### Abstract

Original language | English |
---|---|

Article number | 043504 |

Journal | Phys. Rev. D. |

Volume | 101 |

Number of pages | 33 |

ISSN | 2470-0010 |

DOIs | |

Publication status | Published - 4. Feb 2020 |

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### Cite this

*Phys. Rev. D.*,

*101*, [043504]. https://doi.org/10.1103/PhysRevD.101.043504

}

*Phys. Rev. D.*, vol. 101, 043504. https://doi.org/10.1103/PhysRevD.101.043504

**Gravitational Absorption Lines.** / Palessandro, Andrea; Sloth, Martin S.

Research output: Contribution to journal › Journal article › Research › peer-review

TY - JOUR

T1 - Gravitational Absorption Lines

AU - Palessandro, Andrea

AU - Sloth, Martin S.

PY - 2020/2/4

Y1 - 2020/2/4

N2 - We consider the gravitational analogue of Lyman-alpha absorption lines in astronomical spectroscopy. If Einstein gravity with minimally coupled matter is valid up to the Planck scale, quantum bound states absorb gravitons of a specific frequency with Planckian cross section, $\sigma_{\text{abs}} \approx l_p^2$. Consequently, one can show that gravitational absorption by bound states is inefficient in ordinary gravity. If observed, gravitational absorption lines would therefore constitute a powerful smoking gun of new exotic astrophysical bound states (near extremal bound states) or new gravitational physics, as well as give direct evidence of the quantized nature of the gravitational field. We provide, as an example of new gravitational physics near the Planck scale, a non-minimal coupling of the matter fields which breaks the equivalence principle on-shell. We lay out a model in which absorption lines in the primordial gravitational wave spectrum are produced as a consequence of this coupling.

AB - We consider the gravitational analogue of Lyman-alpha absorption lines in astronomical spectroscopy. If Einstein gravity with minimally coupled matter is valid up to the Planck scale, quantum bound states absorb gravitons of a specific frequency with Planckian cross section, $\sigma_{\text{abs}} \approx l_p^2$. Consequently, one can show that gravitational absorption by bound states is inefficient in ordinary gravity. If observed, gravitational absorption lines would therefore constitute a powerful smoking gun of new exotic astrophysical bound states (near extremal bound states) or new gravitational physics, as well as give direct evidence of the quantized nature of the gravitational field. We provide, as an example of new gravitational physics near the Planck scale, a non-minimal coupling of the matter fields which breaks the equivalence principle on-shell. We lay out a model in which absorption lines in the primordial gravitational wave spectrum are produced as a consequence of this coupling.

KW - hep-th

KW - astro-ph.CO

KW - gr-qc

U2 - 10.1103/PhysRevD.101.043504

DO - 10.1103/PhysRevD.101.043504

M3 - Journal article

VL - 101

JO - Physical Review D

JF - Physical Review D

SN - 2470-0010

M1 - 043504

ER -