### Abstract

We consider a superradiance effect around rotating dilatonic black holes. We analyze two cases: one is an exact solution with the coupling constant α = 3, which effective action is reduced from the 5-dimensional Kaluza-Klein theory, and the other is a slowly rotating dilatonic black holes with arbitrary coupling constant. We find that there exists a critical value (α ∼ 1), which is predicted from a superstring model, and the superradiant emission rate with coupling larger than the critical value becomes much higher than the Kerr-Newman case (α = 0) in the maximally charged limit. Consequently, 4-dimensional primordial black holes in higher dimensional unified theories are either rotating but almost neutral or charged but effectively non-rotating.

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

Pages (from-to) | 29-34 |

Number of pages | 6 |

Journal | Physics Letters B |

Volume | 340 |

Issue number | 1-2 |

DOIs | |

Publication status | Published - 1994 Dec 1 |

### ASJC Scopus subject areas

- Nuclear and High Energy Physics

### Cite this

*Physics Letters B*,

*340*(1-2), 29-34. https://doi.org/10.1016/0370-2693(94)91293-9

**Superradiance around rotating dilatonic black holes.** / Koga, Jun ichirou; Maeda, Keiichi.

Research output: Contribution to journal › Article

*Physics Letters B*, vol. 340, no. 1-2, pp. 29-34. https://doi.org/10.1016/0370-2693(94)91293-9

}

TY - JOUR

T1 - Superradiance around rotating dilatonic black holes

AU - Koga, Jun ichirou

AU - Maeda, Keiichi

PY - 1994/12/1

Y1 - 1994/12/1

N2 - We consider a superradiance effect around rotating dilatonic black holes. We analyze two cases: one is an exact solution with the coupling constant α = 3, which effective action is reduced from the 5-dimensional Kaluza-Klein theory, and the other is a slowly rotating dilatonic black holes with arbitrary coupling constant. We find that there exists a critical value (α ∼ 1), which is predicted from a superstring model, and the superradiant emission rate with coupling larger than the critical value becomes much higher than the Kerr-Newman case (α = 0) in the maximally charged limit. Consequently, 4-dimensional primordial black holes in higher dimensional unified theories are either rotating but almost neutral or charged but effectively non-rotating.

AB - We consider a superradiance effect around rotating dilatonic black holes. We analyze two cases: one is an exact solution with the coupling constant α = 3, which effective action is reduced from the 5-dimensional Kaluza-Klein theory, and the other is a slowly rotating dilatonic black holes with arbitrary coupling constant. We find that there exists a critical value (α ∼ 1), which is predicted from a superstring model, and the superradiant emission rate with coupling larger than the critical value becomes much higher than the Kerr-Newman case (α = 0) in the maximally charged limit. Consequently, 4-dimensional primordial black holes in higher dimensional unified theories are either rotating but almost neutral or charged but effectively non-rotating.

UR - http://www.scopus.com/inward/record.url?scp=0040331316&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0040331316&partnerID=8YFLogxK

U2 - 10.1016/0370-2693(94)91293-9

DO - 10.1016/0370-2693(94)91293-9

M3 - Article

AN - SCOPUS:0040331316

VL - 340

SP - 29

EP - 34

JO - Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics

JF - Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics

SN - 0370-2693

IS - 1-2

ER -