[论文解读] Quasinormal Modes, Grebody Factors, and Hawking Radiation Sparsity of Black Holes Influenced by a Global Monopole Charge in Kalb-Ramond Gravity

Anshuman Baruah, Yassine Sekhmani+3 more|ArXiv.org|Feb 19, 2025

Black Holes and Theoretical Physics被引用 3

一句话总结

该论文利用高精度的 Padé-averaged WKB 与时域方法，分析带全球单极子电荷的 Kalb-Ramond 黑洞的准规范模、灰体因子界限和霍金辐射稀疏性，探讨参数效应。

ABSTRACT

Kalb-Ramond (KR) gravity is an intriguing model incorporating local Lorentz violation, and black hole (BH) solutions are known to exist. In this study, we investigate some crucial aspects of BHs endowed with a global monopole charge in the self-interacting KR field. Specifically, we study the quasinormal modes (QNMs) corresponding to scalar, electromagnetic, and gravitational perturbations; derive rigorous bounds for the greybody factors (GBFs); and examine the sparsity of Hawking radiation. The effects of the model parameters $\ell$ (Lorentz-violating parameter in KR gravity) and $η$ (monopole charge) on these phenomena are elaborated. First, QNMs are evaluated with high precision using the 13 extsuperscript{th}-order Padé-averaged WKB method and cross-examined via time-domain analyses within an acceptable parameter space. The results show that the estimated QNMs are more sensitive to $\ell$; however, both model parameters influence the frequency spectra. The derived bounds on the GBFs aid in further constraining the parameter space. It is shown that $\ell$ and $η$ have a similar effect on the greybody bounds. Furthermore, positive and negative values of $\ell$ have opposing effects in that the bounds are reversed for the two cases. The analyses of the Hawking radiation sparsity highlight the effect of $\ell$, and two scenarios are noted: either the radiation emitted is less sparse than Hawking radiation, or it is more sparse during the evaporation phase. Thus, this work presents a comprehensive account of BHs in KR gravity with a global monopole charge.

研究动机与目标

• Investigate black hole perturbations in Kalb-Ramond gravity with a global monopole charge.
• Quantify how the Lorentz-violating parameter ell and monopole charge eta affect QNMs, GBFs, and Hawking radiation.
• derive rigorous bounds on greybody factors to constrain parameter space.
• examine the sparsity of Hawking radiation during evaporation under KR gravity.
• compare scalar, electromagnetic, and gravitational perturbations to assess universal and mode-specific effects.

提出的方法

• Compute quasinormal modes in scalar, electromagnetic, and gravitational sectors using the 13th-order Pade9-averaged WKB method.
• Cross-check QNM frequencies with time-domain analyses within an admissible parameter space.
• derive rigorous bounds for greybody factors from the perturbation potentials and model parameters, and compare their dependence on ell and eta.
• analyze Hawking radiation sparsity and discuss scenarios where radiation is more or less sparse compared to Hawking expectations.
• treat perturbations in a tetrad formalism and recast into Schrd6dinger-like wave equations with effective potentials.

实验结果

研究问题

• RQ1 How do the KR gravity parameters ell and eta influence scalar, electromagnetic, and gravitational QNMs of a KR black hole with a global monopole charge?
• RQ2 What bounds can be established for greybody factors in this setup, and how do they constrain the parameter space?
• RQ3 How is Hawking radiation sparsity affected by ell and eta during black hole evaporation?
• RQ4 Do scalar, EM, and gravitational perturbations exhibit consistent or distinct responses to the KR monopole background?

主要发现

• QNMs are more sensitive to the Lorentz-violating parameter ell, with real parts increasing and imaginary parts indicating stronger damping as ell grows.
• Both ell and monopole charge eta similarly influence greybody factor bounds, with sign of ell producing reversed bounds for positive vs negative values.
• For scalar perturbations, increasing eta weakens damping (|omega_im| decreases), while real parts show a subtle monotonic rise across overtones.
• Electromagnetic QNMs show weak ell sensitivity in real parts but a slight increase in damping with ell, and damping decreases modestly with larger eta.
• Gravitational QNMs exhibit an increasing trend in the real part of frequencies with ell across overtones, and damping behavior follows a similar pattern to scalar perturbations.
• Hawking radiation sparsity can be either more or less sparse than Hawking radiation depending on ell, indicating two notable evaporation scenarios.