Exploring Cosmic Rays from Gravity-Limited Acceleration at Supermassive Black Holes
Abstract
We show that horizon-scale magnetic fields around supermassive black holes (SMBHs), only limited by gravity, yield a universal, model-independent ceiling on electromagnetic energy density. For rotating SMBHs, this field enables particle acceleration up to ∼ 1027\,eV set solely by fundamental constants. We identify a parameter space in accretion rate and magnetic field strength in which quiescent nuclei simultaneously satisfy the transparency conditions for Ultra-High-Energy Cosmic Rays (UHECR) escape and the field requirements for reaching Ultra-High Energies (UHE), naturally complementing photon-rich Active Galactic Nuclei (AGN), which favor neutrino production but suppress UHECR escape. We observe that, when including curvature energy losses, the energy of the primaries scales weakly as Ecurv ∝ M1/4 and allows to achieve UHE across different compositions and SMBHs masses (106--1010 M⊙), without requiring extreme spins or super-Eddington accretion. A cross-correlation of the Pierre Auger Observatory (PAO) public data with galaxies hosting reliably measured SMBH masses, separating AGN from quiescent hosts, reveals marginal local excesses (≲ 2.8σ) consistent with isotropy after correcting for the look-elsewhere effect. The framework provides a direct link between black-hole physics and the maximum energies of cosmic particles, and defines concrete observational tests for next-generation UHECR datasets.
Versions
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BibTeX
@misc{manao2026exploring,
title = {{Exploring Cosmic Rays from Gravity-Limited Acceleration at Supermassive Black Holes}},
author = {Elena Manao and Elisa Resconi and Frank M. Rieger and Paolo Padovani and Gia Dvali},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.23393},
eprint = {2610.23393},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.23393},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Exploring Cosmic Rays from Gravity-Limited Acceleration at Supermassive Black Holes
AU - Elena Manao
AU - Elisa Resconi
AU - Frank M. Rieger
AU - Paolo Padovani
AU - Gia Dvali
PY - 2026
DA - 2026/10/16
PB - arXiv
DO - 10.48550/arxiv.2610.23393
UR - https://arxiv.org/abs/2610.23393
AB - We show that horizon-scale magnetic fields around supermassive black holes (SMBHs), only limited by gravity, yield a universal, model-independent ceiling on electromagnetic energy density. For rotating SMBHs, this field enables particle acceleration up to ∼ 10^27\,eV set solely by fundamental constants. We identify a parameter space in accretion rate and magnetic field strength in which quiescent nuclei simultaneously satisfy the transparency conditions for Ultra-High-Energy Cosmic Rays (UHECR) escape and the field requirements for reaching Ultra-High Energies (UHE), naturally complementing photon-rich Active Galactic Nuclei (AGN), which favor neutrino production but suppress UHECR escape. We observe that, when including curvature energy losses, the energy of the primaries scales weakly as E_curv ∝ M^1/4 and allows to achieve UHE across different compositions and SMBHs masses (10^6--10^10 M_⊙), without requiring extreme spins or super-Eddington accretion. A cross-correlation of the Pierre Auger Observatory (PAO) public data with galaxies hosting reliably measured SMBH masses, separating AGN from quiescent hosts, reveals marginal local excesses (≲ 2.8σ) consistent with isotropy after correcting for the look-elsewhere effect. The framework provides a direct link between black-hole physics and the maximum energies of cosmic particles, and defines concrete observational tests for next-generation UHECR datasets.
ER -