Particle-antiparticle Pairs Research Articles

Holographic Schwinger effect in anisotropic media

According to gauge/gravity correspondence, we study the holographic Schwinger effect within an anisotropic background. Firstly, the separate length of the particle–antiparticle pairs is computed within the context of an anisotropic background which is parameterized by dynamical exponent ν\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ u $$\\end{document}. It is found that the maximum separate length x increases with the increase of dynamical exponent ν\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ u $$\\end{document}. By analyzing the potential energy, we find that the potential barrier increases with the dynamical exponent ν\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ u $$\\end{document} at a small separate distance. This observation implies that the Schwinger effect within an anisotropic background is comparatively weaker when contrasted with its manifestation in an isotropic background. Finally, we also find that the Schwinger effect in the transverse direction is weakened compared to the parallel direction in the anisotropic background, which is consistent with the top-down model.

From quantum foam to graviton condensation: The Zel'dovich route

Based on a previous ansatz by Zel'dovich for the gravitational energy of virtual particle-antiparticle pairs, supplemented with the holographic principle, we estimate the vacuum energy in a fairly reasonable agreement with the experimental values of the cosmological constant. We further highlight a connection between Wheeler's quantum foam and graviton condensation, as contemplated in the quantum N-portrait paradigm, and show that such connection also leads to a satisfactory prediction of the value of the cosmological constant. The above results suggest that the “unnaturally” small value of the cosmological constant may find a quite “natural” explanation once the nonlocal perspective of the large N-portrait gravitational condensation is endorsed.

Dynamic entanglement for continuous variables in an electric field background

Quantum entanglement is a typical nonclassical correlation. Here, we use this concept to analyze quantum entanglement for continuous variables generated by the Schwinger pair production for constant and pulsed electric fields. An initial two-mode entangled state evolves into a three-mode entangled state through a Gaussian channel of the Schwinger effect, which encodes the information about the Schwinger effect. By detecting the entanglement of the output three-mode state, we obtain the optimal parameters for easier to generate particle–antiparticle pairs. We find that the generated 1 → 2 entanglement is more sensitive to the parameters than the generated 1 → 1 entanglement. Therefore, we should choose the generated 1 → 2 entanglement to extract information. We argue that extracting the optimal parameters from quantum entanglement may guide future experiments.

Magnonic Klein and acausal tunneling enabled by breaking the anti parity-time symmetry in antiferromagnets

Klein tunneling associated with particle-antiparticle pair productions across a potential barrier is a key prediction of quantum-field theory for relativistic particles. Yet, a direct experimental realization is hampered by the particles large rest mass resulting in high potential barrier. Here, for non-Hermitian antiferromagnets, at the verge of the anti-parity-time symmetry transition, chiral magnons are demonstrated to offer a bosonic platform to access Klein tunneling at meV energies in experimentally feasible settings. Our analytical and numerical simulations evidence that magnetic damping renders a low energy mechanism for the breakdown of the magnonic vacuum and for creating particle-antiparticle pairs in strong magnetic fields. Adopting Feynman’s picture for antiparticles, the tunneling time of an incident magnon wave packet across a supercritical barrier is found to be negative. The uncovered aspects point to the potential of chiral magnons for addressing fundamental physics in a conceptually simple setup with the potential for use in chirality-dependent magnonic computing.

Massive particle pair production and oscillation in Friedman Universe: reheating energy and entropy, and cold dark matter

Suppose that the early Universe starts with a cosmological Lambda -term (dark energy) originating from quantum spacetime at the Planck scale. Dark energy drives inflation and reheating by reducing its value for massive particle–antiparticle pairs production and oscillation, resulting in a holographic and massive pair plasma state. The back-and-forth reaction of dark energy and massive pairs slows inflation to its end and starts reheating by rapidly producing stable and unstable pairs. We introduce the Boltzmann-type rate equation describing the back-and-forth reaction. It forms a close set with Friedman equations and reheating equations for unstable pairs decay to relativistic particles. The numerical solutions show preheating, massive pairs dominated and genuine reheating episodes. We obtain the reheating temperature and entropy in terms of the tensor-to-scalar ratio 0< r < 0.047 consistently with observations. Stable massive pairs represent cold dark matter particles and weakly interact with dark energy. The resultant cold dark matter abundance Omega _csim 10^{-1} is about a constant in time.

Electromagnetic properties of the quantum vacuum calculated from its structure

Maxwell’s equations and quantum electrodynamics are valid for any value of the permittivity ϵ0 of the vacuum; therefore, something additional is required to establish the value of ϵ0. A fundamental postulate of physics is that the properties of a physical system are determined by its structure. Since ϵ0 is an electromagnetic property of the vacuum, it should be possible to calculate ϵ0 using Maxwell’s equations and quantum electrodynamics to describe the interaction of photons with the quantum vacuum. The feature of the quantum vacuum that allows for such interactions is the presence of vacuum fluctuations that appear as particle-antiparticle pairs. To minimize the violation of energy conservation and conserve angular momentum, the pair appears with zero center-of-mass momentum in the most tightly bound state that has zero angular momentum. Because vacuum fluctuations each appear as a bound state, the permittivity of the vacuum can be calculated somewhat similarly to the way that the permittivity of a dielectric is calculated, yielding ϵ0 ≃ (6μ o/π)(8e 2/ħ)2 = 9.10 × 10−12C/(Vm), which is 2.8% larger than the experimental value. Formulas for the speed of light in the vacuum and the fine-structure constant follow immediately from the formula for ϵ0.

Mesoscopic Klein-Schwinger effect in graphene

Strong electric field annihilation by particle–antiparticle pair creation, also known as the Schwinger effect, is a non-perturbative prediction of quantum electrodynamics. Its experimental demonstration remains elusive, as threshold electric fields are extremely strong and beyond current reach. Here, we propose a mesoscopic variant of the Schwinger effect in graphene, which hosts Dirac fermions with an approximate electron–hole symmetry. Using transport measurements, we report on universal one-dimensional Schwinger conductance at the pinchoff of ballistic graphene transistors. Strong pinchoff electric fields are concentrated within approximately 1 μm of the transistor’s drain and induce Schwinger electron–hole pair creation at saturation. This effect precedes a collective instability towards an ohmic Zener regime, which is rejected at twice the pinchoff voltage in long devices. These observations advance our understanding of current saturation limits in ballistic graphene and provide a direction for further quantum electrodynamic experiments in the laboratory.

Nonthermal radiation of evaporating black holes

Black hole (BH) evaporation is caused by creation of entangled particle-antiparticle pairs near the event horizon, with one carrying positive energy to infinity and the other carrying negative energy into the BH. Since under the event horizon, particles always move toward the BH center, they can only be absorbed but not emitted at the center. This breaks absorption-emission symmetry and, as a result, annihilation of the particle at the BH center is described by a non-Hermitian Hamiltonian. We show that due to entanglement between photons moving inside and outside the event horizon, nonunitary absorption of the negative energy photons near the BH center, alters the outgoing radiation. As a result, radiation of the evaporating BH is not thermal; it carries information about BH interior, and entropy is preserved during evaporation.

Massive particle pair production and oscillation in Friedman Universe: its effect on inflation

We study the classical Friedman equations for the time-varying cosmological term tilde{Lambda } and Hubble function H, together with quantised field equations for the production of massive Mgg H particles, namely, the tilde{Lambda }CDM scenario of dark energy and matter interactions. Classical slow components {mathcal O}(H^{-1}) are separated from quantum fast components {mathcal O}(M^{-1}). The former obeys the Friedman equations, and the latter obeys a set of nonlinear differential equations. Numerically solving equations for quantum fast components, we find the production and oscillation of massive particle-antiparticle pairs in microscopic time scale {mathcal O}(M^{-1}). Their density and pressure averages over microscopic time do not vanish. It implies the formation of a massive pair plasma state in macroscopic time scale {mathcal O}(H^{-1}), whose effective density and pressure contribute to the Friedman equations. Considering the inflation driven by the time-varying cosmological term and slowed down by the massive pair plasma state, we obtain the relation of spectral index and tensor-to-scalar ratio in agreement with recent observations. We discuss the singularity-free pre-inflation, the CMB large-scale anomaly, and dark-matter density perturbations imprinting on power spectra.

Estimating today's cosmological constant via the Zel'dovich-holographic connection

This letter proposes an approach to the vacuum energy and the cosmological constant (CC) paradox based on the Zel’dovich's ansatz, which states that the observable contribution to the vacuum energy density is given by the gravitational energy of virtual particle-antiparticle pairs, continually generated and annihilated in the vacuum state. The novelty of this work is the use of an ultraviolet cut-off length based on the holographic principle, which is shown to yield current values of the CC in semi-quantitative agreement with experimental observations.

Space-time-resolved quantum field approach to Klein-tunneling dynamics across a finite barrier

Klein tunneling takes place when a particle scatters on a supercritical barrier that is creating particle antiparticle pairs. The authors, using a space-time resolved relativistic quantum field theory approach, show that the transmitted particle does not tunnel through the barrier but is instead produced by modulations in the pair creation rate.

Discovery prospects for long-lived multiply charged particles at the LHC

In this work, we aim to provide a comprehensive and largely model independent investigation on prospects to detect long-lived multiply charged particles at the LHC. We consider particles with spin 0 and frac{1}{2}, with electric charges in range 1 le |Q/e| le 8, which are singlet or triplet under SU(3)_C. Such particles might be produced as particle-antiparticle pairs and propagate through detectors, or form a positronium (quarkonium)-like bound state. We consider both possibilities and estimate lower mass bounds on new particles, that can be provided by ATLAS, CMS and MoEDAL experiments at the end of Run 3 and HL-LHC data taking periods. We find out that the sensitivities of ATLAS and CMS are generally stronger than those of MoEDAL at Run 3, while they may be competitive at HL-LHC for 3 lesssim |Q/e| lesssim 7 for all types of long-lived particles we consider.

Brownian-Huygens Propagation: Modeling Wave Functions with Discrete Particle-Antiparticle Random Walks

We present a simple method of discretely modeling solutions of the classical wave and Klein-Gordon equations using variations of random walks on a graph. Consider a collection of particles executing random walks on an undirected bipartite graph embedded in mathbb {R}^{D} at discrete times mathbb {Z}, and assume those walks are “heat-like”, in the sense that a (conserved) density of particles obeys the heat equation in the continuum limit. If the particles possess a binary degree of freedom (so that they may be said to be either particles or “antiparticles”, i.e., “positive” or “negative), then there exist closely related branching random walks on the same graph that are “wave-like”, in the sense that their (also conserved) net density obeys the D-dimensional classical wave equation. Such wave-like paths can be generated even on random graphs. The transformation by which the heat-like random walks become wave-like branching random walks is as follows: at every time step, any “incoming” particle arriving at any node X of the graph along some edge eX creates a particle-antiparticle pair at that node, with the stipulation that the newly created particle with the opposite sign of the incoming particle must initially step (in “Huygens” back-propagation fashion) along eX in the reverse direction, while the other two take a step (in “Brownian” fashion) along any edge of X (including possibly eX) with equal likelihood, and chosen independently. An additional degree of freedom (resulting in “bra” and “ket” particles) leads to quasi-probability densities proportional to the square of the wave functions.

Lorentz invariance and the spinor-helicity formalism yield the U(1) and SU(3) fermion symmetry

In this paper we use the so-called spinor-helicity formalism to represent three-vectors in terms of the Pauli matrices and derive a generalized relativistic wave equation for a massive fermion of spin one-half. We thus extend the Dirac equation by making use of the Pauli-Lubański operator that includes isospin explicitly. As a consequence, we get new degrees of freedom related to isospin helicity, in addition to the two standard ones of the Dirac equation that are associated with the kinetic spin-helicity doublet and the particle-antiparticle pair. Formally, isospin helicity has 2(2s+1) degrees of freedom for an arbitrary general isospin s and has the eigenvalues s and -(s+1), and thus it reveals a kind of hidden symmetry in any isospin field. The resulting four degrees of freedom for isospin 1/2 are interpreted as being associated with two independent subspaces of dimension 1 related to the U(1) and 3 related to SU(3) symmetry, i.e. to the leptons and quarks.

Skyrmion–antiskyrmion pair creation and annihilation in a cubic chiral magnet

A fundamental property of particles and antiparticles (such as electrons and positrons, respectively) is their ability to annihilate one another. A similar behaviour is predicted for magnetic solitons1—localized spin textures that can be distinguished by their topological index Q. Theoretically, magnetic topological solitons with opposite values of Q, such as skyrmions2 and their antiparticles (namely, antiskyrmions), are expected to be able to continuously merge and annihilate3. However, experimental verification of such particle–antiparticle pair production and annihilation processes has been lacking. Here we report the creation and annihilation of skyrmion–antiskyrmion pairs in an exceptionally thin film of the cubic chiral magnet of B20-type FeGe observed using transmission electron microscopy. Our observations are highly reproducible and are fully consistent with micromagnetic simulations. Our findings provide a new platform for the fundamental studies of particles and antiparticles based on magnetic solids and open new perspectives for practical applications of thin films of isotropic chiral magnets.

Electric field decay without pair production: lattice, bosonization and novel worldline instantons

Electric fields can spontaneously decay via the Schwinger effect, the nucleation of a charged particle-anti particle pair separated by a critical distance d. What happens if the available distance is smaller than d? Previous work on this question has produced contradictory results. Here, we study the quantum evolution of electric fields when the field points in a compact direction with circumference L < d using the massive Schwinger model, quantum electrodynamics in one space dimension with massive charged fermions. We uncover a new and previously unknown set of instantons that result in novel physics that disagrees with all previous estimates. In parameter regimes where the field value can be well-defined in the quantum theory, generic initial fields E are in fact stable and do not decay, while initial values that are quantized in half-integer units of the charge E = (k/2)g with k ∈ ℤ oscillate in time from +(k/2)g to −(k/2)g, with exponentially small probability of ever taking any other value. We verify our results with four distinct techniques: numerically by measuring the decay directly in Lorentzian time on the lattice, numerically using the spectrum of the Hamiltonian, numerically and semi-analytically using the bosonized description of the Schwinger model, and analytically via our instanton estimate.

Hide and seek with the third family hypercharge model\u2019s Z^prime at the large hadron collider

The Third Family Hypercharge Model predicts a Z^prime gauge boson with flavour dependent couplings which has been used to explain anomalies in meson decay processes which involve the brightarrow smu ^+mu ^- transition. The model predicts that a TeV-scale Z^prime should decay to particle-antiparticle pairs of muons, taus, top quarks and bottom quarks with appreciable branching ratios. We reinterpret various ATLAS and CMS search limits for Z^prime production followed by such decays at the LHC over a parameter space of the model that results from a successful combined fit to the brightarrow s l^+ l^- data and precision electroweak observables. Current exclusions in parameter space and expected sensitivities of the various different channels in the high-luminosity run are compared. We find that the high-luminosity run of the LHC will significantly increase the sensitivity to the model beyond the existing empirical limits, which we find to be surprisingly weak.

The Speed of Light Predicts the Number of Lepton Families

Vacuum fluctuations of charged particles appear in the vacuum as particle-antiparticle pairs so that quantum numbers such as charge, baryon number, and lepton number are conserved. To minimize the violation of conservation of energy and conserve angular momentum, the pair appears in the most tightly bound state that has zero angular momentum. The permittivity ϵ0 of the vacuum results primarily from bound, charged lepton-charged antilepton vacuum fluctuations that are polarized by photons traveling in the vacuum. The formula for ϵ0 depends on the number NL of lepton families but is independent of the charged lepton masses. The formula for the speed c of light in the vacuum is obtained from c=1/μ0ϵ0, where μ0 is the permeability of the vacuum. The formula for c is shown to depend on the number NL of lepton families. The calculated value of c agrees with the defined value when NL=2.92.

Backreaction of Schwinger pair creation in massive QED2

Particle-antiparticle pairs can be produced by background electric fields via the Schwinger mechanism provided they are unconfined. If, as in QED in (3+1)-d these particles are massive, the particle production rate is exponentially suppressed below a threshold field strength. Above this threshold, the energy for pair creation must come from the electric field itself which ought to eventually relax to the threshold strength. Calculating this relaxation in a self-consistent manner, however, is difficult. Chu and Vachaspati addressed this problem in the context of capacitor discharge in massless QED2 [1] by utilizing bosonization in two-dimensions. When the bare fermions are massless, the dual bosonized theory is free and capacitor discharge can be analyzed exactly [1], however, special care is required in its interpretation given that the theory exhibits confinement. In this paper we reinterpret the findings of [1], where the capacitors Schwinger-discharge via electrically neutral dipolar meson-production, and generalize this to the case where the fermions have bare masses. Crucially, we note that when the initial charge of the capacitor is large compared to the charge of the fermions, Q » e, the classical equation of motion for the bosonized model accurately characterizes the dynamics of discharge. For massless QED2, we find that the discharge is suppressed below a critical plate separation that is commensurate with the length scale associated with the meson dipole moment. For massive QED2, we find in addition, a mass threshold familiar from (3+1)-d, and show the electric field relaxes to a final steady state with a magnitude proportional to the initial charge. We discuss the wider implications of our findings and identify challenges in extending this treatment to higher dimensions.

Particle-antiparticle pair production from vacuum and the imaginary proper time method

Using the imaginary proper time method, based on the Fock method of solving the relativistic wave equations, the process of fermionic and scalar pairs production from a vacuum by a constant uniform electric field is considered. The relative (conditional) probability of the one pair production, which does not depend on the possible production of other pairs, was obtained with exponential accuracy, and the absolute probability of pair production, which takes into account the particle statistics, was obtained with pre-exponential accuracy.