[Paper Review] On the evolution of abelian-Higgs string networks

J. N. Moore, E. P. S. Shellard|ArXiv.org|Aug 16, 1998

Cosmology and Gravitation Theories4 citations

TL;DR

This paper investigates the evolution of abelian-Higgs string networks via numerical simulations and compares them to a modified velocity-dependent one-scale model that includes loop production, massive radiation, and friction. The results show that loop production dominates network scaling, and massive radiation emission decays with wavelength, providing no strong evidence to reject the standard loop-based decay mechanism over direct massive radiation as the primary energy loss channel.

ABSTRACT

We study the evolution of abelian-Higgs string networks in numerical simulations. These are compared against a modified velocity-dependent one scale model for cosmic string network evolution. This incorporates the contributions of loop production, massive radiation and friction to the energy loss processes that are required for scaling evolution. We find that the loop distribution statistics in the simulations are consistent with the long-time scaling of the network being dominated by loop production. For an oscillating sinusoidal perturbation, we also demonstrate that the power emitted into massive radiation decays strongly with wavelength. Putting these observations together and extrapolating, we believe there is insufficient evidence to reject the the standard picture of string network evolution in favour of one where direct massive radiation is the dominant decay mechanism, a proposal which has attracted much recent interest.

Motivation & Objective

• To understand the long-term evolution of abelian-Higgs string networks in cosmological settings.
• To test whether direct massive radiation emission could dominate energy loss over loop production in cosmic string networks.
• To evaluate the validity of the standard loop-based decay mechanism against alternative models where massive radiation is the primary decay channel.
• To compare simulation results with a modified velocity-dependent one-scale model incorporating loop production, massive radiation, and friction.

Proposed method

• Numerical simulations of abelian-Higgs string networks are performed to track network evolution over time.
• A modified velocity-dependent one-scale model is used, which includes contributions from loop production, massive radiation, and friction for energy loss.
• The loop distribution statistics from simulations are analyzed to determine whether loop production dominates scaling behavior.
• The power emitted into massive radiation is computed for oscillating sinusoidal perturbations to assess its wavelength dependence.
• The results are extrapolated to evaluate whether massive radiation could be the dominant decay mechanism.
• Comparisons are made between simulation outcomes and theoretical predictions of the modified model to test consistency.

Experimental results

Research questions

• RQ1 Does loop production dominate the long-term scaling behavior of abelian-Higgs string networks in simulations?
• RQ2 How does the power emitted into massive radiation depend on the wavelength of string oscillations?
• RQ3 Is there sufficient evidence from simulations to reject the standard loop-based decay mechanism in favor of direct massive radiation as the dominant energy loss process?
• RQ4 To what extent do friction and massive radiation contribute to energy loss in the network evolution?
• RQ5 Can the modified velocity-dependent one-scale model accurately describe the observed network dynamics?

Key findings

• The loop distribution statistics in the simulations are consistent with the network scaling being dominated by loop production over long timescales.
• For an oscillating sinusoidal perturbation, the power emitted into massive radiation decays strongly with increasing wavelength.
• The observed emission of massive radiation is too weak to support the hypothesis that it is the dominant energy loss mechanism in cosmic string networks.
• The simulations show good agreement with the modified velocity-dependent one-scale model that includes loop production, friction, and massive radiation effects.
• Extrapolation of results suggests there is insufficient evidence to reject the standard picture of string network evolution in favor of a model where direct massive radiation dominates.
• The study finds no compelling support for the recent proposal that direct massive radiation is the primary decay channel for cosmic strings.