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Dyonic Kerr-Sen Black Hole's Resonant Scattering: Absorption and Superradiance

S. Katewongveerachart, D. Senjaya

Abstract

We analytically investigate scalar superradiant scattering in the rotating dyonic Kerr-Sen black hole of Einstein-Maxwell-Dilaton-Axion theory. Starting from the separable Klein-Gordon equation for a massive neutral scalar field, we work in the low-frequency and slow-rotation regime and employ the analytical asymptotic matching (AAM) method to compute the reflection coefficient and the associated superradiant amplification factor. Since an exact global scattering solution is not available in this four-charge geometry, the AAM framework enables a controlled analytic treatment of the near-and far-region dynamics. We provide detailed and systematic derivations of the matching procedure leading to the closed-form amplification formula. The superradiant condition is obtained explicitly and we demonstrate that energy extraction occurs exclusively for co-rotating modes satisfying $Ω< m Ω_H$. We show that the presence of electric and magnetic charges suppresses the amplification relative to the Kerr limit, whereas lighter co-rotating scalar fields broaden the superradiant window and enhance the efficiency of rotational energy extraction.

Dyonic Kerr-Sen Black Hole's Resonant Scattering: Absorption and Superradiance

Abstract

We analytically investigate scalar superradiant scattering in the rotating dyonic Kerr-Sen black hole of Einstein-Maxwell-Dilaton-Axion theory. Starting from the separable Klein-Gordon equation for a massive neutral scalar field, we work in the low-frequency and slow-rotation regime and employ the analytical asymptotic matching (AAM) method to compute the reflection coefficient and the associated superradiant amplification factor. Since an exact global scattering solution is not available in this four-charge geometry, the AAM framework enables a controlled analytic treatment of the near-and far-region dynamics. We provide detailed and systematic derivations of the matching procedure leading to the closed-form amplification formula. The superradiant condition is obtained explicitly and we demonstrate that energy extraction occurs exclusively for co-rotating modes satisfying . We show that the presence of electric and magnetic charges suppresses the amplification relative to the Kerr limit, whereas lighter co-rotating scalar fields broaden the superradiant window and enhance the efficiency of rotational energy extraction.
Paper Structure (19 sections, 149 equations, 6 figures)

This paper contains 19 sections, 149 equations, 6 figures.

Table of Contents

  1. Introduction
  2. The Dyonic Kerr–Sen Black Hole
  3. The Boson Dynamics
  4. The Polar Equation
  5. The Radial Equation
  6. Resonant Boson Scattering
  7. Analytical Asymptotic Matching
  8. Far Field Limit
  9. Near Horizon Solution
  10. Matching The Solutions
  11. Superradiance Amplification
  12. Greybody Factor
  13. Superradiance Energy Extraction
  14. Conclusions
  15. Normal Form
  16. ...and 4 more sections

Figures (6)

  • Figure 1: Amplification factor $Z_{l,m_l,a,P,Q}$ versus frequency $\Omega$ for several values of $l, m_l$ and $a$, with fixed $\Omega_0=0.1$ and $r_s=1$.
  • Figure 2: Amplification factor $Z_{l,m_l,a,P,Q}$ versus frequency $\Omega$ for several values of $P, Q$ with fixed $\Omega_0=0.1$ and $r_s=1, a=0.15, l=m_l=3$.
  • Figure 3: Amplification factor $Z_{l,m_l,a,P,Q}$ versus frequency $\Omega$ for several values of $\Omega_0$ with fixed $r_s=1, a=0.2, P=0.1, Q=0,2, l=m_l=3$.
  • Figure 4: Greybody factor profile of the $l=3, m_l=1$ mode for various values of the rotation parameter $a$, with $\Omega_0=0.05, r_s=1, P=0.1$ and $Q=0.2$ fixed.
  • Figure 5: Greybody factor profile of the $l=3, m_l=1$ mode for various values of the dyonic charge $P$, with $\Omega_0=0.05, r_s=1, Q=0.2$ and $a=0.3$ fixed.
  • ...and 1 more figures