@Article{Figueroa_etal2020,
author="Figueroa, D. G.
and Hindmarsh, M.
and Lizarraga, J.
and Urrestilla, J.",
title="Irreducible background of gravitational waves from a cosmic defect network: Update and comparison of numerical techniques",
journal="Physical Review D",
year="2020",
publisher="Amer Physical Soc",
volume="102",
number="10",
pages="103516--25pp",
abstract="Cosmological phase transitions in the early Universe may produce relics in the form of a network of cosmic defects. Independently of the order of a phase transition, topology of the defects, and their global or gauge nature, the defects are expected to emit gravitational waves (GWs) as the network energy-momentum tensor adapts itself to maintaining scaling. We show that the evolution of any defect network (and for that matter any scaling source) emits a GW background with spectrum Omega(GW) proportional to f(3) for f << f(0), Omega(GW) proportional to 1/f(2) for f(0) less than or similar to f less than or similar to feq, and Omega(GW) proportional to const (i.e., exactly scale invariant) for f >> f(eq), where f(0) and f(eq) denote respectively the frequencies corresponding to the present and matter-radiation equality horizons. This background represents an irreducible emission of GWs from any scaling network of cosmic defects, with its amplitude characterized only by the symmetry-breaking scale and the nature of the defects. Using classical lattice simulations we calculate the GW signal emitted by defects created after the breaking of a global symmetry O(N) -> O(N -- 1). We obtain the GW spectrum for N between 2 and 20 with two different techniques: integrating over unequal-time correlators of the energy-momentum tensor, updating our previous work on smaller lattices, and for the first time, comparing the result with the real-time evolution of the tensor perturbations sourced by the same defects. Our results validate the equivalence of the two techniques. Using cosmic microwave background upper bounds on the defects{\textquoteright} energy scale, we discuss the difficulty of detecting this GW background in the case of global defects.",
optnote="WOS:000589181600006",
optnote="exported from refbase (https://references.ific.uv.es/refbase/show.php?record=4618), last updated on Sun, 06 Dec 2020 17:03:37 +0000",
issn="2470-0010",
doi="10.1103/PhysRevD.102.103516",
opturl="https://arxiv.org/abs/2007.03337",
opturl="https://doi.org/10.1103/PhysRevD.102.103516",
language="English"
}