Spectral Fingerprints Beyond Degeneracies in Primordial Gravitational-Wave Sources
Abstract
Stochastic gravitational-wave backgrounds from different primordial mechanisms can exhibit identical peak frequencies and amplitudes, leaving their origin degenerate. We show that this degeneracy can be broken by the broadband spectral response of the gravitational-wave source. By comparing scalar-induced and gauge-field-induced gravitational waves with the same primordial spectral profile and cosmological evolution, we isolate the imprint of the tensor-source dynamics. Although both mechanisms exhibit the same infrared scaling, they develop distinct spectral shapes near the peak and different ultraviolet asymptotes. The local spectral index ngw and its running αgw further characterize this source-dependent evolution, providing a spectral fingerprint beyond the peak observables. These results show that broadband, multi-frequency observations can probe the production mechanism of a primordial gravitational-wave background even when its peak frequency and amplitude are degenerate.
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BibTeX
@misc{maiti2026spectral,
title = {{Spectral Fingerprints Beyond Degeneracies in Primordial Gravitational-Wave Sources}},
author = {Subhasis Maiti},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2608.17002},
eprint = {2608.17002},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2608.17002},
}
RIS
TY - UNPB
TI - Spectral Fingerprints Beyond Degeneracies in Primordial Gravitational-Wave Sources
AU - Subhasis Maiti
PY - 2026
DA - 2026/09/13
PB - arXiv
DO - 10.48550/arxiv.2608.17002
UR - https://arxiv.org/abs/2608.17002
AB - Stochastic gravitational-wave backgrounds from different primordial mechanisms can exhibit identical peak frequencies and amplitudes, leaving their origin degenerate. We show that this degeneracy can be broken by the broadband spectral response of the gravitational-wave source. By comparing scalar-induced and gauge-field-induced gravitational waves with the same primordial spectral profile and cosmological evolution, we isolate the imprint of the tensor-source dynamics. Although both mechanisms exhibit the same infrared scaling, they develop distinct spectral shapes near the peak and different ultraviolet asymptotes. The local spectral index n_gw and its running α_gw further characterize this source-dependent evolution, providing a spectral fingerprint beyond the peak observables. These results show that broadband, multi-frequency observations can probe the production mechanism of a primordial gravitational-wave background even when its peak frequency and amplitude are degenerate.
ER -