Creation and annihilation phenomena of electron and positron pairs in an oscillating field

The combination of an oscillating and a static field is used to study the creation and annihilation phenomena during the pair creation process. The time evolution, spatial density and momentum distribution of the created particles for a fermionic system are presented, which demonstrate that with the increasing static field intensity, the number of the created particles experiences a distinguishable decrease in every period of the oscillating field, which is caused by the annihilation phenomena between the created electrons and positrons.     

Photon Decays in the Radiation-Dominated Universe: Scalar Electrodynamics

The effect of the creation of an arbitrary number of massive pairs by a photon in the spatially flat model of the radiation-dominated Universe is considered. The process added-up probability is calculated within the framework of scalar quantum electrodynamics conformally related to the metric of a curved spacetime. The rate of photon decay in the radiation-dominated universe as well as the mean number of the created particles have been found. Comparison of the rate of the pair creation in the photon decays with the rate of the pair creation in the photon-photon collisions which take place in the Minkowski spacetime has been carried out. The estimates having been made show the number density of the particles created in the processes of the photon decays in the radiation-dominated Universe to be by a factor of 10³⁰ higher than the number density of the particles created from the vacuum of the free scalar field by the gravitational background.     

Particle creation from vacuum in homogeneous isotropic models of the Universe

Particle creation in Friedman models of the open, closed, and quasi-Euclidean types is considered. The new method of calculation of probabilities of pair creation from vacuum by nonstationary external gravitational field is developed. This method is based on the diagonalization of the energy operator with the help of time-dependent canonical transformations. Finite numerical estimates for the densities of created particles and antiparticles are obtained both for early and modern stages of the evolution of the Universe.     

Creation dynamics of bound States in supercritical fields

Using space-time resolved solutions to relativistic quantum field theory, we analyze the electron-positron creation process from vacuum in the long-time regime in which multiple pairs are produced. We find that for a supercritical potential of finite extension, the time dependence of the production rate of pairs is described by four distinct regimes that have their direct counterparts in the time evolved spatial density of the particles. These regimes include the shape-invariant birth process, an entanglement-induced reduction of interference, a recurrent Pauli suppression of pair production induced by electron-potential scattering, and finally a production halt associated with a population of supercritical and a partial population of subcritical bound states.     

Radiation from electrons in graphene in strong electric field

We study the interaction of electrons in graphene with the quantized electromagnetic field in the presence of an applied uniform electric field using the Dirac model of graphene. Electronic states are represented by exact solutions of the Dirac equation in the electric background, and amplitudes of first-order Feynman diagrams describing the interaction with the photon field are calculated for massive Dirac particles in both valleys. Photon emission probabilities from a single electron and from a many-electron system at the charge neutrality point are derived, including the angular and frequency dependence, and several limiting cases are analyzed. The pattern of photon emission at the Dirac point in a strong field is determined by an interplay between the nonperturbative creation of electron–hole pairs and spontaneous emission, allowing for the possibility of observing the Schwinger effect in measurements of the radiation emitted by pristine graphene under DC voltage.     

Soliton pair creation at finite temperatures: Numerical study in (1 + 1) dimensions

Creation of soliton-antisoliton pairs at finite temperature is considered within a (1 + 1)-dimensional model of a real scalar field. It is argued that at certain temperatures, the soliton pair creation in quantum theory can be investigated by studying classical field evolution in real time. The classical field equations are solved numerically, and the pair creation rate and average number of solitons are evaluated. No peculiar suppression of the rate is observed. Some results on the sphaleron transitions in (1 + 1)-dimensional abelian Higgs model are also presented.     

Particle self-bunching in the Schwinger effect in spacetime-dependent electric fields

Nonperturbative electron-positron pair creation (the Schwinger effect) is studied based on the Dirac-Heisenberg-Wigner formalism in 1+1 dimensions. An ab initio calculation of the Schwinger effect in the presence of a simple space- and time-dependent electric field pulse is performed for the first time, allowing for the calculation of the time evolution of observable quantities such as the charge density, the particle number density or the total number of created particles. We predict a new self-bunching effect of charges in phase space due to the spatial and temporal structure of the pulse.     

Dressing up a Reissner naked singularity

Spontaneous pair creation in the field of a large Reissner singularity (a point-like charge e whose mass M is such that $\text{MG}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{< e}$) is here considered. Using as a guide the definition of the positive and negative energy states of a classical particle in this field, a particular basis of quantum states is chosen which contains resonance states — these are interpreted by invoking particle creation. Extremely energetic particles are shown to burst out to infinity whereas the antiparticles dress up and neutralize the singularity. This result is contrasted with the process of pair production by black holes and compared with the isotropization of the early universe by creation of matter.     

非线性啁啾频率对势阱产生正负电子对的增强

用计算量子场论方法研究了非线性啁啾频率对势阱中正负电子对产生的增强效应。研究了由静态势阱和动态势阱组成的组合势阱中产生的正负电子对的密度、产额和能谱等性质随着啁啾参数的变化,分析了组合势阱的频谱和瞬时束缚态。发现非线性啁啾效应对低频区域比较敏感,与固定频率情况相比可以使粒子数增加2～3倍。与组合势阱相比,非线性啁啾效应对单个振荡势阱更敏感。在低频下单个振荡的势阱中正负电子对产额可提高多个数量级。这是因为在低频下单个振荡的势阱中,主要通过量子隧穿过程产生的正负电子对数目非常低。非线性啁啾效应增加了高频场成分,提高了多光子过程和动力学辅助机制。由于高频抑制作用,所以非线性啁啾效应对高频区域粒子的增量不大,甚至会抑制正负电子对的产生。     

Fermion-boson coupling model (QCVM) applied to odd Zn isotopes

Low lying energy levels and transition probabilities of^63,65,67Zn are calculated in the Quasicluster-vibration model (QCVM). This model is an extension of the Clustervibration model (CVM) for three-particle-cluster vibration coupling. Instead of a three-particle cluster, now a one broken pair (number projected three quasiparticle) cluster is coupled to phonon states. It turns out that the sequence of isotopes may be described with one set of parameters, along the same line as previously used in the CVM. The resulting spectra and electromagnetic properties, for positive and negative parity states of odd Zn isotopes, compare with experimental data equally well as large shell-model calculations; this seems to justify the extension of the CVM to these nuclei with more than three particles or holes beyond a closed shell.     

Effects of classical random external field on the dynamics of entanglement in a four-qubit system

We investigate the dynamics of entanglement through negativity and witness operators in a system of four non-interacting qubits driven by a classical phase noisy laser characterized by a classical random external field (CREF). The qubits are initially prepared in the GHZ-type and W-type states and interact with the CREF in two different qubit-field configurations, namely, common environment and independent environments in which the cases of equal and different field phase probabilities are distinguished. We find that entanglement exhibits different decaying behavior, depending on the input states of the qubits, the qubit-field coupling configuration, and field phase probabilities. On the one hand, we demonstrate that the coupling of the qubits in a common environment is an alternative and more efficient strategy to completely shield the system from the detrimental impacts of the decoherence process induced by a CREF, independent of the input state and the field phase probabilities considered. Also, we show that GHZ-type states have strong dynamics under CREF as compared to W-type states. On the other hand, we demonstrate that in the model investigated the system robustness's can be greatly improved by increasing the number of qubits constituting the system.     

Holographic Schwinger effect

We study tunneling pair creation of W bosons by an external electric field on the Coulomb branch of N=4 supersymmetric Yang-Mills theory. We use AdS/CFT holography to find a generalization of Schwinger's formula for the pair production rate to the strong coupling, planar limit which includes the exchange of virtual massless particles to all orders. We find that the pair creation formula has an upper critical electric field beyond which the process is no longer exponentially suppressed. The value of the critical field is identical to that which occurs in the Born-Infeld action of probe D3-branes in the AdS(5)×S(5) background, where AdS(5) and S(5) are 5-dimensional anti-de Sitter space and the 5-sphere, respectively.     

Dynamical effects of switching a super-critical well potential on pair creation from a vacuum

The dynamical effects on electron-positron pair creation from a vacuum caused by the switching processes of a supercritical well potential are investigated in detail. The results show that only when the switching on and switching off time both increase will the final pair yield converge to the integer of embedded bound states nearly exponentially. But a single adiabatic switching on or switching off cannot lead to an integer pair yield. If the potential is turned on abruptly, associated with the discrete and embedded bound states, there is multi-frequency oscillation around the pair number's saturation. The slowly switching on can suppress the amplitude of this oscillation and reduce the final pair yield. The switching off can also reduce the final pair number in the same order of magnitude. The evolution of a single-pair number shows a robust long range correlation between particle and antiparticle. For an adiabatic switching case, the single-pair dominates the early pair creation, their upper limit value is equal to the integer, and these single-pairs will totally disentangle during the switching off.     

Dynamics of self-organized aggregation of resonant nanoparticles in a laser field

Self-organized aggregation of nanoparticles in external resonant laser field is considered using Brownian dynamics model. Formation probabilities are calculated for the pair of particles in dependence on laser wavelength and mutual orientation of particles. Times required for aggregation are calculated. Possibility of efficient aggregation using pulsed laser is deduced.     

Photo-production of scalar particles in the field of a circularly polarized laser beam

The photo-production of a pair of scalar particles in the presence of an intense, circularly polarized laser beam is investigated. Using the optical theorem within the framework of scalar quantum electrodynamics, explicit expressions are given for the pair production probability in terms of the imaginary part of the vacuum polarization tensor. Its leading asymptotic behavior is determined for various limits of interest. The influence of the absence of internal spin degrees of freedom is analyzed via a comparison with the corresponding probabilities for production of spin-1/2 particles; the lack of spin is shown to suppress the pair creation rate, as compared to the predictions from Dirac theory. Potential applications of our results for the search of minicharged particles are indicated.     

Jaynes—Cummings模型的非共振行为：原子能级占有几率和场的相干特性

采用相互作用图景,对相干态Jaynes-Cummings(JC)模型在失谐情况下导出了严格的解析解。用数值计算研究了原子能级占有几率与时间,失谐量和初始平均光子数的关系,发现原子能级占有几率对失谐量也表现出量子塌缩和再生现象;讨论了再生时间与再生信号之间的干涉现象。用数值计算研究了场的相干态的时间发展,发现JC模型一个有趣而又重要的新现象,即对于短时间范围,场态的发展表现出准可逆性,并详细讨论了这个现象。     

Geodesic deviation and particle creation in curved spacetimes

A quantum mechanical picture, relating accelerated geodesic deviation to creation of massive particles via quantum tunneling in curved background spacetimes, is presented. The effect is analogous to pair production by an electric field and leads naturally to production of massive particles in de Sitter and superluminal FRW spacetimes. The probability of particle production in de Sitter space per unit volume and time is computed in a leading semiclassical approximation and shown to coincide with the previously obtained expression.     

Quark pair creation in color electric fields and effects of magnetic fields

The time evolution of a system where a uniform and classical SU(3) color electric field and quantum fields of quarks interact with each other is studied focusing on non-perturbative pair creation and its back reaction. We characterize a color direction of an electric field in a gauge invariant way, and investigate its dependence. Momentum distributions of created quarks show plasma oscillation as well as quantum effects such as the Pauli blocking and interference. Pressure of the system is also calculated, and we show that pair creation moderates degree of anisotropy of pressure. Furthermore, enhancement of pair creation and induction of chiral charge under a color magnetic field which is parallel to an electric field are discussed.