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Cosmic strings and other topological defects in nonscaling regimes

R. P. L. Azevedo, C. J. A. P. Martins


Cosmic strings are topological defects possibly formed in the early Universe, which may be observable due to their gravitational effects on the cosmic microwave background radiation or gravitational wave experiments. To this effect, it is important to quantitatively ascertain the network properties, including their density, velocity, or the number of strings present, at the various epochs in the observable Universe. Attempts to estimate these numbers often rely on simplistic approximations for the string parameters, such as assuming that the network is scaling. However, in cosmological models containing realistic amounts of radiation, matter, and dark energy, a string network is never exactly scaling. Here, we use the velocity-dependent one-scale model for the evolution of a string network to better quantify how these networks evolve. In particular, we obtain new approximate analytic solutions for the behavior of the network during the radiation-to-matter and matter-to-acceleration transitions (assuming, in the latter case, the canonical Λ cold dark matter model) and numerically calculate the relevant quantities for a range of possible dark energy models.


Physical Review D
Volume 95, Issue 4
2017 February

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Faculdade de Ciências da Universidade de Lisboa Universidade do Porto Faculdade de Ciências e Tecnologia da Universidade de Coimbra
Fundação para a Ciência e a Tecnologia COMPETE 2020 PORTUGAL 2020 União Europeia