Improved estimation of radiated axions from cosmological axionic strings
Abstract
Cosmological evolution of axionic string network is analyzed in terms of field-theoretic simulations in a box of 5123 grids, which are the largest ever, using a new and more efficient identification scheme of global strings. The scaling parameter is found to be =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 fa <= 3*1011 GeV. We also discuss implications for the early Universe.
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