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Centro de Astrofísica da Universidade do Porto

Stochastic gravitational wave background generated by cosmic string networks: Velocity-dependent one-scale model versus scale-invariant evolution

L. Sousa, P. P. Avelino

Abstract
We compute the power spectrum of the stochastic gravitational wave background generated by cosmic string networks, described by the velocity-dependent one-scale (VOS) model for a wide range of macroscopic and microscopic parameters. The VOS model—which has been shown to provide an accurate macroscopic description of the evolution of cosmic string networks—is used to demonstrate that cosmic string networks are unable to rapidly attain scale-invariant evolution after the transition between the radiation and matter eras. However, in computations of the stochastic gravitational wave background, it is often assumed that the networks experience scale-invariant evolution throughout cosmological history. We demonstrate that this assumption leads to an underestimation of the amplitude and broadness of the peak of the spectrum. As a result, the total energy density of gravitational waves at the present day obtained using the VOS model may be up to 70% larger than that obtained under the linear scaling assumption.

Physical Review D
Volume 88
July 2013

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Institute of Astrophysics and Space Sciences (IA) is a new but long anticipated research infrastructure with a national dimension. It embodies a bold but feasible vision for the development of Astronomy, Astrophysics and Space Sciences in Portugal, taking full advantage and fully realizing the potential created by the national membership of the European Space Agency (ESA) and the European Southern Observatory (ESO). IA resulted from the merging the two most prominent research units in the field in Portugal: the Centre for Astrophysics of the University of Porto (CAUP) and the Center for Astronomy and Astrophysics of the University of Lisbon (CAAUL). It currently hosts more than two-thirds of all active researchers working in Space Sciences in Portugal, and is responsible for an even greater fraction of the national productivity in international ISI journals in the area of Space Sciences. This is the scientific area with the highest relative impact factor (1.65 times above the international average) and the field with the highest average number of citations per article for Portugal.

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