Vacuum Pair Creation Research Articles

Dunkl algebra and vacuum pair creation: Exact analytical results via Bogoliubov method

This paper examines the generation of scalar particle pairs resulting from the application of an external electric field's Coulomb potential in both three- and two-dimensional scenarios, employing Dunkl's formalism. In doing this, we present two distinct sets of exact solutions to the Dunkl-Klein-Gordon equation. Subsequently, we employ the canonical approach based on the Bogoliubov transformation to link the “in” and “out” states in order to compute both the probability of pair creation and the density of particle creation. It is shown that the conditions necessary for the creation of pairs of spinless particles depend on several factors: nucleus charge Z, quantum numbers, and Dunkl parameter. It is also shown that the Dunkl formalism enhances particle pair production.

A hybrid nodal-staggered pseudo-spectral electromagnetic particle-in-cell method with finite-order centering

Electromagnetic particle-in-cell (PIC) codes are widely used to perform computer simulations of a variety of physical systems, including fusion plasmas, astrophysical plasmas, plasma wakefield particle accelerators, and secondary photon sources driven by ultra-intense lasers. In a PIC code, Maxwell's equations are solved on a grid with a numerical method of choice. This article focuses on pseudo-spectral analytical time-domain (PSATD) algorithms and presents a novel hybrid PSATD PIC scheme that combines the respective advantages of standard nodal and staggered methods. The novelty of the hybrid scheme consists in using finite-order centering of grid quantities between nodal and staggered grids, in order to combine the solution of Maxwell's equations on a staggered grid with the deposition of charges and currents and the gathering of electromagnetic forces on a nodal grid. The correctness and performance of the novel hybrid scheme are assessed by means of numerical tests that employ different classes of PSATD equations in a variety of physical scenarios, ranging from the modeling of electron-positron pair creation in vacuum to the simulation of laser-driven and particle beam-driven plasma wakefield acceleration. It is shown that the novel hybrid scheme offers significant numerical and computational advantages, compared to purely nodal or staggered methods, for all the test cases presented.

Temporal Klein Model for Particle-Pair Creation

This work considers the creation of electron-positron pairs from intense electric fields in vacuum, for arbitrary temporal field variations. These processes can be useful to study quantum vacuum effects with ultra-intense lasers. We use the quantized Dirac field to explore the temporal Klein model. This model is based on a vector potential discontinuity in time, in contrast with the traditional model based on a scalar potential discontinuity in space. We also extend the model by introducing a finite time-scale for potential variations. This allows us to study the transition from a singular electric field spike, with infinitesimal duration, to the opposite case of a static field where the Schwinger formula would apply. The present results are intrinsically non-perturbative. Explicit expressions for pair-creation as a function of the potential time-scales are derived. This work explores the spacetime symmetry associated with pair creation in vacuum: the space symmetry breaking of the old Klein paradox model, in contrast with the time symmetry breaking of the temporal Klein model.

Multi-photon enhancement of the Schwinger pair production mechanism under strong FEL radiation

In this work we study the production of electron-positron pairs from vacuum in presence of a field resulting from the collision of two counter-propagating FEL beams that undergo Gaussian amplitude fluctuations. Our work aims to the extension of previous works based on the standing wave hypothesis, by including the inherent stochastic amplitude fluctuations of the individual FEL beams. As shown, depending on the order of the process, a large non-linear enhancement in the number of created pairs can be expected over a big intensity window in the multi-photon regime. Vacuum pair creation in view of future plans on the production of ultra-strong and high energy radiation in FEL facilities is also discussed.

Chirp effects on pair production in oscillating electric fields with spatial inhomogeneity

Chirp effects on the vacuum pair creation are studied with space and time dependent electric field models. For rapidly oscillating electric fields, the total particle number enhancement only occurs for larger chirp values and the very large chirp may render the effect from the finite spatial size trivial. For slowly oscillating electric fields, the chirp and carrier phase parameters have crucial effects on the particle momentum distribution. The quasihomogeneous results are analyzed using local density approximation where the consequence of the field strength dependence of the homogeneous results is noticed.

Nonperturbative Kinetic Description of Electron-Hole Excitations in Graphene in a Time Dependent Electric Field of Arbitrary Polarization

On the basis of the well-known kinetic description of e − e + vacuum pair creation in strong electromagnetic fields in D = 3 + 1 QED we construct a nonperturbative kinetic approach to electron-hole excitations in graphene under the action of strong, time-dependent electric fields. We start from the simplest model of low-energy excitations around the Dirac points in the Brillouin zone. The corresponding kinetic equations are analyzed by nonperturbative analytical and numerical methods that allow to avoid difficulties characteristic for the perturbation theory. We consider different models for external fields acting in both, one and two dimensions. In the latter case we discuss the nonlinear interaction of the orthogonal currents in graphene which plays the role of an active nonlinear medium. In particular, this allows to govern the current in one direction by means of the electric field acting in the orthogonal direction. Investigating the polarization current we detected the existence of high frequency damped oscillations in a constant external electric field. When the electric field is abruptly turned off residual inertial oscillations of the polarization current are obtained. Further nonlinear effects are discussed.

On the problems of relativistic laboratory astrophysics and fundamental physics with super powerful lasers

The ways toward modeling of astrophysical processes and extreme field regimes with super-power lasers are discussed. The main attention is paid to the problem of limited similarity in using the dimensionless parameters characterizing the processes in the laser and astrophysical plasmas. As the most typical examples, we address the magnetic reconnection and collisionless shock waves relevant to the problem of ultrarelativistic particle acceleration. In the extreme field limits we consider the regimes of dominant radiation reaction, changing the electromagnetic wave-matter interaction. In these regimes it, in particular, results in a new powerful source of ultra high-brightness gamma-rays and will make possible electron-positron pair creation in vacuum in a multiphoton processes. This will allow modeling under terrestrial laboratory conditions the processes in astrophysical objects and paves the way to experimental verifications using ultra intense lasers as they are currently developed within the ELI project.

Smoothed solutions in the kinetic theory of e+e- vacuum pair creation in strong laser fields. Linear polarization

In this paper, the dynamical Schwinger effect of vacuum creation of electron–positron pairs driven by an intense laser pulse is studied on the basis of correct quantum kinetic theory. In the general case, the numerical solutions of corresponding system of kinetic equations exhibit complex time dependence which makes the analysis of the physical processes complicated. In particular, the question of secondary effects, such as creation of annihilation photons from the focus spot of the colliding laser beams, remains an important open problem. In our previous work [S. A. Smolyansky, M. Bonitz and A. V. Prozorkevich, Contrib. Plasma Phys.53 (2013) 788], we presented a perturbation theory which is able to capture the dominant time dependence of the produced electron–positron pair distribution during the pulse (quasiparticle excitations). In the present work, we develop appreciably this approximation scheme. We demonstrate effectiveness of the proposed method for solution of such kind nonstationary problems in the simplest models of the laser field. However, this approach opens perspective for search of the relevant approximate solutions in kinetic theory of the e+e- quasiparticle plasma for the more realistic field models (arbitrary polarization, space inhomogeneous, etc).

Laser Driven Electron‐Positron Pair Creation–Kinetic Theory Versus Analytical Approximations

AbstractThe dynamical Schwinger effect of vacuum pair creation driven by an intense external laser pulse is studied on the basis of quantum kinetic theory. The numerical solutions of these kinetic equations exhibit a complex time dependence which makes an analysis of the physical processes difficult. In particular, the question of secondary effects, such as creation of secondary annihilation photons from the focus spot of the colliding laser beams, remains an important open problem. In the present work we, therefore, develop a perturbation theory which is able to capture the dominant time dependence of the produced electron‐positron pair density. The theory shows excellent agreement with the exact kinetic results during the laser pulse, but fails to reproduce the residual pair density remaining in the system after termination of the pulse. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

On the design of experiments for the study of extreme field limits in the interaction of laser with ultrarelativistic electron beam

We propose the experiments on the collision of laser light and high intensity electromagnetic pulses generated by relativistic flying mirrors, with electron bunches produced by a conventional accelerator and with laser wake field accelerated electrons for studying extreme field limits in the nonlinear interaction of electromagnetic waves. The regimes of dominant radiation reaction, which completely changes the electromagnetic wave-matter interaction, will be revealed in the laser plasma experiments. This will result in a new powerful source of ultra short high brightness gamma-ray pulses. A possibility of the demonstration of the electron-positron pair creation in vacuum in a multi-photon processes can be realized. This will allow modeling under terrestrial laboratory conditions neutron star magnetospheres, cosmological gamma ray bursts and the Leptonic Era of the Universe.

Feynman disentangling of noncommuting operators and group representation theory

Feynman's method for disentangling noncommuting operators is discussed and applied to nonstationary problems in quantum mechanics, including the excitation ofa harmonic oscillator by an external force and/or by time-varying frequency; spin rotation in a time-varying magnetic field; the disentangling of an atom (ion) Hamiltonian in a laser field; a model with the hidden symmetry group of the hydrogen atom; and the theory of coherent states. The Feynman operator calculus combined with simple group-theoretical considerations allows disentangling the Hamiltonian and obtaining exact transition probabilities between the initial and final states of aquantum oscillator in analytic form without cumbersome calculations. The case of a D-dimensional oscillator is briefly discussed, in particular, in application to the problem of vacuum pair creation in an intense electric field.

Observable manifestation of an electron-positron plasma created by the field of an optical laser

Electron-positron vacuum pair creation in the quasi-periodic electric field of a standing wave is investigated for field strengths and frequencies corresponding to modern optical lasers using a quantum kinetic equation with a non-markovian source term. For a field E ∼ 5 · 1011 V/cm, the instantaneous quasiparticle electron-positron plasma is created which maximum density of order 1020cm−3. The mean value of the pair density per period <n> exceeds by many orders of magnitude the residual density nr which is taken over an integer number of field periods. The value <n> is proportional to the squared field intensity and does not depend on the frequency at ν ≪ m. Under conditions of presently available optical lasers with intensities exceeding I ∼ < 1020W/cm2, the mean number of created pairs in the volume of a wavelength cubed is about 107 which corresponds to 5 - 10 two-photon annihilation events per one laser pulse. The generated γ-quanta are suggested to be an observable signal of e+ e− pair vacuum creation in experiments with counter-propagating optical laser beams.

Formation of cyclotron-annihilation lines in magnetized vacuum near neutron stars

We study the formation of the absorption features, called the cyclotron–annihilation lines, in the γ-spectra of the neutron stars (pulsars), owing to the fundamental quantum-electrodynamic effect of the one–photon pair creation in magnetized vacuum. As a result, we substantiate a new method for the determination of the neutron star magnetic fields B based on measuring the interval between the main annihilation and the first cyclotron–annihilation absorption lines. It is found that these lines may be easily resolved, and, consequently, the method is surely applicable if the following conditions are satisfied. (i) A γ-source has to be compact enough and located near a star, but not close to its magnetic poles. For instance, it may be a disc in the plane of a star magnetic equator with latitudinal angular width less than and radial extent up to 25 per cent of the star radius. (ii) The source is to produce detectable γ-radiation at large angles ≳60° to the local magnetic field. Being situated in a closed field line region and having a broad radiation pattern, such a source is not what is usually considered in the context of the polar cap and outer gap models of the pulsar γ-emission dealing with open field lines only. (iii) Magnetic field strength must lie in a certain narrow interval with the centre at ∼(3–4) × 1012 G. Its width depends on the star orientation and disc radial extend and in the most favourable case is about 20–30 per cent of its lower boundary. Finally, the influence of the star rotation on this method employment is considered and new possibilities arising from forthcoming polarization observations are briefly discussed.

Kinetic description of vacuum creation of massive vector bosons

In the simple model of massive vector field in a flat spacetime, we derive the kinetic equation of non-Markovian type describing the vacuum pair creation under action of external fields of different nature. We use for this aim the nonperturbative methods of kinetic theory in combination with a new element when the transition of the instantaneous quasiparticle representation is realized within the oscillator (holomorphic) representation. We study in detail the process of vacuum creation of vector bosons generated by a time-dependent boson mass in accordance with the framework of a conformal-invariant scalar-tensor gravitational theory and its cosmological application. It is indicated that the choice of the equation of state allows one to obtain a number density of vector bosons that is sufficient to explain the observed number density of photons in the cosmic microwave background radiation.

Anyons from nonsolvable finite groups are sufficient for universal quantum computation

We present a constructive proof that anyonic magnetic charges with fluxes in a non-solvable finite group can perform universal quantum computations. The gates are built out of the elementary operations of braiding, fusion, and vacuum pair creation, supplemented by a reservoir of ancillas of known flux. Procedures for building the ancilla reservoir and for correcting leakage are also described. Finally, a universal qudit gate-set, which is ideally suited for anyons, is presented. The gate-set consists of classical computation supplemented by measurements of the X operator.

The kinetic approach to parton production under the conditions of ultrarelativistic heavy ion collisions

Dynamics of partons created through vacuum tunneling in time-dependent spatially homogenous field is studied for typical conditions of ultra-relativistic heavy-ion collisions. In the relaxation-time approximation, a thermalization scenario for such quasi-particle plasma is considered. A local equilibrium state of the system is described in the frame-work of two-component thermodynamics of particles and anti-particles. In the evolution towards an equilibrium are involved three parallel mechanisms: (i) spontaneous vacuum pair creation, (ii) back-reaction of the produced particles to the background field, (iii) collisions between the charged particles. We solve numerically a self-consistent system of the Vlasov-like kinetic equation with a source and collision term and the renormalized Maxwell equation. A possibility of introducing, the temperature conception under the condition of strong vacuum polarization is discussed.

Production of Diracparticles in vacuum by external fields in d + 1 (d = 3,2,1)dimensions

We calculate the probability of pair creation in vacuum in d + 1dimensions (with d = 3,2,1), by an alternating electromagnetic field,in three cases. First, we consider an electromagnetic field composed of analternating electric field and of a constant uniform magnetic field. Next,we consider the situation when both the electric and magnetic fields arepurely alternating. Finally, we complete this analysis with the case ofproduction of Dirac particles in vacuum by a constant uniformelectromagnetic field and a plane wave.

High‐Energy Gamma‐Ray Emission from Galactic Kerr‐Newman Black Holes. I. The Central Engine

A model of the central engine of the unidentified high-latitude galactic hard γ-ray (EGRET) sources based on black hole electrodynamics is presented. The γ-ray emission is produced in a bipolar outflow from a charged, rotating black hole (a Kerr-Newman black hole) in a low-density region of the Galaxy, the details of which are provided in a companion paper. The model proposed in this article and its companion is a synthesis of pair creation scenarios for pulsars, the theory of black hole magnetospheres and synchrotron self-Compton large-scale jets. This article describes the physics of the putative central engine. Kerr-Newman black holes are plausible endpoints of the catastrophic gravitational collapse of the most massive magnetized rotating stars. In the following, the ability of a Kerr-Newman black hole to drive a magnetically dominated plasma wind in the charge-starved limit is explored for the first time. Although there are important analogies to magnetohydrodynamic (MHD) wind theory of Kerr (uncharged rotating) black holes, there are also enormous distinctions. However, previous experience with the MHD Kerr case is exploited to render this more complicated problem tractable. The most important parameter for quantifying the wind energy is the magnetic field line angular velocity, ΩF (and unfortunately the most difficult to calculate). The determination of ΩF is tied directly to the process by which a pair plasma is created on large-scale magnetic field lines through high-energy quantum electrodynamic processes typical of pulsar magnetospheres. It is argued in principle how ΩF is determined by the plasma injection mechanism. Furthermore, the most significant result of this effort is the calculation of ΩF for a model that is determined by a plausible set of astronomical parameters. It is essential to realize a distinction from some charge-starved pulsar models: the energy source for the wind is quantified by the field line rotation rate (the cross-field potential), ultimately powered by the rotation of the hole through dissipative gravitomagnetic processes and not the volage drop across the vacuum pair creation gap.

Validity of the infinite-momentum frame canonical formalism for simple loop diagrams

Field theory in the infinite-momentum frame has a number of simplifying features: absence of vacuum-pair creation and a nonrelativistic analogy connected with the existence of a two-dimensional Galilean subgroup of the Poincar6 group. High-energy approximations for electromagnetic processes and, in this formalism, the parton model can be derived in a very elegant and transparen~ way. Two methods, I and II can be used to obtain a per turbat ive expansion which exhibits this underlying Galilean structure. In method I one starts by writing the noncovariant perturbative expansion in a frame where the particles involved in the physical process under consideration have fi ire energies; then, to this frame one applies a Lorentz boost with a velocity v almost equal to c and retains the dominant term in the limit v--> c. I t is the original approach of W E I N ~ G (~), and has been used by DRELL et al. to discuss high-energy electron scattering (2). The second approach is much more elegant, and makes systematic use of a change of variables in space t ime (3,~). A space-time event is described by the following new variables: