# A Review of Axion Lasing in Astrophysics

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## Abstract

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## 1. Introduction

## 2. Axion Masers

#### 2.1. Maser Luminosity

#### 2.2. Parametric Resonance

## 3. Lasing Axions as Particles

#### 3.1. Spontaneous Emission

#### 3.2. Stimulated Emission Rate Equations

#### 3.3. A Simple Axion Cluster Model

#### 3.4. Parameters and Conditions

#### 3.5. Discussion

#### 3.6. Application—Superradiant Clouds

#### 3.7. Non-Spherical Cluster and Static Spacetime Modification

## 4. Comments

## Author Contributions

## Funding

## Data Availability Statement

## Conflicts of Interest

## Abbreviations

KSVZ | Kim, Shifman, Vainshtein, Zakharov |

DFSZ | Dine, Fischler, Srednicki, Zhitnitsky |

BH | black hole |

BLASTs | black hole lasers powered by axion superradiant instabilities |

pBHs | primordial black holes |

FRB | fast radio burst |

IGRB | isotropic gamma-ray background |

## References

- Peccei, R.D.; Quinn, H.R. CP Conservation in the Presence of Instantons. Phys. Rev. Lett.
**1977**, 38, 1440–1443. [Google Scholar] [CrossRef] - Weinberg, S. A New Light Boson? Phys. Rev. Lett.
**1978**, 40, 223–226. [Google Scholar] [CrossRef] - Barshay, S.; Faissner, H.; Rodenberg, R.; De Witt, H. Coherent Conversion of Very Light Pseudoscalar Bosons. Phys. Rev. Lett.
**1981**, 46, 1361–1364. [Google Scholar] [CrossRef] - Barroso, A.; Mukhopadhyay, N.C. Axions: To be or not to be? Phys. Lett. B
**1981**, 106, 91–94. [Google Scholar] [CrossRef] - Kim, J.E. Weak Interaction Singlet and Strong CP Invariance. Phys. Rev. Lett.
**1979**, 43, 103. [Google Scholar] [CrossRef] - Shifman, M.A.; Vainshtein, A.I.; Zakharov, V.I. Can Confinement Ensure Natural CP Invariance of Strong Interactions? Nucl. Phys. B
**1980**, 166, 493–506. [Google Scholar] [CrossRef] - Dine, M.; Fischler, W.; Srednicki, M. A Simple Solution to the Strong CP Problem with a Harmless Axion. Phys. Lett. B
**1981**, 104, 199–202. [Google Scholar] [CrossRef] - Zhitnitsky, A.R. On Possible Suppression of the Axion Hadron Interactions. Sov. J. Nucl. Phys.
**1980**, 31, 260. (In Russian) [Google Scholar] - di Cortona, G.G.; Hardy, E.; Vega, J.P.; Villadoro, G. The QCD axion, precisely. JHEP
**2016**, 2016, 34. [Google Scholar] [CrossRef] - Cheng, S.L.; Geng, C.Q.; Ni, W.T. Axion—Photon couplings in invisible axion models. Phys. Rev. D
**1995**, 52, 3132–3135. [Google Scholar] [CrossRef] - Sikivie, P. Experimental Tests of the Invisible Axion. Phys. Rev. Lett.
**1983**, 51, 1415–1417, Erratum in Phys. Rev. Lett.**1984**, 52, 695. [Google Scholar] [CrossRef] - Kim, J.E. Light Pseudoscalars, Particle Physics and Cosmology. Phys. Rept.
**1987**, 150, 1–177. [Google Scholar] [CrossRef] - Raffelt, G.G. Astrophysical methods to constrain axions and other novel particle phenomena. Phys. Rept.
**1990**, 198, 1–113. [Google Scholar] [CrossRef] - Marsh, D.J.E. Axion Cosmology. Phys. Rept.
**2016**, 643, 1–79. [Google Scholar] [CrossRef] - Braaten, E.; Zhang, H. Colloquium: The physics of axion stars. Rev. Mod. Phys.
**2019**, 91, 041002. [Google Scholar] [CrossRef] - Sikivie, P. Invisible Axion Search Methods. Rev. Mod. Phys.
**2021**, 93, 015004. [Google Scholar] [CrossRef] - Kolb, E.W.; Tkachev, I.I. Axion miniclusters and Bose stars. Phys. Rev. Lett.
**1993**, 71, 3051–3054. [Google Scholar] [CrossRef] [PubMed] - Kolb, E.W.; Tkachev, I.I. Nonlinear axion dynamics and formation of cosmological pseudosolitons. Phys. Rev. D
**1994**, 49, 5040–5051. [Google Scholar] [CrossRef] - Braaten, E.; Mohapatra, A.; Zhang, H. Dense Axion Stars. Phys. Rev. Lett.
**2016**, 117, 121801. [Google Scholar] [CrossRef] - Tkachev, I.I. Coherent scalar field oscillations forming compact astrophysical objects. Sov. Astron. Lett.
**1986**, 12, 305–308. [Google Scholar] - Kephart, T.W.; Weiler, T.J. Luminous axion clusters. Phys. Rev. Lett.
**1987**, 58, 171. [Google Scholar] [CrossRef] [PubMed] - Rosa, J.G.; Kephart, T.W. Stimulated Axion Decay in Superradiant Clouds around Primordial Black Holes. Phys. Rev. Lett.
**2018**, 120, 231102. [Google Scholar] [CrossRef] - Kibble, T.W.B. Topology of Cosmic Domains and Strings. J. Phys. A
**1976**, 9, 1387–1398. [Google Scholar] [CrossRef] - Tkachev, I.I. An Axionic Laser in the Center of a Galaxy? Phys. Lett. B
**1987**, 191, 41–45. [Google Scholar] [CrossRef] - Sato, H. Cosmic Strings and Rotation Velocity of Spiral Galaxies. Mod. Phys. Lett. A
**1986**, 1, 9. [Google Scholar] [CrossRef] - Silk, J.; Vilenkin, A. Cosmic Strings and Galaxy Formation. Phys. Rev. Lett.
**1984**, 53, 1700–1703. [Google Scholar] [CrossRef] - Braaten, E.; Mohapatra, A.; Zhang, H. Emission of Photons and Relativistic Axions from Axion Stars. Phys. Rev. D
**2017**, 96, 031901. [Google Scholar] [CrossRef] - Tkachev, I.I. Fast Radio Bursts and Axion Miniclusters. JETP Lett.
**2015**, 101, 1–6. [Google Scholar] [CrossRef] - Guendelman, E.I. Localized Axion Photon States in a Strong Magnetic Field. Phys. Lett. B
**2008**, 662, 227–230. [Google Scholar] [CrossRef] - Levkov, D.G.; Panin, A.G.; Tkachev, I.I. Radio-emission of axion stars. Phys. Rev. D
**2020**, 102, 023501. [Google Scholar] [CrossRef] - Sikivie, P.; Yang, Q. Bose-Einstein Condensation of Dark Matter Axions. Phys. Rev. Lett.
**2009**, 103, 111301. [Google Scholar] [CrossRef] [PubMed] - Erken, O.; Sikivie, P.; Tam, H.; Yang, Q. Cosmic axion thermalization. Phys. Rev. D
**2012**, 85, 063520. [Google Scholar] [CrossRef] - Hertzberg, M.P.; Schiappacasse, E.D. Dark Matter Axion Clump Resonance of Photons. JCAP
**2018**, 11, 004. [Google Scholar] [CrossRef] - Schiappacasse, E.D.; Hertzberg, M.P. Analysis of Dark Matter Axion Clumps with Spherical Symmetry. JCAP
**2018**, 01, 037, Erratum in JCAP**2018**, 03, E01. [Google Scholar] [CrossRef] - Hertzberg, M.P.; Schiappacasse, E.D. Scalar dark matter clumps with angular momentum. JCAP
**2018**, 08, 028. [Google Scholar] [CrossRef] - Kephart, T.W.; Weiler, T.J. Stimulated radiation from axion cluster evolution. Phys. Rev. D
**1995**, 52, 3226–3238. [Google Scholar] [CrossRef] - Kephart, T.W.; Weiler, T.J. A model of lasing axion clusters. Nucl. Phys. B Proc. Suppl.
**1999**, 72, 54–57. [Google Scholar] [CrossRef] - Fridman, A.M.; Polyachenko, V.L. Physics of Gravitating Systems; Springer Science+Business Media: New York, NY, USA, 1984. [Google Scholar] [CrossRef]
- Kaplan, D.B. Opening the Axion Window. Nucl. Phys. B
**1985**, 260, 215–226. [Google Scholar] [CrossRef] - Brito, R.; Cardoso, V.; Pani, P. Superradiance: New Frontiers in Black Hole Physics; Lecture Notes in Physics; Springer Nature: Cham, Switzerland, 2020; Volume 906, pp. 1–237. ISBN 978-3-319-18999-4/978-3-319-19000-6/978-3-030-46621-3/978-3-030-46622-0. [Google Scholar] [CrossRef]
- Rosa, J.G. Testing black hole superradiance with pulsar companions. Phys. Lett. B
**2015**, 749, 226–230. [Google Scholar] [CrossRef] - Rosa, J.G. Superradiance in the sky. Phys. Rev. D
**2017**, 95, 064017. [Google Scholar] [CrossRef] - Leite, L.C.S.; Dolan, S.R.; Crispino, L.C.B. Absorption of electromagnetic and gravitational waves by Kerr black holes. Phys. Lett. B
**2017**, 774, 130–134. [Google Scholar] [CrossRef] - Carr, B.J.; Hawking, S.W. Black holes in the early Universe. Mon. Not. Roy. Astron. Soc.
**1974**, 168, 399–415. [Google Scholar] [CrossRef] - Lorimer, D.R.; Bailes, M.; McLaughlin, M.A.; Narkevic, D.J.; Crawford, F. A bright millisecond radio burst of extragalactic origin. Science
**2007**, 318, 777. [Google Scholar] [CrossRef] [PubMed] - Thornton, D.; Stappers, B.; Bailes, M.; Barsdell, B.R.; Bates, S.D.; Bhat, N.D.R.; Burgay, M.; Burke-Spolaor, S.; Champion, D.J.; Coster, P.; et al. A Population of Fast Radio Bursts at Cosmological Distances. Science
**2013**, 341, 53–56. [Google Scholar] [CrossRef] [PubMed] - Petroff, E.; Barr, E.D.; Jameson, A.; Keane, E.F.; Bailes, M.; Kramer, M.; Morello, V.; Tabbara, D.; van Straten, W. FRBCAT: The Fast Radio Burst Catalogue. Publ. Astron. Soc. Austral.
**2016**, 33, e045. [Google Scholar] [CrossRef] - Spitler, L.G.; Scholz, P.; Hessels, J.W.T.; Bogdanov, S.; Brazier, A.; Camilo, F.; Chatterjee, S.; Cordes, J.M.; Crawford, F.; Deneva, J.; et al. A Repeating Fast Radio Burst. Nature
**2016**, 531, 202. [Google Scholar] [CrossRef] - Chatterjee, S.; Law, C.J.; Wharton, R.S.; Burke-Spolaor, S.; Hessels, J.W.T.; Bower, G.C.; Cordes, J.M.; Tendulkar, S.P.; Bassa, C.G.; Demorest, P.; et al. The direct localization of a fast radio burst and its host. Nature
**2017**, 541, 58. [Google Scholar] [CrossRef] [PubMed] - Marcote, B.; Paragi, Z.; Hessels, J.W.T.; Keimpema, A.; van Langevelde, H.J.; Huang, Y.; Bassa, C.G.; Bogdanov, S.; Bower, G.C.; Burke-Spolaor, S.; et al. The Repeating Fast Radio Burst FRB 121102 as Seen on Milliarcsecond Angular Scales. Astrophys. J. Lett.
**2017**, 834, L8. [Google Scholar] [CrossRef] - Tendulkar, S.P.; Bassa, C.; Cordes, J.M.; Bower, G.C.; Law, C.J.; Chatterjee, S.; Adams, E.A.K.; Bogdanov, S.; Burke-Spolaor, S.; Butler, B.J.; et al. The Host Galaxy and Redshift of the Repeating Fast Radio Burst FRB 121102. Astrophys. J. Lett.
**2017**, 834, L7. [Google Scholar] [CrossRef] - Ferraz, P.B.; Kephart, T.W.; Rosa, J.G. Superradiant pion clouds around primordial black holes. JCAP
**2022**, 07, 026. [Google Scholar] [CrossRef] - Spieksma, T.F.M.; Cannizzaro, E.; Ikeda, T.; Cardoso, V.; Chen, Y. Superradiance: Axionic couplings and plasma effects. Phys. Rev. D
**2023**, 108, 063013. [Google Scholar] [CrossRef] - Chen, L.; Kephart, T.W. Photon directional profile from stimulated decay of axion clouds with arbitrary momentum distributions. Phys. Rev. D
**2020**, 101, 103033. [Google Scholar] [CrossRef] - Chen, L.; Kephart, T.W. Photon directional profile from stimulated decay of axion clouds with nonspherical axion spatial distributions. Phys. Rev. D
**2020**, 102, 096010. [Google Scholar] [CrossRef] - Chen, L.; Huang, D.; Geng, C.Q. Effects of stimulated emission and superradiant growth of non-spherical axion cluster. arXiv
**2023**, arXiv:2311.01819. [Google Scholar] - Chen, L.; Kephart, T.W. Stimulated radiation from axion cluster evolution in static spacetimes. JCAP
**2021**, 09, 034. [Google Scholar] [CrossRef]

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**MDPI and ACS Style**

Chen, L.; Kephart, T.W.
A Review of Axion Lasing in Astrophysics. *Universe* **2024**, *10*, 24.
https://doi.org/10.3390/universe10010024

**AMA Style**

Chen L, Kephart TW.
A Review of Axion Lasing in Astrophysics. *Universe*. 2024; 10(1):24.
https://doi.org/10.3390/universe10010024

**Chicago/Turabian Style**

Chen, Liang, and Thomas W. Kephart.
2024. "A Review of Axion Lasing in Astrophysics" *Universe* 10, no. 1: 24.
https://doi.org/10.3390/universe10010024