共查询到20条相似文献,搜索用时 140 毫秒
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在同时考虑吸积和Blandford-Znajek过程的条件下,详细讨论了吸积盘(包括薄盘和厚盘)中心黑洞的自转角速度Ωh的演化特征.结果表明,当黑洞的无量纲角动量a*演化到某一临界时,Ωh对时间的变化率由正变负,从而推断在顺行吸积过程事Ωh先增后减,演化非单调,因而存在一个极大值.并指出黑洞的无量纲角动理a*比黑洞的角动量J和自转角速度Ωh更适合描写吸积盘中心黑洞自转状态的演
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对具有双旋转参数的5维时空中,黑洞视界的热力学参量与宇宙视界的热力学参量进行了研究 .发现宇宙视界的熵能写为Cardy-Verlinde公式的形式,而黑洞视界的熵要写成Cardy-Verl inde公式的形式,必须用Abbott 和Deser的方法,计算具有双旋转参数5维黑洞的质量.通过研究,给出了具有双旋转参数5维黑洞各热力学参量之间满足的关系式,即热力学第一定律的微分式.
关键词:
Cardy-Verlinde公式
Casimir能量
de Sitter时空 相似文献
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重点讨论了薄盘吸积与渐近安全(asymptotically safe,AS)引力修正参数对黑洞阴影和光环的影响.对于薄盘吸积,黑洞的暗区就是黑洞的阴影,而明亮的光环则是由直接像、透镜环和光子环组成的.对于吸积盘辐射源比强度,考虑了3个不同辐射轮廓模型.对辐射起始于最内圆轨道的二阶衰减函数模型,直接像、透镜环和光子环可以明显区分.直接像对黑洞光环亮度贡献最大,透镜环对光环亮度贡献很小,而光子环的贡献几乎可以忽略,且对应观测强度的峰值随AS引力参数的增加而减小,即对应光环亮度随修正参数的增大而变暗.对于辐射起始于光子球半径的三阶衰减函数模型,透镜环和光子环叠加在直接像上,使观测强度出现新的极值.这一极值随AS引力修正参数的增加而增加,且使得黑洞光环的亮度更亮.对辐射起始于事件视界的反三角衰减函数模型,透镜环和光子环在直接像上的叠加范围更大,观测到的光环更宽,且AS引力参数值越小,透镜环和光子环越难区分,黑洞光环的亮度越大.总之,研究表明,黑洞阴影半径的大小随AS修正参数的增加而减小,对于不同的AS引力修正参数,辐射源光强度、尤其是观测强度的辐射轮廓存在显著差异,导致黑洞的阴影和亮环明显不同... 相似文献
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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. 相似文献
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考虑到螺旋不稳定性的影响, 提出了一种黑洞磁层的新磁场位形(NCMF). 其中涉及到磁场提取能量的三种机制: (1) Blandford-Znajek (BZ)过程; (2)磁耦合(MC)过程; (3) 通过开磁力线联系吸积盘和天体物理负载,并提取吸积盘的旋转能量新机制(文中称为DL过程). 利用两类等效电路导出上述三种提能机制的功率和力矩的表达式. 结果表明,在新磁场位形中提能功率和效率比未考虑螺旋不稳定性的磁场位形有所增大,新磁场位形导出的非常陡的发射率指数可以拟合XMM-Newton天文卫星对邻近的明亮的Seyfert 1星系MCG-6-30-15的观测结果. 相似文献
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均质旋转面绕旋转轴转动的转动惯量 总被引:3,自引:2,他引:1
根据转动惯量的定义推得任意形状均质旋转面对旋转轴的转动惯量的计算公式,文中讨论了鼓形面、花瓶形面、圆台面、圆锥面、圆柱面等特殊形状均质旋转面对旋转轴的转动惯量. 相似文献
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Shadow images and observed luminosity of the Bardeen black hole surrounded by different accretions 下载免费PDF全文
In this paper, by exploring photon motion in the region near a Bardeen black hole, we studied the shadow and observed properties of the black hole surrounded by various accretion models. We analyzed the changes in shadow imaging and observed luminosity when the relevant physical parameters are changed. For the different spherical accretion backgrounds, we find that the radius of shadow and the position of the photon sphere do not change, but the observed intensity of shadow in the infalling accretion model is significantly lower than that in the static case. We also studied the contribution of the photon rings, lensing rings and direct emission to the total observed flux when the black hole is surrounded by an optically thin disk accretion. Under the different forms of the emission modes, the results show that the observed brightness is mainly determined by direct emission, while the lensing rings will provide a small part of the observed flux, and the flux provided by the photon ring is negligible. By comparing our results with the Schwarzschild spacetime, we find that the existence or change of relevant status parameters will greatly affect the shape and observed intensity of the black hole shadow. These results support the theory that the change of state parameter will affect the spacetime structure, thus affecting the observed features of black hole shadows. 相似文献
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The shadow and observation appearance of black hole surrounded by the dust field in Rastall theory 下载免费PDF全文
Xuan-Ran Zhu 《中国物理 B》2023,32(1):10401-010401
In the context of Rastall gravity, the shadow and observation intensity casted by the new Kiselev-like black hole with dust field have been numerically investigated. In this system, the Rastall parameter and surrounding dust field structure parameter have considerable consequences on the geometric structure of spacetime. Considering the photon trajectories near the black hole, we investigate the variation of the radii of photon sphere, event horizon and black hole shadow under the different related parameters. Furthermore, taking into account two different spherically symmetric accretion models as the only background light source, we also studied the observed luminosity and intensity of black holes. For the both spherical accretions background, the results show that the decrease or increase of the observed luminosity depends on the value range of relevant parameters, and the promotion effect is far less obvious than the attenuation effect on the observed intensity. One can find that the inner shadow region and outer bright region of the black hole wrapped by infalling accretion are significantly darker than those of the static model, which is closely related to the Doppler effect. In addition, the size of the shadow and the position of the photon sphere are always the same in the two accretion models, which means that the black hole shadow depend only on the geometry of spacetime, while the observation luminosity is affected by the form of accretion material and the related spacetime structure. 相似文献
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Two Mechanisms for Extracting Energy and Angular Momentum from a Rotating Black Hole 总被引:1,自引:0,他引:1
Two mechanisms of extracting energy and angular momentum from a rotating black hole, the Blandford-Znajek (BZ) process and magnetic coupling (MC) of a rotating black hole (BH) with the surrounding accretion disk, are discussed in detail by using a modified equivalent circuit. We obtain the same value for the BZ power as given by Lee. The strength of the power and torque produced by the rotating BH in the BZ process are compared with those in MC process. In addition, entropy production on the BH horizon due to the BZ process and that due to MC process are compared and discussed also by using the modified equivalent circuit. 相似文献
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The general-relativistic effects of an extreme Reissner-Nordström black hole on the flux of radiation emitted by a hot spot orbiting the hole with a thin accretion disk are investigated. The light curves, the redshift factor, and the solid angle against the spot orbit position are given. The results are then compared with those of a spot orbiting a Schwarzschild black hole. 相似文献
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Circular geodesics and accretion disk in the spacetime of a black hole including global monopole 下载免费PDF全文
We study circular time-like geodesics in the spacetime of a black hole including global monopole. We show that when the range of parameter changed the properties of the circular geodesics and the radiation of accretion disks are different. It follows that the properties of the accretion disk around black hole including global monopole can be different from that of a disk around Schwarzschild black hole. 相似文献
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Valerio Bozza 《General Relativity and Gravitation》2010,42(9):2269-2300
We review the theoretical aspects of gravitational lensing by black holes, and discuss the perspectives for realistic observations.
We will first treat lensing by spherically symmetric black holes, in which the formation of infinite sequences of higher order
images emerges in the clearest way. We will then consider the effects of the spin of the black hole, with the formation of
giant higher order caustics and multiple images. Finally, we will consider the perspectives for observations of black hole
lensing, from the detection of secondary images of stellar sources and spots on the accretion disk to the interpretation of
iron K-lines and direct imaging of the shadow of the black hole. 相似文献
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We study the accretion process in the thin disk around a rotating non-Kerr black hole with a deformed parameter and an unbound rotation parameter. Our results show that the presence of the deformed parameter ? modifies the standard properties of the disk. For the case in which the black hole is more oblate than a Kerr black hole, the larger deviation leads to the smaller energy flux, the lower radiation temperature and the fainter spectra luminosity in the disk. For the black hole with positive deformed parameter, we find that the effect of the deformed parameter on the disk becomes more complicated. It depends not only on the rotation direction of the black hole and the orbit particles, but also on the sign of the difference between the deformed parameter ? and a certain critical value ?c. These significant features in the mass accretion process may provide a possibility to test the no-hair theorem in the strong-field regime in future astronomical observations. 相似文献
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Here we consider accelerating and rotating charged Plebanski-Demianski (PD) class of black hole metric as a particle accelerator. We obtain the geodesic motions (timelike, null and spacelike) of particles in a non-equatorial plane around the PD black hole. We find the effective potential, energy, angular momentum, impact parameters, and discuss the circular orbit. We study the center of mass energy of two neutral particles falling from infinity to near the non-extremal horizons (event and Cauchy horizons), extremal horizon, accelerating horizons, and near the center of the PD black hole. Also, we study the collision of a particle and a massless photon. Then we find the center of mass energy due to the collision of two massless photons in the PD black hole background. We compute the redshift and blueshift of the emitted photons by massive particles while light signal travels along null geodesics towards the observer located far away from the source. We study the Penrose process, which occurs within the ergosphere, and examines the particle’s motion with its implications. Here, we analyze the PD black hole shadow’s apparent shape, which forms far away from the black hole. We study the possible visibility of the PD black hole through photon’s shadow and energy emission rate. We also investigate the effect on the shadow of the PD black hole in plasma for a distant observer. We study the strong gravitational lensing by PD black hole. Finally, we analyze the deflection angle, lens equation, position, magnification, Einstein ring and observables by taking the supermassive PD black hole in the Galaxy’s center. 相似文献
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In this paper, we study the shadows and observational appearance of the Ayón-Beato-García (ABG) black hole, which is surrounded by a thin disk accretion. For a four-dimensional ABG black hole, as the charge q increases, the event horizon r+, radius rp and impact parameter bp of the photon sphere decrease, while the maximum value of effective potential Veff increases. However, as the term γ associated with nonlinear electrodynamics increases, the related physical quantities r+, rp and bp increase, but the maximum value of Veff decreases. When the light ray reaches the vicinity of the ABG black hole, one can observe the trajectories of the light rays appearing as three types, i.e., direct emission, lens ring and photon ring. Furthermore, the shadows and the observational appearance of the ABG black hole are studied. The results show that the charge q and the term γ have a great influence on the shape and intensity of the black hole shadow. When the relevant state parameters change or the emission model changes, it can be argued that it is the direct emission that plays a decisive role in the total observed intensity of the ABG black hole, while the contribution of the lens ring to the total observed intensity is small and the photon ring makes almost no contribution. 相似文献
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When a star is tidally disrupted by a supermassive black hole (SMBH), the streams of liberated gas form an accretion disk after their return to pericenter. We demonstrate that Lense-Thirring precession in the spacetime around a rotating SMBH can produce significant time evolution of the disk angular momentum vector, due to both the periodic precession of the disk and the nonperiodic, differential precession of the bound debris streams. Jet precession and periodic modulation of disk luminosity are possible consequences. The persistence of the jetted x-ray emission in the Swift J164449.3+573451 flare suggests that the jet axis was aligned with the spin axis of the SMBH during this event. 相似文献