Related papers: Topological Defects in Contracting Universes

In string theory, the traditional picture of a Universe that emerges from the inflation of a very small and highly curved space-time patch is a possibility, not a necessity: quite different initial conditions are possible, and not…

If the Universe underwent a cosmic phase transition, it may have left behind a network of cosmic strings. When these strings arise from the breaking of a gauge symmetry, their decay produces a significant stochastic background of…

In dilaton gravity theories, we consider a string-like topological defect formed during U(1) gauge symmetry-breaking phase transition in the early Universe, and far from the cosmic string we have vacuum solutions of the generalized Einstein…

Many symmetry breaking patterns in grand unified theories (GUTs) give rise to cosmic strings that eventually decay when pairs of GUT monopoles spontaneously nucleate along the string cores. These strings are known as metastable cosmic…

The spectrum of stable electrically and magnetically charged supersymmetric particles can change discontinuously due to the decay of these particles as the vacuum on the Coulomb branch is varied. We show that this decay process is well…

From a classical analysis, we show that gravitational waves in a cosmological medium with equation of state $\omega=-1/3$ can follow a London-like equation, implying that some gravitational wave solutions present a decay for certain…

Whilst standard field theoretic Cosmic Strings cannot end, Cosmic Superstrings can form three string junctions, at which each string ends. This opens up a new class of possible boundary conditions for such strings and we show that, at least…

The evolution of the spectrum of cosmological fluctuations from one cycle to the next is studied. It is pointed out that each cycle leads to a reddening of the spectrum. This opens up new ways to generate a scale-invariant spectrum of…

The formalism for computing the gravitational power radiation from excitations on cosmic strings forming a junction is presented and applied to the simple case of co-planar strings at a junction when the excitations are generated along one…

We argue that in the context of string theory a large number N of connected degenerate vacua that mix will lead to a ground state with much lower energy, essentially because of the standard level repulsion of quantum theory for the…

We present the results of a field theory simulation of networks of strings in the Abelian Higgs model. Starting from a random initial configuration we show that the resulting vortex tangle approaches a self-similar regime in which the…

The decay of the string perturbative vacuum into our present cosmological state is associated to the transition from a phase of growing curvature and growing dilaton, to a phase of decreasing curvature and frozen dilaton. The possible…

We argue that the light particles in string theory obey an effective quantum mechanics modified by the inclusion of a quantum-gravitational friction term, induced by unavoidable couplings to unobserved massive string states in the…

Topological defects in the framework of effective quantum gravity model are investigated, based on the hypothesis of an effective fractal dimension of the universe. This is done by using Caputo fractional derivatives to determine the…

It has been claimed that the string landscape predicts an open universe, with negative curvature. The prediction is a consequence of a large number of metastable string vacua, and the properties of the Coleman--De Luccia instanton which…

Some of the phenomenological implications of string cosmological models are reviewed, with particular attention to the spectra of the tensor, scalar and vector modes of the geometry. A class of self-dual string cosmological models is…

The possibility to detect cosmic strings -- topological defects of early Universe, by means of wave effects in gravitational lensing is discussed. To find the optimal observation conditions, we define the hyperbolic-shaped Fresnel…

The properties of string networks at scales well below the horizon are poorly understood, but they enter critically into many observables. We argue that in some regimes, stretching will be the only relevant process governing the evolution.…

There has been recent interest in the evolution and cosmological consequences of global axionic string networks, and in particular in the issue of whether or not these networks reach the scale-invariant scaling solution that is known to…

Cosmic string networks generate cosmological perturbations actively throughout the history of the universe. Thus, the string sourced anisotropy of the cosmic microwave background is not affected by Silk damping as much as the anisotropy…