Pseudo-Nambu-Goldstone Boson Motion from Thermal Thresholds
Abstract
Coherent motion of light scalar fields in the early Universe is typically attributed to an initial displacement, a primordial velocity, or a prescribed temperature-dependent potential. We identify a distinct microscopic mechanism in which differential thermal evolution of multiple non-aligned symmetry-breaking sources rotates the effective vacuum direction of a pseudo-Nambu--Goldstone boson (pNGB), driving motion from an initially stationary minimum. The mechanism is realized in the Majoron sector of a Type-I seesaw mechanism, where heavy neutrinos with separated thermal thresholds supply the required differential thermal evolution. For a representative benchmark, the thermal source direction rotates by |ΔθT|≃0.76~rad and drives the Majoron to a peak velocity |θ̇|/H≃0.62, while the field tracks the moving minimum to sub-milliradian accuracy. This establishes a microscopic finite-temperature origin for pNGB motion, with implications for spontaneous leptogenesis and, more generally, for any system with multiple non-aligned symmetry-breaking sources that evolve differently with temperature.
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BibTeX
@misc{khan2026pseudonambugoldstone,
title = {{Pseudo-Nambu-Goldstone Boson Motion from Thermal Thresholds}},
author = {Mussawir Khan and Ali Muhammad and Tianjun Li},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.04265},
eprint = {2610.04265},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.04265},
}
RIS
TY - UNPB
TI - Pseudo-Nambu-Goldstone Boson Motion from Thermal Thresholds
AU - Mussawir Khan
AU - Ali Muhammad
AU - Tianjun Li
PY - 2026
DA - 2026/10/03
PB - arXiv
DO - 10.48550/arxiv.2610.04265
UR - https://arxiv.org/abs/2610.04265
AB - Coherent motion of light scalar fields in the early Universe is typically attributed to an initial displacement, a primordial velocity, or a prescribed temperature-dependent potential. We identify a distinct microscopic mechanism in which differential thermal evolution of multiple non-aligned symmetry-breaking sources rotates the effective vacuum direction of a pseudo-Nambu--Goldstone boson (pNGB), driving motion from an initially stationary minimum. The mechanism is realized in the Majoron sector of a Type-I seesaw mechanism, where heavy neutrinos with separated thermal thresholds supply the required differential thermal evolution. For a representative benchmark, the thermal source direction rotates by |Δθ_T|≃0.76~rad and drives the Majoron to a peak velocity |θ̇|/H≃0.62, while the field tracks the moving minimum to sub-milliradian accuracy. This establishes a microscopic finite-temperature origin for pNGB motion, with implications for spontaneous leptogenesis and, more generally, for any system with multiple non-aligned symmetry-breaking sources that evolve differently with temperature.
ER -