Improved estimation of radiated axions from cosmological axionic strings

TL;DR

This paper presents advanced field-theoretic simulations of axionic string networks, providing more precise energy spectra and constraints on axion decay constants, with implications for early universe cosmology.

Contribution

It introduces a new efficient string identification scheme and a pseudo power spectrum estimator, improving the accuracy of axion emission estimates from cosmological strings.

Findings

Scaling parameter =0.87 b1 0.14 consistent with previous studies

More precise energy spectrum calculation reduces error in axion emission estimates

Constraint on axion decay constant f_a b1 3d7 10^{11} GeV

Abstract

Cosmological evolution of axionic string network is analyzed in terms of field-theoretic simulations in a box of 512^3 grids, which are the largest ever, using a new and more efficient identification scheme of global strings. The scaling parameter is found to be \xi=0.87 +- 0.14 in agreement with previous results. The energy spectrum is calculated precisely using a pseudo power spectrum estimator which significantly reduces the error in the mean reciprocal comoving momentum. The resultant constraint on the axion decay constant leads to f_a <= 3*10^11 GeV. We also discuss implications for the early Universe.