Formation of black hole and emission of gravitational waves

Numerical simulations were performed for the formation process of rotating black holes. It is suggested that Kerr black holes are formed for wide ranges of initial parameters. The nature of gravitational waves from a test particle falling into a Kerr black hole as well as the development of 3D numerical relativity for the coalescing binary neutron stars are discussed.     

黑洞照亮宇宙——银河系中心黑洞及其物理意义

2020年度诺贝尔物理学奖颁发给为黑洞和超大质量致密天体做出突出贡献的三位科学家,他们分别从理论和观测上提供了令人信服的证明和证据。他们的工作打开了理解宇宙中大质量天体命运的窗口。人们普遍相信超大质量黑洞存在于每一个星系的中心,是这些黑洞照亮了再电离时期的宇宙,也是它们为揭开宇宙膨胀历史、暗能量宇宙演化性质、纳赫兹低频引力波等诸多谜团提供了十分强大的工具。预计未来5年内,反响映射和GRAVITY/VLTI联合观测将在以黑洞研究为支撑的领域取得重大进展。     

Gravitational Lensing by Charged Black Holes

We formulate the lensing effects of a spherically symmetric electrically charged black hole using thin lens equations. The charged black hole leads to three images and could lead to three Einstein rings provided the parameters such as the mass, charge and the distances satisfy certain constraints. We have computed the exact positions of images and magnification properties for a super-massive black hole with electric charge.     

Expanding the Area of Gravitational Entropy

I describe how gravitational entropy is intimately connected with the concept of gravitational heat, expressed as the difference between the total and free energies of a given gravitational system. From this perspective one can compute these thermodyanmic quantities in settings that go considerably beyond Bekenstein's original insight that the area of a black hole event horizon can be identified with thermodynamic entropy. The settings include the outsides of cosmological horizons and spacetimes with NUT charge. However the interpretation of gravitational entropy in these broader contexts remains to be understood.     

De Broglie Matter Waves from the Linearized Einstein Field Equations

We suggest a connection between matter waves and gravitational waves. We find solutions of the linearized Einstein field equations in the form of de Broglie waves. These therefore acquire a new geometrical meaning.     

Gravity/CFT correspondence for three-dimensional Einstein gravity with a conformal scalar field

We study the three-dimensional Einstein gravity conformally coupled to a scalar field. Solutions of this theory are geometries with vanishing scalar curvature. We consider solutions with a constant scalar field which corresponds to an infinite Newton?s constant. There is a class of solutions with possible curvature singularities which asymptotic symmetries are given by two copies of the Virasoro algebra. We argue that the central charge of the corresponding CFT is infinite. Furthermore, we construct a family of Schwarzschild solutions which can be conformally mapped to the Martínez–Zanelli solution of Einstein?s equations with a negative cosmological constant coupled to conformal scalar field.     

Time Delay in Black Hole Gravitational Lensing as a Distance Estimator

We calculate the time delay between different relativistic images formed by black hole gravitational lensing in the strong field limit. For spherically symmetric black holes, it turns out that the time delay between the first two images is proportional to the minimum impact angle. Their ratio gives a very interesting and precise measure of the distance of the black hole. Moreover, using also the separation between the images and their luminosity ratio, it is possible to extract the mass of the black hole. The time delay for the black hole at the center of our Galaxy is just few minutes, but for supermassive black holes with M=10⁸ ÷10⁹ in the neighbourhood of the Local Group the time delay amounts to few days, thus being measurable with a good accuracy.     

The gravitational wave symphony of the Universe

The new millennium will see the upcoming of several ground-based interferometric gravitational wave antennas. Within the next decade a space-based antenna may also begin to observe the distant Universe. These gravitational wave detectors will together operate as a network taking data continuously for several years, watching the transient and continuous phenomena occurring in the deep cores of astronomical objects and dense environs of the early Universe where gravity was extremely strong and highly nonlinear. The network will listen to the waves from rapidly spinning non-axisymmetric neutron stars, normal modes of black holes, binary black hole inspiral and merger, phase transitions in the early Universe, quantum fluctuations resulting in a characteristic background in the early Universe. The gravitational wave antennas will open a new window to observe the dark Universe unreachable via other channels of astronomical observations.     

On Thermodynamical Relation Between Rotating Charged BTZ Black Holes and Effective String Theory

In this paper we study the first law of thermodynamics for the （2＋1）-dimensional rotating charged BTZ black hole considering a pair of thermodynamical systems constructed with the two horizons of this solution. We show that these two systems are similar to the right and left movers of string theory and that the temperature associated with the black hole is the harmonic mean of the temperatures associated with these two systems.