarios based on particle physics theories that give rise to superconducting cosmic strings (whose subsequent evolution may produce stable loop configurations known as vortons). Cases in…

We uncover a rich microphysical structure for SO(10) cosmic strings. For the abelian string the electroweak symmetry is restored around it in a region depending on the electroweak scale. A rich structure of nonabelian strings is found. Some…

The closed relativistic string carrying a point-like mass in the space with nontrivial geometry is considered. For rotational states of this system (resulting in non-trivial Regge trajectories) the stability problem is solved. It was shown…