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We study the behaviour of cosmic string networks in contracting universes, and discuss some of their possible consequences. We note that there is a fundamental time asymmetry between defect network evolution for an expanding universe and a…

Astrophysics · Physics 2009-11-07 P. P. Avelino , C. J. A. P. Martins , C. Santos , E. P. S. Shellard

Cosmic strings may have formed in the early universe due to the Kibble mechanism. While string networks are usually modeled as being of Nambu-Goto type, this description is understood to be a convenient approximation, which neglects the…

Cosmology and Nongalactic Astrophysics · Physics 2021-09-01 A. R. R. Almeida , C. J. A. P. Martins

We simulate the formation and the evolution of global strings taking into account the expansion of the universe and the concomitant change of the effective potential, that is, the change from the restoration stage of the global {\it…

High Energy Physics - Phenomenology · Physics 2009-10-31 Masahide Yamaguchi , Jun'ichi Yokoyama , M. Kawasaki

When moduli roll in the early universe, all physical scales - including string tensions - simultaneously evolve. The dynamics of cosmic string loops with time-varying tension can produce cosmic string loop trackers in which most of the…

High Energy Physics - Phenomenology · Physics 2025-11-21 Joseph P. Conlon , Edmund J. Copeland , Edward Hardy , Noelia Sánchez González

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…

Cosmology and Nongalactic Astrophysics · Physics 2018-12-03 C. J. A. P. Martins

We study the spectrum of loops as a part of a complete network of cosmic strings in flat spacetime. After a long transient regime, characterized by production of small loops at the scale of the initial conditions, it appears that a true…

General Relativity and Quantum Cosmology · Physics 2009-11-11 Vitaly Vanchurin , Ken D. Olum , Alexander Vilenkin

At its very beginning, the universe is believed to have grown exponentially in size via the mechanism of inflation. The almost scale-invariant density perturbation spectrum predicted by inflation is strongly supported by cosmological…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-23 David F. Chernoff , S. -H. Henry Tye

It is well known that the $\Lambda$-term is a very good candidate for the smooth component of the universe since it resolves the so-called ``$\Omega$-problem'' giving, at the same time, sufficiently large age of the universe. However, the…

Astrophysics · Physics 2009-10-28 Jerzy Stelmach

We describe a numerical simulation of the evolution of an $S_3$ cosmic string network which takes fully into account the non-commutative nature of the cosmic string fluxes and the topological obstructions which hinder strings from moving…

Astrophysics · Physics 2009-10-30 Patrick N. McGraw

We develop an analytic model to quantitatively describe the evolution of superconducting cosmic string networks. Specifically, we extend the velocity-dependent one-scale (VOS) model to incorporate arbitrary currents and charges on cosmic…

Cosmology and Nongalactic Astrophysics · Physics 2021-03-03 C. J. A. P. Martins , Patrick Peter , I. Yu. Rybak , E. P. S. Shellard

We study the behaviour and consequences of cosmic string networks in contracting universes. They approximately behave during the collapse phase as a radiation fluids. Scaling solutions describing this are derived and tested against…

Astrophysics · Physics 2015-06-24 P. P. Avelino , C. J. A. P. Martins , C. Santos , E. P. S. Shellard

We present results from a detailed numerical study of the small-scale and loop production properties of cosmic string networks, based on the largest and highest resolution string simulations to date. We investigate the non-trivial fractal…

Astrophysics · Physics 2008-11-26 C. J. A. P. Martins , E. P. S. Shellard

In this paper we find new scaling laws for the evolution of $p$-brane networks in $N+1$-dimensional Friedmann-Robertson-Walker universes in the weakly-interacting limit, giving particular emphasis to the case of cosmic superstrings ($p=1$)…

Cosmology and Nongalactic Astrophysics · Physics 2012-10-16 P. P. Avelino , L. Sousa

Prompted by the recent more precise determination of the basic cosmological parameters and growing evidence that the matter-energy content of the universe is now dominated by dark energy and dark matter we present the general solution of…

General Relativity and Quantum Cosmology · Physics 2009-11-11 Marek Demianski , Zdzislaw A. Golda , Andrzej Woszczyna

We study the approach to scaling in axion string networks in the radiation era, through measuring the root-mean-square velocity $v$ as well as the scaled mean string separation $x$. We find good evidence for a fixed point in the phase-space…

Cosmology and Nongalactic Astrophysics · Physics 2021-06-02 Mark Hindmarsh , Joanes Lizarraga , Asier Lopez-Eiguren , Jon Urrestilla

We found that models of evolving random networks exhibit dynamic scaling similar to scaling of growing surfaces. It is demonstrated by numerical simulations of two variants of the model in which nodes are added as well as removed [Phys.…

Statistical Mechanics · Physics 2009-11-07 Miroslav Kotrla , Frantisek Slanina , Jakub Steiner

Previously developed analytic models for the evolution of cosmic string and monopole networks are applied to networks of monopoles attached to two or more strings; the former case is usually known as cosmic necklaces. These networks are a…

High Energy Physics - Phenomenology · Physics 2014-11-21 C. J. A. P. Martins

Understanding of the signatures of cosmic string networks is limited by a large uncertainty in the sizes at which cosmic string loops form. We review cosmic string network evolution, and the gravitational signatures, with emphasis on this…

Astrophysics · Physics 2007-11-07 Joseph Polchinski

Using a new parallel computing technique, we have run the largest cosmic string simulations ever performed. Our results confirm the existence of a long transient period where a non-scaling distribution of small loops is produced at lengths…

Cosmology and Nongalactic Astrophysics · Physics 2015-03-18 Jose J. Blanco-Pillado , Ken D. Olum , Benjamin Shlaer

At early stages the dynamics of cosmic string networks is expected to be influenced by an excessive production of small loops at the scales of initial conditions l_{min}. To understand the late time behavior we propose a very simple…

High Energy Physics - Theory · Physics 2014-11-21 Vitaly Vanchurin