Particle-antiparticle Pairs Research Articles

Schwinger effect and backreaction in de Sitter spacetime

We consider the particle-antiparticle pairs produced by both a strong electric field and de Sitter curvature. We investigate in 1 + 1 D the backreaction of the pairs on the electromagnetic field. To do so we describe the canonical quantization of an electromagnetic field in de Sitter space and add in the Einstein-Maxwell equation the fermionic current induced by the pairs. After solving this equation, we find that the electric field gets either damped or unaffected depending on the value of the pair mass and the gauge coupling. No enhancement of the electromagnetic field to support a magnetogenesis scenario is found. The physical picture is that the Schwinger pairs locally created screen the production and amplification of the electromagnetic field. However, if one considers light bosons created by the Schwinger mechanism, we report a solution to the Einstein-Maxwell equation with an enhancement of the electromagnetic field. This solution could be a new path to primordial magnetogenesis.

Low-dimensional approach to pair production in an oscillating electric field: Application to bandgap graphene layers

The production of particle-antiparticle pairs from the quantum field theoretic ground state in the presence of an external electric field is studied. Starting with the quantum kinetic Boltzmann-Vlasov equation in four-dimensional spacetime, we obtain the corresponding equations in lower dimensionalities by way of spatial compactification. Our outcomes in $2+1$-dimensions are applied to bandgap graphene layers, where the charge carriers have the particular property of behaving like light massive Dirac fermions. We calculate the single-particle distribution function for the case of an electric field oscillating in time and show that the creation of particle-hole pairs in this condensed matter system closely resembles electron-positron pair production by the Schwinger effect.

The Inward Dispersion of the Neutron Scattering Experiments in HTSC Cuprates

The theory of the high temperature superconducting cuprates, which is based on the condensation of holes into strings in checker-board geometry, was successful to explain the elastically scattered Neutrons by spin waves. Here it is extended to analyze the inward dispersion curve of its inelastic counterpart, up to the resonance energy- . This extension is done by applying the perturbation theory of the linear response to the condensed strings. The approximated susceptibility is derived by means of the ring diagram. The dispersion relation is obtained from the dispersion of the poles of the susceptibility integral. It is found that the particle anti-particle pair that yields the susceptibility is the time reversal pair where the particle momentum is in phase A, and the anti-particle momentum is in phase B. The dispersion is found to be in agreement with experiment, subject to some suggested corrections. The weak intensity by the resonance energy, as well as the dispersion, is speculated to be modified due to interference with spin waves that are caused by direct spin flip, as in the mother undoped materials.

Hydrodynamics of the Physical Vacuum: II. Vorticity Dynamics

Physical vacuum is a special superfluid medium populated by enormous amount of virtual particle-antiparticle pairs. Its motion is described by the modified Navier-Stokes equation: (a)~the pressure gradient divided by the mass density is replaced by the gradient from the quantum potential; (b)~time-averaged the viscosity vanishes, but its variance is not zero. Vortex structures arising in this medium show infinitely long lifetime owing to zero average viscosity. The nonzero variance is conditioned by exchanging the vortex energy with zero-point vacuum fluctuations. The vortex has a non-zero core where the orbital speed vanishes. The speed reaches a maximal value on the core wall and further it decreases monotonically. The vortex trembles around some average value and possesses by infinite life time. The vortex ball resulting from topological transformation of the vortex ring is considered as a model of a particle with spin. Anomalous magnetic moment of electron is computed.

Hydrodynamics of the Physical Vacuum: I. Scalar Quantum Sector

Physical vacuum is a special superfluid medium. Its motion is described by the Navier-Stokes equation having two slightly modified terms that relate to internal forces. They are the pressure gradient and the dissipation force because of viscosity. The modifications are as follows: (a) the pressure gradient contains an added term describing the pressure multiplied by the entropy gradient; (b) time-averaged viscosity is zero, but its variance is not zero. Owing to these modifications, the Navier-Stokes equation can be reduced to the Schrodinger equation describing behavior of a particle into the vacuum, which looks like a superfluid medium populated by enormous amount of virtual particle-antiparticle pairs.

The particle production at the event horizon of a black hole as gravitational Fowler-Nordheim emission in uniformly accelerated frame, in the non-relativistic scenario

In the conventional scenario, the Hawking radiation is believed to be a tunneling process at the event horizon of the black hole. In the quantum field theoretic approach the Schwinger’s mechanism is generally used to give an explanation of this tunneling process. It is the decay of quantum vacuum into particle anti-particle pairs near the black hole surface. However, in a reference frame undergoing a uniform accelerated motion in an otherwise flat Minkowski space-time geometry, in the non-relativistic approximation, the particle production near the event horizon of a black hole may be treated as a kind of Fowler-Nordheim field emission, which is the typical electron emission process from a metal surface under the action of an external electrostatic field. This type of emission from metal surface is allowed even at extremely low temperature. It has been noticed that in one-dimensional scenario, the Schrödinger equation satisfied by the created particle (anti-particle) near the event horizon, can be reduced to a differential form which is exactly identical with that obeyed by an electron immediately after the emission from the metal surface under the action of a strong electrostatic field. The mechanism of particle production near the event horizon of a black hole is therefore identified with Schwinger process in relativistic quantum field theory, whereas in the non-relativistic scenario it may be interpreted as Fowler-Nordheim emission process, when observed from a uniformly accelerated frame.

Abnormal difference between the mobilities of left- and right-twisted conformations of C6H12N2 roto-symmetrical molecules at very low temperatures.

We report an abnormal difference of low-temperature mobility of left-twisted and right-twisted conformations of roto symmetric molecules C6H12N2 (dabco) located in the same positions in crystal Zn2(C8H4O4)2⋅C6H12N2. The difference between (1)H NMR (Nuclear Magnetic Resonance) spin-relaxation data for left-twisted and right-twisted molecules reaches ∼3 × 10(3) times at 8 K and tends to grow at lower temperatures. We argue that taking into account four-component relativistic Dirac wave functions in the vicinity of the nodal plane of dabco molecules and vacuum fluctuations due to virtual particle-antiparticle pairs can explain the changes which C6H12N2 conformations undergo at low temperatures.

Dark-matter bound states from Feynman diagrams

If dark matter couples directly to a light force mediator, then it may form bound states in the early universe and in the non-relativistic environment of haloes today. In this work, we establish a field-theoretic framework for the computation of bound-state formation cross-sections, de-excitation and decay rates, in theories with long-range interactions. Using this formalism, we carry out specific computations for scalar particles interacting either via a light scalar or vector mediator. At low relative velocities of the interacting particles, the formation of bound states is enhanced by the Sommerfeld effect. For particle-antiparticle pairs, we show that bound-state formation can be faster than annihilation into radiation in the regime where the Sommerfeld effect is important. The field-theoretic formalism outlined here can be generalised to compute bound-state formation cross-sections in a variety of theories, including theories featuring non-Abelian (albeit non-confining) interactions, such as the electroweak interactions.

Wormholes and entanglement

Maldacena and Susskind have proposed a correspondence between wormholes and entanglement, dubbed ER=EPR. We study this in the context of three-dimensional topological quantum field theory (TQFT), where we show that the formation of a wormhole is the same process as creating a particle–antiparticle pair. A key feature of the ER=EPR proposal is that certain apparently entangled degrees of freedom turn out to be the same. We name this phenomenon ‘fake entanglement’, and show how it arises in our TQFT model.

Spin operator and entanglement in quantum field theory

Entanglement is studied in the framework of Dyson's S-matrix theory in relativistic quantum field theory, which leads to a natural definition of entangled states of a particle-antiparticle pair and the spin operator from a Noether current. As an explicit example, the decay of a massive pseudo-scalar particle into a pair of electron and positron is analyzed. Two spin operators are extracted from the Noether current. The Wigner spin operator characterizes spin states at the rest frame of each fermion and, although not measurable in the laboratory, gives rise to a straightforward generalization of low energy analysis of entanglement to the ultra-relativistic domain. In contrast, if one adopts a (modified) Dirac spin operator, the entanglement measured by spin correlation becomes maximal near the threshold of the decay, while the entanglement is replaced by the classical correlation for the ultra-relativistic electron-positron pair by analogy to the case of neutrinos, for which a hidden-variables-type description is possible. Chiral symmetry differentiates the spin angular momentum and the magnetic moment. The use of weak interaction that can measure helicity is suggested in the analysis of entanglement at high energies instead of a Stern-Gerlach apparatus which is useless for the electron. A difference between the electron spin at high energies and the photon linear polarization is also noted. The Standard Model can describe all the observable properties of leptons.

Microscopic wormholes and the geometry of entanglement

It has recently been suggested that Einstein–Rosen (ER) bridges can be interpreted as maximally entangled states of two black holes that form a complex Einstein–Podolsky–Rosen (EPR) pair. This relationship has been dubbed as the \(\textit{ER}=\textit{EPR}\) correlation. In this work, we consider the latter conjecture in the context of quadratic Palatini theory. An important result, which stems from the underlying assumptions as regards the geometry on which the theory is constructed, is the fact that all the charged solutions of the quadratic Palatini theory possess a wormhole structure. Our results show that spacetime may have a foam-like microstructure with wormholes generated by fluctuations of the quantum vacuum. This involves the spontaneous creation/annihilation of entangled particle–antiparticle pairs, existing in a maximally entangled state connected by a non-traversable wormhole. Since the particles are produced from the vacuum and therefore exist in a singlet state, they are necessarily entangled with one another. This gives further support to the \(\textit{ER}=\textit{EPR}\) claim.

Incompatibility of QED/QCD and repulsive gravity, and implications for some recent approaches to dark energy

The measurement of the gravitational properties of antimatter is currently a hot research area in experimental physics. Using an outcome of QED calculations by Alves et al. (arXiv:0907.4110, 2009), this letter proves that QED and repulsive gravity are incompatible by showing that an extension of QED with the assumption of negative gravitational mass for antimatter yields a concrete prediction that is already falsified by the recent Eot-Wash experiments: if repulsive gravity, and thus negative gravitational mass, would be observed by any of the upcoming experiments, then QED is thus experimentally falsified; the same goes for QCD. An immediate consequence is that virtual particle-antiparticle pairs from contemporary quantum theory cannot be a model for Hajdukovic’s virtual gravitational dipoles, nor for the dipolar medium of Blanchet and Le Tiec. There may be ways to reformulate quantum theory to restore consistency with experiment if repulsive gravity would be observed, but these involve a departure from the framework of four dimensions and four forces of nature: an observation of repulsive gravity would thus provide a reason to reject the quantum paradigm in its entirety and to search for new fundamental physics.

New research of charmonium over D $\bar D$ threshold using the antiproton beam with momentum ranging from 1 to 15 GeV/c

The spectroscopy of charmonium c \(\bar c\) is discussed. It is a good testing tool for the theories of strong interactions, including: QCD in both the perturbative and non-perturbative regimes, LQCD, potential models and phenomenological models. For this purpose an elaborated analysis of the charmonium spectrum is given, and attempts to interpret recent experimental data in the above D \(\bar D\) threshold region are considered. Experiments using antiproton beams take advantage of the intensive production of particle-antiparticle pairs in antiproton-proton annihilations. Experimental data from different collaborations are analyzed with special attention given to new states with hidden charm that were discovered recently. Some of these states can be interpreted as higher-laying S, P, and D wave charmonium states. But much more data on different decay modes are needed before firmer conclusions can be made. These data can be derived directly from the experiments using a high quality antiproton beam with momenta ranging from 1 to 15GeV/c.

A Simple Explanation of the Information Paradox by the Information Model of a Black Hole

The information paradox first surfaced in the early 1970s when Stephen Hawking of Cambridge University suggested that black holes are not totally black. Hawking showed that particle-antiparticle pairs generated at the event horizon—the outer periphery of a black hole—would be separated. One particle would fall into the black hole while the other would escape, making the black hole a radiating body. Characteristics of the emission and absorption of usual substance by a black hole can be described by information models. Estimation of the volume of information in black holes is necessary for generation of restrictions for their formation, development and interconversion. Information is an integral part of the Universe. By its physical essence information is heterogeneity of matter and energy. Therefore information is inseparably connected with matter and energy. An information approach along with a physical one allows to obtain new, sometimes more general data in relation to data obtained on the ground of physical rules only. The author’s works, testify about the practicality of information laws usage simultaneously with physical rules for cognition of the Universe. The results presented in this paper show the effectiveness of informational approach for studying the black holes. The article discusses the following questions: The volume of information in the black hole; Information model of a black hole; Characteristics of the emission and absorption of usual substance by a black hole describes the information model of a black hole; The information paradox; A simple explanation of the information paradox by the information model of a black hole.

Strongly enhanced pair production in combined high- and low-frequency laser fields

Production of particle-antiparticle pairs by a high-energy probe photon propagating through a high-intensity laser field is considered in the nonperturbative interaction regime. The laser field consists of a strong low-frequency and a weak high-frequency component. While for each component alone photoproduction of pairs is strongly suppressed, we show that their combination can largely amplify the pair production probability by facilitating to bridge the energetic barrier of the process. Our predictions can be tested by utilizing presently available high-intensity laser devices.

Charmonia and bottomonia in a magnetic field

We study the effect of a static homogeneous external magnetic field on charmonium and bottomonium states. In an external magnetic field, quarkonium states do not have a conserved center-of-mass momentum. Instead there is a new conserved quantity called the pseudomomentum which takes into account the Lorentz force on the particles in the system. When written in terms of the pseudomomentum, the internal and center-of-mass motions do not decouple and, as a result, the properties of quarkonia depend on the states' center-of-mass momentum. We analyze the behavior of heavy particle-antiparticle pairs subject to an external magnetic field assuming a three dimensional harmonic potential and Cornell potential plus spin-spin interaction. In the case of the Cornell potential, we also take into account the mixing of the eta_c and J/psi states and eta_b and Upsilon states due to the background magnetic field. We then numerically calculate the dependence of the masses and mixing fractions on the magnitude of the background magnetic field and center-of-mass momentum of the state.

STATISTICAL PROPERTIES OF A TRAPPED RELATIVISTIC FERMI GAS WITH PAIR PRODUCTION

Statistical properties of an ideal gas of relativistic fermions trapped in a D-dimensional power-law potential are studied, in which the effect of particle–antiparticle pair production is taken into account. It is shown that the relativistic effect is considerable even at very low temperatures for the system with Fermi energy comparable with the rest energy of a particle. In contrast, the effect of pair production is significant at high temperatures, but negligible at low temperatures. Moreover, it is found that the pair production results in several novel characteristics, such as the asymptotic behavior of chemical potential and rapid increase of heat capacity in the high temperature region.

Quarkonium and Bc mesons from Pb + Pb at LHC energies

The bb̄(Υ) mesons appear to be produced in the initial PbPb collision at 2.76 TeV per nucleon pair followed by partial melting in the hot quark-gluon plasma. In sharp contrast, the cc̄(J/Ψ) mesons seem more likely to be formed by recombination at the hadronization stage. The Bc mesons, with one quark of each kind are seldom seen in pp collisions because a particle-antiparticle pair requires the simultaneous production of four heavy quarks. Although a family of Bc mesons have been predicted, only the ground state has been seen. If the cc̄ mesons are produced by recombination, it could be expected that Bc mesons would be abundant with PbPb. Because the quark and antiquark have different flavor, the Bc are relatively long lived, 0.45 ps (to be compared with about 1.5 ps for the lighter B mesons). They would be seen with PbPb reactions by B±c → J/Ψ(μ+μ−)π± looking at muons and pions from displaced vertices.

Spectral study of the HESS J1745-290 gamma-ray source as dark matter signal

We study the main spectral features of the gamma-ray fluxes observed by the High Energy Stereoscopic System (HESS) from the J1745-290 Galactic Center source during the years 2004, 2005 and 2006. In particular, we show that these data are well fitted as the secondary gamma-rays photons generated from dark matter annihilating into Standard Model particles in combination with a simple power law background. We present explicit analyses for annihilation in a single standard model particle-antiparticle pair. In this case, the best fits are obtained for the uū and dd̄ quark channels and for the W+W− and ZZ gauge bosons, with background spectral index compatible with the Fermi-Large Area Telescope (LAT) data from the same region. The fits return a heavy WIMP, with a mass above ∼ 10 TeV, but well below the unitarity limit for thermal relic annihilation.

Geiger–Nuttall law for Schrödinger solitons

Based on the formal analogy between soliton tunneling through a classically forbidden potential barrier and –particle tunneling and decay we introduce a ‘toy solitonic model of a nucleus’ and show that the analog of the Geiger–Nuttall law can be discovered for Schrödinger solitons. We reveal and explain the analogy with virtual particle–antiparticle pair production and annihilation mechanisms and show how the nonlinear particle-like wave packet is being ‘dressed in a coat of virtual pairs’ and transformed into the soliton. In computational experiments with different soliton parameters and for different profiles of the barriers, including the charged sphere Coulomb potential, we demonstrate how the scaling symmetry breaking reveals the hidden role of the soliton self-interaction (binding) energy in the soliton scattering on external potentials and its dramatic impact on the wave-particle duality of solitons.