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中国物理学会期刊

Kiselev黑洞的热力学性质和物质吸积特性

CSTR: 32037.14.aps.68.20182055

Thermodynamic properties and matter accretion properties of Kiselev black hole

CSTR: 32037.14.aps.68.20182055
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  • 本文考虑带有黑洞视界和宇宙视界的Kiselev时空. 研究以黑洞视界和宇宙视界为边界的系统的热力学性质. 统一地给出了两个系统的热力学第一定律; 在黑洞视界半径远小于宇宙视界半径的情况下, 近似地计算了通过宇宙视界和黑洞视界的热能. 然后, 探讨Kiselev时空的物质吸积特性. 在吸积能量密度正比于背景 能量密度的条件下给出黑洞的吸积率, 讨论了黑洞吸积率与暗能量态方程参数的关系.

     

    Kiselev black hole possesses the two horizons, i.e. the inner horizon and outer horizon. In some cases, the so-called outer horizon of black hole is actually a cosmic horizon. In this paper, Kiselev space-time with black hole horizon and cosmic horizon is considered. The radius of black hole horizon and the radius of cosmic horizon are approximately obtained to be r_\rm B \approx 2M \left 1 + \left(2M/\lambda\right)^-(3w_\rm \rm q+1) \right and r_\rm C \approx \lambda + \dfrac2M 3w_\rm \rm q+1 with M \ll \lambda and w_\rm q a parameter. The energy density of the Kiselev spacetime near the cosmic horizon is approximately proportional to w_\rm q, so the energy densities with some different w_\rm q have the same order of magnitude in the range -1<w_\rm q < - 1/3. Near the black hole horizon, it increases rapidly with the increase of w_\rm q.  The thermodynamic properties of the systems with black hole horizon and cosmic horizon as boundary are studied. The first law of thermodynamics for the two systems is given in a unified way. Similarly, Smarr relation for the mass of Kiselev black hole is also obtained. For M \ll \lambda , the work done by the fluid on the cosmic horizon and the thermal energy flux flowing into the cosmic horizon of Kiselev spacetime are calculated approximately. In the range of -1 < w_\rm q < - 1/3 , the thermal energy always flows out of the cosmic horizon. The work done by the fluid on the black hole horizon is much smaller than the change in the energy of black hole, \Delta w_\rm B \ll \Delta r_\rm B. This indicates that the energy increase of black hole comes mainly from the thermal energy flowing into the black hole through its outer horizon. The problem of accreting the pressureless fluid into Kiselev black hole is discussed. One can find that there are the zero gravity surfaces between the black hole horizon and cosmic horizon of Kiselev spacetime, the radii of which increase with the decrease of w_\rm q. For w_\rm q=-\dfrac23 and w_\rm q=-1, the accretion radii of Kiselev black hole are respectively determined to be r_0 \approx 1.6 \times 10^4 (l.y.) and r_0 \approx 1.2 \times 10^6 (l.y.). On condition that the accretion energy density is proportional to the background energy density, \rho_\rm mB = \eta_\rm B \rho_\rm B with \eta_\rm B being a proportionality coefficient, the accretion rate of Kiselev black hole is given as \chi_\rm B = - \dfrac3 \eta_\rm B w_\rm q 2 \left(\dfrac2M\lambda\right)^-(3w_\rm q + 1). For w_\rm q= - 2/3 , the accretion rate of the black hole takes its maximum \chi_\rm max \approx 1.2 \times 10^- 6 \eta_\rm B ; for w_\rm q= - 1, the accretion rate takes its minimum \chi_ \rm min \approx 1.2 \times 10 ^ -8 \eta_\rm B . On the assumption that \eta_\rm B changes slowly enough with w_\rm q, the accretion rate of Kiselev black hole increases with the increase of w_\rm q.

     

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