Particle production from bubble collisions
Abstract
Collisions of ultra-relativistic bubbles during cosmological phase transitions can produce particles much heavier than the transition scale. Previous analyses modelled this process as the off-shell decay of the scalar background. We show that its results parametrically overestimate hard particle production and depend on the gauge choice and the coordinate choice in field space. We propose an alternative formalism, analogous to the partonic description of high-energy collisions. In the ultra-relativistic limit, the colliding bubbles undergo nearly free passage and hard production arises from on-shell scatterings among the quanta constituting the Lorentz-contracted walls. We apply this approach to heavy scalar, fermion, and vector particle production, and study the implications for dark matter, leptogenesis, graviton production and primordial gravitational waves.
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BibTeX
@misc{ghoshal2026particle,
title = {{Particle production from bubble collisions}},
author = {Anish Ghoshal and Pratyay Pal and Alessandro Strumia},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2607.15279},
eprint = {2607.15279},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2607.15279},
}
RIS
TY - UNPB
TI - Particle production from bubble collisions
AU - Anish Ghoshal
AU - Pratyay Pal
AU - Alessandro Strumia
PY - 2026
DA - 2026/10/09
PB - arXiv
DO - 10.48550/arxiv.2607.15279
UR - https://arxiv.org/abs/2607.15279
AB - Collisions of ultra-relativistic bubbles during cosmological phase transitions can produce particles much heavier than the transition scale. Previous analyses modelled this process as the off-shell decay of the scalar background. We show that its results parametrically overestimate hard particle production and depend on the gauge choice and the coordinate choice in field space. We propose an alternative formalism, analogous to the partonic description of high-energy collisions. In the ultra-relativistic limit, the colliding bubbles undergo nearly free passage and hard production arises from on-shell scatterings among the quanta constituting the Lorentz-contracted walls. We apply this approach to heavy scalar, fermion, and vector particle production, and study the implications for dark matter, leptogenesis, graviton production and primordial gravitational waves.
ER -