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Cosmic string networks are the best motivated relics of cosmological phase transitions, being unavoidable in many physically plausible extensions of the Standard Model. Most studies, including those providing constraints from and forecasts…

High Energy Physics - Phenomenology · Physics 2024-06-07 F. C. N. Q. Pimenta , C. J. A. P. Martins

We use the Velocity-dependent One Scale Model for topological defect evolution to explore and classify the possible scaling solutions for string networks with time-varying tension, in cosmological and non-cosmological settings and under two…

High Energy Physics - Phenomenology · Physics 2026-02-24 C. S. C. M. Coelho , A. -L. Y. Gschrey , C. J. A. P. Martins

Cosmic strings are topological defects arising in a variety of cosmological scenarios, as the Universe undergoes symmetry-breaking phase transitions, whose discovery would offer valuable insight into the high-energy physics that shaped the…

High Energy Physics - Phenomenology · Physics 2026-02-27 P. B. Barbosa , C. J. A. P. Martins

We apply a recently developed formalism to study the evolution of a current-carrying string network under the simple but generic assumption of a linear equation of state. We demonstrate that the existence of a scaling solution with…

Cosmology and Nongalactic Astrophysics · Physics 2021-11-24 C. J. A. P. Martins , Patrick Peter , I. Yu. Rybak , E. P. S. Shellard

We continue our exploration of the wiggly generalisation of the Velocity-Dependent One Scale Model for cosmic strings, through the study of its allowed asymptotic scaling solutions. We extend the work of a previous paper [Almeida $\&$…

Cosmology and Nongalactic Astrophysics · Physics 2022-11-09 A. Almeida , C. J. A. P. Martins

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 provide a general overview of the velocity-dependent one-scale model for cosmic string evolution and discuss two further extensions to it. We introduce and justify a new ansatz for the momentum parameter $k$, and also incorporate the…

High Energy Physics - Phenomenology · Physics 2014-11-17 C. J. A. P. Martins , E. P. S. Shellard

Cosmic strings with degrees of freedom beyond the standard Abrikosov-Nielsen-Olesen or Nambu-Goto strings are ubiquitous in field theory as well as in models with extra dimensions, such as string theoretic brane inflation scenarios. Here we…

High Energy Physics - Phenomenology · Physics 2015-06-03 M. F. Oliveira , A. Avgoustidis , C. J. A. P. Martins

We develop velocity-dependent models describing the evolution of string networks that involve several types of interacting strings, each with a different tension. These incorporate the formation of Y-type junctions with links stretching…

Astrophysics · Physics 2014-11-18 A. Avgoustidis , E. P. S. Shellard

We make use of the formalism described in a previous paper [Martins {\it et al.} Phys. Rev. D90 (2014) 043518] to address general features of wiggly cosmic string evolution. In particular, we highlight the important role played by poorly…

Cosmology and Nongalactic Astrophysics · Physics 2016-11-21 J. P. P. Vieira , C. J. A. P. Martins , E. P. S. Shellard

Cosmic string networks form during cosmological phase transitions as a consequence of the Kibble mechanism. The evolution of the simplest networks is accurately described by the canonical Velocity Dependent One-Scale (VOS) model. However,…

Cosmology and Nongalactic Astrophysics · Physics 2022-10-18 A. R. R. Almeida , C. J. A. P. Martins

We present concrete solutions with accelerated expansion in string theory, requiring a small, tractable list of stress energy sources. We explain how this construction (and others in progress) evades previous no go theorems for simple…

High Energy Physics - Theory · Physics 2014-12-09 Matthew Dodelson , Xi Dong , Eva Silverstein , Gonzalo Torroba

We discuss the cosmological evolution of cosmic strings with time-dependent tension. We show that, in the case that the tension changes as a power of time, the cosmic string network obeys the scaling solution: the characteristic scale of…

High Energy Physics - Phenomenology · Physics 2009-11-11 Masahide Yamaguchi

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 present an extension of the velocity-dependent one-scale model for cosmic string evolution, which is suitable for describing the evolution of local and global monopole networks. We discuss the key dynamical features that need to be…

High Energy Physics - Phenomenology · Physics 2009-11-13 C. J. A. P. Martins , A. Achucarro

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

Understanding the evolution and cosmological consequences of topological defect networks requires a combination of analytic modeling and numerical simulations. The canonical analytic model for defect network evolution is the…

Cosmology and Nongalactic Astrophysics · Physics 2020-01-08 J. R. C. C. C. Correia , C. J. A. P. Martins

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

The velocity-dependent `one-scale' model of Martins and Shellard is used to study the evolution of a cosmic string network (and the corresponding loop population) in open universes. It is shown that in this case there is no linear scaling…

Astrophysics · Physics 2009-10-30 C. J. A. P. Martins

The canonical velocity-dependent one-scale (VOS) model for cosmic string evolution must be calibrated using high resolution numerical simulations, We exploit our state of the art graphics processing unit accelerated implementation of the…

Cosmology and Nongalactic Astrophysics · Physics 2021-09-22 J. R. C. C. C. Correia , C. J. A. P. Martins
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