| The discovery of black hole thermodynamics now offers the excitement in physical fundamental theory.In 1983,Hawking and Page proposed the concept of black hole phase transition,and their calculation showed the phase transition of charged AdS black hole,which is called Hawking-Page phase transition.In the past few years,by treating the cosmological constant as the pressure,the complete analogy between the Van der Waals(vdW)fluid and charged AdS black hole was found.Moreover,The discovery of black hole thermodynamics has helped us to know the nature of gravity.Physicists generally believe that the space is emergent which means gravity may not be a fundamental interaction but an emergent phenomenon.In 2012,Padmanabhan argued that the spatial expansion of our universe is due to the difference between the surface degree of freedom(DOF)and the bulk DOF in the region of emerged space,and he obtained Friedmann equations of Einstein gravity.In this paper,we will mainly discuss the phase transition of black hole and emergence of cosmic space,as well as the work we have made in these topics.On the one hand,by proposing a generalized specif ic volume,we restudy the P-V criticality of charged AdS black holes in the extended phase space.The results show that most of the previous conclusions can be generalized without change,but the ratio ?ρcshould be 3 ?α/16 in general case.Further research on the thermodynamical phase transition of black hole leads us to a natural interpretation of our assumption,and more black hole properties can be generalized.Finally,we study the number density for charged AdS black hole in higher dimensions,the results show the necessity of our assumption.On the other hand,motivated by Padmanabhan’s idea that the spatial expansion of our universe is due to the difference between the surface DOF and the bulk DOF in the region of emerged space,we firstly study the de Sitter universe from emergence of space.After that— II —we investigate the universes in general cases and then narrow down our discussions into one of them with a detailed discussion of the possibility in describing our real universe classically.Furthermore,an estimated value of cosmological constant can be derived from our model,the comparison with experiments is also presented.The results show the validity of our model.Moreover,we found that the horizon problem and flatness problem can be avoided in our model.While,there is a serious problem in our model,namely the nonexistence of deceleration phase.To solve this problem,our model needs modification. |
