Cosmic string loops in the expanding universe

Abstract

We study the production of loops in the cosmic string network in the expanding background by means of a numerical simulation exact in the flat-spacetime limit and first-order in the expansion rate. We find an initial regime characterized by production of small loops at the scale of the initial correlation length, but later we see the emergence of a scaling regime of loop production. This qualitatively agrees with earlier expectations derived from the results of flat-spacetime simulations.In the final scaling regime we find that the characteristic length of loops scales as ∼ 0.1t in both radiation and matter eras.

Discrete gauge symmetry and Aharonov-Bohm radiation in string theory

“…This is the maximum size of the loops. According to the recent computer simulations of string networks [54][55][56], the typical initial size of the loops is governed by the cosmic time t when they are produced, L max αt with α ∼ 0.1. The parameter ξ is also determined by dynamics of cosmic string network.…”

Ultrahigh energy neutrinos from superconducting cosmic strings

“…Here and below we assume that the loop length parameter in (4) is α ∼ 0.1, as suggested by simulations [45,46]. Loops of the minimum length are of most importance in our calculations because they are the most numerous.…”

“…This issue has been a subject of much recent debate, with different simulations [43][44][45][46] and analytic studies [47,48] yielding different answers. Here we shall adopt the picture suggested by the largest and, in our view, the most accurate simulations of string evolution performed to date [45,46]. According to this picture, the characteristic length of loops formed at cosmic time t is given by the scaling relation…”

Radiation of supersymmetric particles from Aharonov-Bohm R-string

“…According to the recent computer simulations of string networks [35][36][37], the largest size of loops is given by L max ≃ αt with α ∼ 0.1.ṅ(t) is the number density of radiated particles per time and k/L is a typical momentum of radiated particles from the k-th Fourier mode. 6 It is worthy emphasizing that from the formula, β ≡ Kmax k 1 k ≃ log K max , we find that contribution from each mode to the number density per unit time is the same order and does not strongly depends on K max .…”