CMB Injection Bounds on Moduli Fields
Abstract
Light scalar fields with gravitational strength interactions (moduli) are ubiquitous in string, supergravity, and extra-dimensional models. If produced in the early universe with lifetimes exceeding the epoch of recombination, slowly decaying moduli inject energetic particles into the Standard Model plasma, leaving distinct imprints on the cosmic microwave background (CMB). In this paper we systematically derive CMB injection bounds on light moduli (103 eV≤ mmod≤ 108 eV) across the primary cosmological production channels: vacuum misalignment, heavy scalar/inflaton decay, thermal emission from the primordial plasma including production from a Hagedorn phase of hot strings. We show that these injection bounds impose stringent constraints that are complementary to both the standard cosmological moduli problem and fifth force bounds.
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BibTeX
@misc{agarwal2026injection,
title = {{CMB Injection Bounds on Moduli Fields}},
author = {Naman Agarwal and Andrew R. Frey and Ratul Mahanta and Anshuman Maharana and Fernando Quevedo and Gonzalo Villa},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.38151},
eprint = {2609.38151},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.38151},
}
RIS
TY - UNPB
TI - CMB Injection Bounds on Moduli Fields
AU - Naman Agarwal
AU - Andrew R. Frey
AU - Ratul Mahanta
AU - Anshuman Maharana
AU - Fernando Quevedo
AU - Gonzalo Villa
PY - 2026
DA - 2026/09/29
PB - arXiv
DO - 10.48550/arxiv.2609.38151
UR - https://arxiv.org/abs/2609.38151
AB - Light scalar fields with gravitational strength interactions (moduli) are ubiquitous in string, supergravity, and extra-dimensional models. If produced in the early universe with lifetimes exceeding the epoch of recombination, slowly decaying moduli inject energetic particles into the Standard Model plasma, leaving distinct imprints on the cosmic microwave background (CMB). In this paper we systematically derive CMB injection bounds on light moduli (10^3 eV≤ m_mod≤ 10^8 eV) across the primary cosmological production channels: vacuum misalignment, heavy scalar/inflaton decay, thermal emission from the primordial plasma including production from a Hagedorn phase of hot strings. We show that these injection bounds impose stringent constraints that are complementary to both the standard cosmological moduli problem and fifth force bounds.
ER -