Scaling laws for nonintercommuting cosmic string networks

Abstract

We study the evolution of non-interacting and entangled cosmic string networks in the context of the velocity-dependent one-scale model. Such networks may be formed in several contexts, including brane inflation. We show that the frozen network solution L ∝ a, although generic, is only a transient one, and that the asymptotic solution is still L ∝ t as in the case of ordinary (intercommuting) strings, although in the present context the universe will usually be string-dominated. Thus the behaviour of two strings when they cross does not seem to affect their scaling laws, but only their densities relative to the background.

Evolution of cosmic superstring networks: a numerical simulation

“…The fairly linear behaviour of l A is the main change. A linear fit to the evolution of l A gives 19) with α LA ≈ 0.8. Extrapolating this behaviour to large τ , we expect a scaling regime in which l A is a few times larger than ξ and ξ N .…”

“…These models allow for several types of string with different tensions and use the velocity-dependent one-scale model of string evolution [17,18] (see also [19]). The models make somewhat different assumptions about the physics of F -and D-string interaction.…”

Scaling properties of cosmic (super)string networks

“…We start by pointing out that explicit energy losses are not absolutely necessary for scaling in a cosmological context: the expansion itself may provide sufficient damping. For strings, scaling will occur for any expansion rate λ > 1/2, regardless of energy losses (Martins, 2004) for domain walls, the analogous threshold is λ > 1/4. Among other things this implies that for strings to scale in the matter era loop production not needed for scaling, as is known since the first generation of numerical simulations in the early 1990s.…”

“…• The role of the intercommuting probabilities, first considered in a simple way in Martins (2004) and then quantified using numerical simulations in Avgoustidis & Shellard (2006).…”

Deviation from ΛCDM with cosmic strings networks

“…But later on it was shown that in non-abelian string network, intercommutation may be prevented due to topological constraints and stable fraustrated network of strings may form [13]. More recent numerical simulations show that in the string dominated universe v 2 s ≤ 0.17 [25,26] and can never be exactly zero for nonintercommutating strings. In this case, the string network can never be conformally stretched to the Hubble scale preventing them to fraustrate.…”