Quantum Field Theory Of Cosmological Perturbations Induced By Ultralight Dark Matter
Abstract
The growth of primordial perturbations during the matter-dominated era is primarily driven by dark matter. Ultralight scalar fields (ULDM) are a promising candidate for this role, conventionally modeled as operating in a classical, high-occupation regime. In this work, we develop a first-principles field-theoretic framework to investigate the impact of ULDM on linear cosmological perturbations during matter domination, explicitly retaining its quantum nature. Deriving a closed equation for the graviton field dynamics, we compute and regularize its source terms for a generic Gaussian initial state of the ULDM field within the adiabatic (WKB) approximation, employing the middle-point working assumption for non-local terms. After gauge-fixing we find that, contrary to previous claims, the classical condensate of ULDM has no influence on gravitational wave propagation. However, the time-dependent graviton effective mass induced by quantum pressure of the squeezed state can drive parametric resonance in specific primordial gravitational wave modes. We demonstrate this growth is negligible for non-relativistic ULDM at matter-radiation equality under the assumption of a power-law squeezing spectrum for masses in the range m ∼ 10−21−10−24 eV.
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BibTeX
@misc{prokopec2026quantum,
title = {{Quantum Field Theory Of Cosmological Perturbations Induced By Ultralight Dark Matter}},
author = {Tomislav Prokopec and Marco Vecchioni},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2607.27133},
eprint = {2607.27133},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2607.27133},
}
RIS
TY - UNPB
TI - Quantum Field Theory Of Cosmological Perturbations Induced By Ultralight Dark Matter
AU - Tomislav Prokopec
AU - Marco Vecchioni
PY - 2026
DA - 2026/10/14
PB - arXiv
DO - 10.48550/arxiv.2607.27133
UR - https://arxiv.org/abs/2607.27133
AB - The growth of primordial perturbations during the matter-dominated era is primarily driven by dark matter. Ultralight scalar fields (ULDM) are a promising candidate for this role, conventionally modeled as operating in a classical, high-occupation regime. In this work, we develop a first-principles field-theoretic framework to investigate the impact of ULDM on linear cosmological perturbations during matter domination, explicitly retaining its quantum nature. Deriving a closed equation for the graviton field dynamics, we compute and regularize its source terms for a generic Gaussian initial state of the ULDM field within the adiabatic (WKB) approximation, employing the middle-point working assumption for non-local terms. After gauge-fixing we find that, contrary to previous claims, the classical condensate of ULDM has no influence on gravitational wave propagation. However, the time-dependent graviton effective mass induced by quantum pressure of the squeezed state can drive parametric resonance in specific primordial gravitational wave modes. We demonstrate this growth is negligible for non-relativistic ULDM at matter-radiation equality under the assumption of a power-law squeezing spectrum for masses in the range m ∼ 10^−21−10^−24 eV.
ER -