Entanglement Dynamics For Static Two-level Atoms In Cosmic String Spacetime

According to Einstein’s general relativity,matter curves spacetime.And the curvature of spacetime in turn will render vacuum fluctuations of quantum fields in curved spacetime to exhibit properties different from those in flat spacetime,so as to affect the behavior of entanglement dynamics of atoms coupled with quantum fluctuations of fields in vacuum.Cosmic strings are topological defects that may have been created in the early Universe during phase transitions.The cosmic string spacetime is a kind of simple curved spacetime,which can be regarded as a flat spacetime with a planar angle deficit.The simplest cosmic string spacetime is that of a static,straight and infinitely thin cosmic string.In this thesis,we study,in the framework of open quantum systems,the entanglement dynamics of two static atoms coupled with a bath of fluctuating massless scalar fields in vacuum in the cosmic string spacetime.Three different alignments of atoms,i.e.parallel,vertical,and symmetric alignments with respect to the cosmic string are considered.We focus on how the phenomena of entanglement degradation and generation are influenced by the cosmic string,and find that they are crucially dependent on the atom-string distance r,the interatomic separation L,and the parameter v that characterizes the nontrivial topology of the cosmic string.When the two atoms are initially in a maximally entangled state,the entanglement characterized by concurrence decays monotonically when the atoms are aligned parallel to or symmetrically to the cosmic string,while the destroyed entanglement can be revived when the two atoms are aligned vertically to the string,which cannot happen in the Minkowski spacetime.When the symmetrically aligned two-atom system is initially in the antisymmetric state,the lifetime of entanglement can be significantly enhanced as v increases.For two initially separable atoms,when the distance between two atoms is large compared to the transition wavelength,entanglement generation cannot happen in the Minkowski spacetime,while it can be achieved in the cosmic string spacetime at certain positions.