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arXiv 2004.01662gr-qcastro-ph.HEhep-th
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四维Einstein-Gauss-Bonnet黑洞周围的薄吸积盘

Thin Accretion Disk around a four-dimensional Einstein-Gauss-Bonnet Black Hole

Cheng Liu, Tao Zhu, Qiang Wu

备注：
7 pages, 5 figures; V2: references added and some typos are corrected; v3: 10 pages, 6 figures, version to appear in Chinese Physics C
发表信息：
Chinese Physics C Vol. 45, No. 1 (2021) 015105
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摘要：

最近Glavan和Lin提出了一个新的四维Einstein-Gauss-Bonnet（4 EGB）引力理论[D. Glavan和C. Lin，Phys. Rev. Lett. 124，081301（2020）]，其包括通过使用高斯-博内耦合常数$α\to α/(D-4)$在极限$D\to 4$中的重新缩放的正则化高斯-博内项。这个理论也被重新表述为一个特定的类Horndeski理论与一个额外的标量自由度和一个空间协变版本与拉格朗日乘子，可以消除标量模式。本文研究了在4 EGB引力作用下静态球对称黑洞周围薄吸积盘的电磁辐射的物理性质。为此目的，我们假设磁盘是在一个稳定的状态，并在流体动力学和热力学平衡，使发射的电磁辐射是一个黑体光谱。详细研究了4 EGB引力场中高斯-邦纳耦合常数$α$对盘的能流、温度分布和电磁波谱的影响。结果表明，随着参数$α$的增大，吸积盘的能流、温度分布和电磁波谱均增大。此外，我们还发现吸积效率随参数$α$的增大而增大。结果表明，在4 EGB引力下，对于正的$α$，静态球对称黑洞周围的薄吸积盘比相同质量的Schwarzschild黑洞周围的薄吸积盘更热、更亮、更有效;而对于负的$α$，薄吸积盘比相同质量的Schwarzschild黑洞周围的薄吸积盘更冷、更亮、更有效.

英文摘要：

Recently a novel four-dimensional Einstein-Gauss-Bonnet (4EGB) theory of gravity was proposed by Glavan and Lin [D. Glavan and C. Lin, Phys. Rev. Lett. 124, 081301 (2020)] which includes a regularized Gauss-Bonnet term by using the re-scaling of the Gauss-Bonnet coupling constant $α\to α/(D-4)$ in the limit $D\to 4$. This theory also has been reformulated to a specific class of the Horndeski theory with an additional scalar degree of freedom and to a spatial covariant version with a Lagrangian multiplier that can eliminate the scalar mode. Here we study the physical properties of the electromagnetic radiation emitted from a thin accretion disk around the static spherically symmetric black hole in the 4EGB gravity. For this purpose, we assume the disk is in a steady-state and in hydrodynamic and thermodynamic equilibrium so that the emitted electromagnetic radiation is a black body spectrum. We study in detail the effects of the Gauss-Bonnet coupling constant $α$ in 4EGB gravity on the energy flux, temperature distribution, and electromagnetic spectrum of the disk. It is shown that with the increases of the parameter $α$, the energy flux, temperature distribution, and electromagnetic spectrum of the accretion disk all increase. Besides, we also show that the accretion efficiency increases as the growth of the parameter $α$. Our results indicate that the thin accretion disk around the static spherically symmetric black hole in the 4EGB gravity is hotter, more luminosity, and more efficient than that around a Schwarzschild black hole with the same mass for a positive $α$, while it is cooler, less luminosity, and less efficient for a negative $α$.

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