The Gravitational Spectral Radio Forest: A Signature of Primordial Black Holes
P. George Christopher, K. Hari, S. Shankaranarayanan
TLDR
This paper proposes using interstellar hydrogen as a quantum sensor to detect asteroid-mass Primordial Black Holes via a novel gravitational spectral radio forest.
Key contributions
- Interstellar hydrogen acts as a quantum sensor for spacetime curvature.
- Asteroid-mass PBHs induce symmetric splitting of hydrogen's 2P3/2 state.
- This creates a "gravitational spectral radio forest" from a 9.9 GHz absorption line.
- Enhanced absorption spectrum due to hydrogen accretion makes it a high-contrast target.
Why it matters
This work introduces a novel, high-contrast method to detect asteroid-mass Primordial Black Holes, which are candidates for dark matter. It offers a concrete target for upcoming radio surveys, potentially advancing our understanding of the universe's dark matter composition.
Original Abstract
We propose a novel gravitational signature to detect Primordial Black Hole (PBH) dark matter by treating interstellar hydrogen as a quantum sensor for spacetime curvature. Focusing on H II regions, we demonstrate that the Riemann tidal tensor of an \emph{asteroid-mass} PBH induces a symmetric splitting of the $2P_{3/2}$ state in bound hydrogen atoms. This relativistic effect redistributes $9.9\,\mathrm{GHz}$ absorption line into a gravitational spectral radio forest with a bandwidth $\sim 2\,\mathrm{GHz}$. By accounting for active accretion of Hydrogen atoms and the resulting density-squared emission measure within the Bondi radius, we find a relatively enhanced absorption spectrum. This feature presents a concrete, high-contrast target for upcoming radio-surveys to constrain PBH populations in the dark matter sector.
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