Radiative Properties And Resonance Interaction Of Atoms In Topological Defect Spacetime

In the interaction of atoms with electromagnetic field,there can occur the atomic radiation phenomena and the interatomic interaction.The radiation phenomena usually include spontaneous emission,stimulated emission and stimulated absorption,and the interatomic interaction can be attractive or repulsive.In fact,these important quantum effects are not inherent for atoms.A lot of relevant researches have shown that these physical processes can be attributed to the combined effects of quantum fluctuations and radiation reaction.Meanwhile,we learn that some factors can have an appreciable impact on these quantum processes,such as the state of atoms and quantum fields,the atomic motion state,boundary condition of quantum fields,spacetime background,etc.With the development of quantum field theory in curved spacetime and quantum gravi-ty,the investigations of some important quantum processes in flat spacetime have been increasingly extended to the background of curved spacetimes,such as Schwarzschild spacetime,de Sitter spacetime,Kerr spacetime.On the other hand,topological defects formed at symmetry breaking phase transitions play an important role in Cosmology,Condensed matter physics,Atomic and molecular physics and other fields.Many pre-vious works have manifested that topological defects have some unusual properties and can significantly influence some physical processes.In particular,topological defects in some cosmological systems or condensed matter systems can induce directly or e-quivalently gravitational effects.According to general relativity,gravity is described by geometry,that is curved spacetime.This paper intends to extend the investigation for the relevant properties of the atom-field interaction system in Minkowski space-time to the one in some simple topological defect spacetimes,such as the cosmic string spacetime,the global monopole spacetime and the cosmic dispiration spacetime.In the latter two spacetimes,we consider a toy model of the interaction of atoms with a quantum scalar field,while in the first spacetime we consider the actual interaction of atoms with a quantum electromagnetic field.Specifically,using the formalism of DDC we separately calculate the contributions of free quantum fluctuations and radi-ation reaction to two important physical quantities:the atomic transition rates and the interatomic interaction energy.As is well-known,entanglement is an important and basic concept in quantum mechanics and it is absent in any classical theory.An entangled state of a compos-ite system is defined as a state that cannot be factorized into a product of states of its component systems.Some scholars are devoted to studying the measurement and cri-terion of entanglement,and also the entanglement dynamics and evolution behaviours of quantum systems in different environments.In particular,entanglement has increas-ingly attracted a great of interest and attentions since it occupies a fundamental status in quantum communication,quantum cryptography and quantum computation and other subfields in quantum information science.Concerning the atomic radiative properties and interaction,the investigations of a single atom have been extended to the case of the entangled atoms.In view of the significance of quantum entanglement,in our work we consider the relevant properties of two entangled atoms in the cosmic string spacetime.Our results indicate that the transition rates and the interaction energy of atoms depend deeply on the atomic position and the atomic polarizability with respect to the defect source,and the intrinsic parameter of topological defects.In general,with the increase of the distance between the atoms and the defect source,the transition rates and the interaction energy of atoms oscillate around their corresponding results of the Minkowski spacetime,and meanwhile the amplitude of oscillation gradually decreas-es.Concerning the atomic radiative properties,for static atoms coupled to vacuum quantum field,only the spontaneous emission process can occur,while for static atoms coupled to thermal reservoir,both the stimulated emission and stimulated absorption processes can occur.Concerning the interatomic interaction,the value of resonance energy between the entangled atoms can be positive or negative,and is only attribut-ed to the contribution of radiation reaction.Through comparison with the case of the Minkowski spacetime,we find that the presence of topological defects modifies both the contributions of quantum fluctuations and radiation reaction to the relevant physi-cal quantities.By adjusting the relevant parameters,the atomic transition rates and the interatomic resonance energy can be enhanced or weakened at different degrees.This means that the presence of topological defects can significantly influence the atomic radiative properties and the interatomic interaction.In addition,we also compare the differences and similarities between the atomic relevant properties in different cases for a certain factor,for example,different types of topological defects,different types of atom-field couplings,different types of interactions between the quantum field and the gravitational field,different states of atoms and fields.Without doubt,these compar-isons and analyses are very helpful for us to deepen our cognition and understanding of these physical processes.