Self-field of a moving string
Abstract
We discuss the effectiveness of the recently proposed quantity Js in suppressing the contribution of a string's self-field to its spectrum, which is used in field theory simulations to track the emission of axions by decaying cosmic strings. We compute the contribution of the self-field to the spectrum of this quantity and to the usually computed spectrum of ϕ∂tα for an infinitely long straight string. Although we demonstrate that the Js approach is a substantial improvement, we also point out that this highly symmetric model doesn't capture the full contribution of the self-field to the spectrum emitted by strings of a more complex shape, which are typical in network simulations. We then illustrate this point numerically using a simulation of a sinusoidally perturbed straight string. For this simple configuration, we managed to separate the contribution from the self-field and the radiation to the spectrum of Js, using the self-field subtraction method. This allows us to show that the spectrum of Js is still dominated by the n=1 mode of the string's oscillation, which can be attributed to the self-field and is largely suppressed when the self-field is removed. We also demonstrate that this mode is predominantly sourced by variations along the direction parallel to the string, which is missing in the unconnected segment model, used by arXiv:2512.13653 to claim the effectiveness of Js in suppressing the self-field's contribution to the spectrum.
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BibTeX
@misc{battye2026selffield,
title = {{Self-field of a moving string}},
author = {Richard A. Battye and Lukasz P. Bunio and Steven J. Cotterill},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.15366},
eprint = {2609.15366},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.15366},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Self-field of a moving string
AU - Richard A. Battye
AU - Lukasz P. Bunio
AU - Steven J. Cotterill
PY - 2026
DA - 2026/09/14
PB - arXiv
DO - 10.48550/arxiv.2609.15366
UR - https://arxiv.org/abs/2609.15366
AB - We discuss the effectiveness of the recently proposed quantity J_s in suppressing the contribution of a string's self-field to its spectrum, which is used in field theory simulations to track the emission of axions by decaying cosmic strings. We compute the contribution of the self-field to the spectrum of this quantity and to the usually computed spectrum of ϕ∂_tα for an infinitely long straight string. Although we demonstrate that the J_s approach is a substantial improvement, we also point out that this highly symmetric model doesn't capture the full contribution of the self-field to the spectrum emitted by strings of a more complex shape, which are typical in network simulations. We then illustrate this point numerically using a simulation of a sinusoidally perturbed straight string. For this simple configuration, we managed to separate the contribution from the self-field and the radiation to the spectrum of J_s, using the self-field subtraction method. This allows us to show that the spectrum of J_s is still dominated by the n=1 mode of the string's oscillation, which can be attributed to the self-field and is largely suppressed when the self-field is removed. We also demonstrate that this mode is predominantly sourced by variations along the direction parallel to the string, which is missing in the unconnected segment model, used by arXiv:2512.13653 to claim the effectiveness of J_s in suppressing the self-field's contribution to the spectrum.
ER -