Gravitational Effect In The Spacetime Of Stringy Black Hole And Black Hole Surrounded By Quintessence-Like Matter

The gravitational field of a black hole is so strong that even the light inside the horizon can not escape. Therefore, the black hole can not be observed directly, but we can use some indirect ways, such as Hawking radiation, corpuscular stream, black hole accretion and gravitational lensing, etc, to detect black hole. This thesis investigates black hole from three aspects:the orbital dynamics in black hole spacetime, the accretion of quintessence-like matter onto a black hole and the strong gravitational lensing in black hole.In the first chapter, we briefly introduce the formation and the classification of black hole, the scalar field model of dark energy and the fundamental knowledge of the gravitational lensing.In the second chapter, combining the effective potential, the orbital dynamics of the gravitational field of Stringy black hole is investigated by means of the phase plane analysis method. We give the general relativistic equations of motion in the gravitational field of Stringy black hole, and discuss the stability and types of the test particles’orbits. Our results show that when the angular momentum b≤4.3887, the test particles will fall into black hole, and at rmin= 5.47422, the test particles have an innermost stable circular orbit.In the third chapter, we study the accretion of dark energy onto a Stringy electrically charged black hole, and derive that the location of the critical point where the speed of flow is equal to the speed of sound lies inside the event horizon. Taking linearized model of dark energy and Chaplygin gas model into account, we get the expression for the mass-change of the black hole accreting the two solvable models of dark energy, respectively. By analysis, we find that when a Stringy electrically charged black hole accretes the phantom-like dark energy (meet the condition:p+p< 0), its mass will decrease. But when it accretes the quintessence-like dark energy (meet the condition:p+p> 0), its mass increases.In the fourth and fifth chapters, applying the strong field limit approach, we investigate the strong gravitational lensing in Stringy black hole and a black hole with deficit solid angle (DSA) surrounded by quintessence-like matter (QM). Assuming that the two types of black holes are all the supermassive object at the galactic center, we estimate the numerical values of the strong field limit coefficients and the observables, respectively. The results show that, in the Stringy black hole, the angular position 0∞ increases and the relative magnitudes Rm decreases with the increasing of the parameter a. In the spacetime of the black hole with DSA and surrounded by QM, the deflection angle and the strong field limit coefficients all increase faster and faster as e2 or po increases. Moreover, comparing our results with Schwarzschild black hole, we find that the black hole surrounded by QM has smaller relative magnitudes, and when the equation of state parameter is different, the variations of the angular position and the angular separation are also different. Therefore, the strong gravitational lensing can be used to distinguish Stringy black hole and the black hole with a DSA and surrounded by QM from Schwarzschild black hole, and also gives us an alternative way to know better about the two types of black holes.