Testing The Weak Cosmic Censorship Conjecture With Gedanken Experiment

The weak cosmic censorship conjecture has become one of the cornerstones of black hole physics,and it has a deep connection with the laws of black hole thermodynamics.The conjecture might be proved to be true,but the gedanken experiment can help us to understand it better and bring new insight on the relation between the weak cosmic censorship conjecture and the laws of black hole thermodynamics.Besides,it is also important to explore what it is that makes the conjecture to be true.On the other hand,if the final result proves that the weak cosmic censorship conjecture can indeed be violated,this might provide us the possibility to access quantum regime of gravity inside black holes.In this thesis,we try to destroy the event horizon of several black holes with test particles and test scalar field,and investigate the validity of the weak cosmic censorship conjecture for these black holes.Motivated by the previous study about the weak cosmic censorship conjecture for Kerr-Taub-NUT black hole and the recent researches of black hole thermodynamics with NUT charge,we investigate the validity of the weak cosmic censorship conjecture for Kerr-Taub-NUT black holes with a test massive scalar field and a test particle,respectively.For scattering of a scalar field,our result suggests that both extremal and near-extremal Kerr-Taub-NUT black holes cannot be destroyed.For the test particle injection,an extremal black hole cannot be over-spun;while a near-extremal Kerr-TaubNUT black hole can be destroyed.Recent researches of the novel 4D Einstein-Gauss-Bonnet gravity have attracted great attention.We investigate the validity of the weak cosmic censorship conjecture for a novel 4D charged Einstein-Gauss-Bonnet black hole with a test charged scalar field and a test charged particle respectively.For the test charged field scattering process,we find that both extremal and near-extremal black holes cannot be overcharged.For the test charged particle injection,to first order,an extremal black hole cannot be overcharged while a near-extremal 4D charged Einstein-Gauss-Bonnet black hole can be destroyed.To second order,however,both the extremal and near-extremal 4D charged Einstein-Gauss-Bonnet black holes can be overcharged for a positive Gauss-Bonnet coupling constant;for a negative Gauss-Bonnet coupling constant,an extremal black hole cannot be overcharged and the validity of the weak cosmic censorship conjecture for a near-extremal black hole depends on the Gauss-Bonnet coupling constant.The destruction of the event horizon of a nonsingular black hole,which is not prevented by the weak cosmic censorship conjecture,might provide us the possibility to access quantum regime of gravity inside black hole.We investigate the possibility of overspinning a nonsingular rotating quantum-corrected black hole by a test particle and a scalar field in this paper,and analyse the effect of the quantum parameter on the destruction of the event horizon.For the test particle injection,both the extremal and near-extremal black holes cannot be overspun due to the existence of the quantum parameter.And the larger the quantum parameter,the harder the black hole to be overspun.It seems that the quantum parameter acts as a protector to prevent the black hole to be destroyed.However,for the test scalar field scattering,both the extremal and nearextremal black holes can be destroyed.Due to the loop quantum gravity correction,the angular velocity of the extremal black hole shifts from that of the extremal Kerr black hole.This provides a small range of wave modes to destroy the event horizon of the quantum-corrected black hole.There is a claim that a series of black holes can be generically overspun by test fields,which might indicate the failure of the predictability of classical gravity theory.Motivated by this,we investigate the validity of the weak cosmic censorship conjecture for Kerr-Sen black holes by scattering of a test scalar field.Our results suggest that both the extremal and near-extremal Kerr-Sen black holes cannot be destroyed.Our results are inconsistent with those of Düztas’ work that the weak cosmic censorship conjecture for the Kerr-Sen black hole can be violated.We provide possible solutions to the contradiction by arguing,for black holes far from extremal,Düztas’ choice of energy violating Hawking’s area increasing theorem.