Pair Creation Process In Vacuum Induced By Bound-continuum Interactions

Quantum electrodynamics is one of the most accurate physics theories to describe the interaction of electromagnetism and matter.The quantum vacuum decay to produce particle-antiparticle in a strong electromagnetic field is one of the basic predictions of quantum electrodynamics.With the development of laser technology,intensity of the electromagnetic field generated in laboratory is close to the threshold of causing the vacuum decay.Thus,it is also urgent to study the process of particle-antiparticle creation in the vacuum under the strong electromagnetic field condition.The existing laser technology enables the creation process of particle-pair to be realized mainly by the mechanism of multi-photon absorption.The bound states existed between positive and negative continuous states can effectively reduce the required energy for photons.In this dissertation,the role of bound states in the vacuum decay is studied by using the theory of strong field quantum electrodynamics and the computational quantum field theory method which is based on the numerical solution to the Dirac equation.The main content of this dissertation and the progress of the research are as follows:First,this dissertation investigates the role of the locality of bound states in the process of particle-pair creation.By studying the process of particle-pair creation under the influence of a potential well and a laser field,it is found that the width of locality for bound states can be changed while tuning the width of the potential well.The process of particle-pair creation can also be enhanced by narrowing bound state extension in position space.It is concluded that the more bound state is localized in the position space,the wider its extension will be in momentum space,which can enhance the bound-continuum interaction in the creation process.So the decay from the vacuum state to bound state is enhanced.Second,this dissertation investigates the role of the dynamic Stark effect in the process of particle-pair creation,especially the role of the energy shift of bound state under the external field on energy conservation and the required of photon threshold in the process of the vacuum decay.By studying positron energy spectrum under the interaction between high intensity laser and bound state,it is found that the energy shift of bound state can cause the positron energy spectrum to shift,and it is concluded that the energy shift of bound state induced by high intensity laser is very important in correctly predicting the created positron energy spectrum.By studying the positron energy spectrum where the laser frequency is tuned to the bound state energy difference,the resonance associated with electron Rabi oscillations is transferred to the created positrons,leading to new splitting peaks in their energy spectrum which is similar to the Autler-Townes split phenomenon in ionization process.Third,in order to reveal the role of the Pauli exclusion principle on the process of particle-pair creation in the presence the Rabi oscillations caused by multiple bound state resonance,this dissertation studies an ionization model that permits us analytical solutions.It is concluded that the Pauli exclusion principle in multi-particle resonance ionization is only a transient effect and its dynamical impact decreases with the increase of the Rabi frequency.Due to mutually competing mechanisms,this principle can enhance the ionization probability,while at the same time it also decreases the probability for double ionization.We plan to associate the ionization process with the pair creation process,and hope that the similar phenomena can be observed in the future studies.