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arXiv 2411.00565gr-qc
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具有非对称真空的标量毛发黑洞周围试验粒子的测地线运动

Geodesic Motion of Test Particles around the Scalar Hairy Black Holes with Asymmetric Vacua

Hongyu Chen, Wei Fan, Xiao Yan Chew

AI总结:

本研究针对具有非对称真空的标量毛发黑洞,通过分析有效势探究其附近有质量试验粒子与光子的测地线运动,明确了圆轨道特性、光子球位置及零测地线分类与史瓦西黑洞的差异。

摘要:

渐近平坦毛发黑洞(HBH)与史瓦西黑洞相比可展现出不同的特征,这是因为通过将爱因斯坦引力与具有非对称真空的标量势最小耦合——即假真空$(ϕ=0)$和真真空$(ϕ=ϕ_1)$——规避了无毛定理。本文中,我们通过分析由测地线方程推导得到的有效势,研究了$ϕ_1=0.5$和$ϕ_1=1.0$的HBH附近有质量试验粒子和光子的测地线运动。在固定$ϕ_1$的情况下,当有质量试验粒子的角动量$L$很小时,其有效势单调递增。当$L$增大到临界值时,有效势存在一个拐点,即最内稳定圆轨道(ISCO),在此处试验粒子仍能以最小半径稳定保持在圆轨道上,既不会被HBH吞噬也不会逃逸至无穷远。当$L$超过临界值后,有效势存在一个局部极小值和一个局部极大值,分别对应不稳定圆轨道和稳定圆轨道的存在。此外,HBH存在一个不稳定光子球,但其位置与史瓦西黑洞的光子球位置略有偏差。根据光的偏转角,HBH附近的零测地线轨迹也可分为三类:直接类、引力透镜类和光子球类,但其碰撞参数值与史瓦西黑洞的碰撞参数值相比可能存在显著差异。

英文摘要:

An asymptotically flat hairy black hole (HBH) can exhibit distinct characteristics when compared to the Schwarzschild black hole, due to the evasion of no-hair theorem by minimally coupling the Einstein gravity with a scalar potential which possesses asymmetric vacua, i.e, a false vacuum $(ϕ=0)$ and a true vacuum $(ϕ=ϕ_1)$. In this paper, we investigate the geodesic motion of both massive test particles and photons in the vicinity of HBH with $ϕ_1=0.5$ and $ϕ_1=1.0$ by analyzing their effective potentials derived from the geodesic equation. By fixing $ϕ_1$, the effective potential of a massive test particle increases monotonically when its angular momentum $L$ is very small. When $L$ increases to a critical value, the effective potential possesses an inflection point which is known as the innermost stable of circular orbit (ISCO), where the test particle can still remain stable in a circular orbit with a minimal radius without being absorbed by the HBH or fleeing to infinity. Beyond the critical value of $L$, the effective potential possesses a local minimum and a local maximum, indicating the existence of unstable and stable circular orbits, respectively. Moreover, the HBH possesses an unstable photon sphere but its location slightly deviates from the Schwarzschild black hole. The trajectories of null geodesics in the vicinity of HBH can also be classified into three types, which are the direct, lensing and photon sphere, based on the deflection angle of light, but the values of impact parameters can vary significantly than the Schwarzschild black hole.

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