We study massive charged particle production from the vacuum confined between two vibrating plates in the presence of a strong electric field. We analytically derive a formula for the production number based on the perturbation theory in the Furry picture, and show that the Schwinger mechanism by the strong electric field and the dynamical Casimir effect by the vibration assist with each other to dramatically enhance the production number by orders of the magnitude.
Schwinger's Dynamical Casimir Effect is one of several candidate explanations for sonoluminescence. Recently, several papers have claimed that Schwinger's estimate of the Casimir energy involved is grossly inaccurate. In this letter, we show that these calculations omit the crucial volume term. When the missing term is correctly included one finds full agreement with Schwinger's result for the Dynamical Casimir Effect. We have nothing new to say about sonoluminescence itself except to affirm that the Casimir effect is energetically adequate as a candidate explanation.
We study particle and chirality production from the vacuum in the presence of a slow strong parallel electromagnetic field superimposed by a fast weak perturbative electromagnetic field. We derive an analytical formula for the particle and chirality production number based on the perturbation theory in the Furry picture. With the formula, we analytically discuss the interplay and dynamical assistance between the Schwinger mechanism and one-photon pair production and clarify effects of a parallel slow strong magnetic field. We also show that the dynamical assistance can significantly enhance ch…
Julian Schwinger began the construction of Source Theory in 1966 in response to the then apparent failure of quantum field theory to describe strong interactions, the physical remoteness of renormalization, and the utility of effective actions in describing chiral dynamics. I will argue that the source theory development was not really so abrupt a break with the past as Julian may have implied, for the ideas and techniques in large measure were present in his work at least as early as 1951. Those techniques and ideas are still of fundamental importance to theoretical physics, so much so that t…
Bound-free electron-positron pair production in combined Coulomb and constant crossed electromagnetic fields: a Schwinger-like process with intrinsic assistance
We study both massless scalar and Yang-Mills field theories in the deep infrared in presence of a simple boundary. We can show, with the help of the recent scenario emerging from studies on the propagators, that the presence of a mass gap makes the Casimir contribution exponentially small as should be expected. We obtain our result from the solution of the Dyson-Schwinger set of equations obtained in form of partial differential equations. Our results agree fairly well with recent lattice computations.
Several years ago Schwinger proposed a physical mechanism for sonoluminescence in terms of photon production due to changes in the properties of the quantum-electrodynamic (QED) vacuum arising from a collapsing dielectric bubble. This mechanism can be re-phrased in terms of the Casimir effect and has recently been the subject of considerable controversy. The present paper probes Schwinger's suggestion in detail: Using the sudden approximation we calculate Bogolubov coefficients relating the QED vacuum in the presence of the expanded bubble to that in the presence of the collapsed bubble. In th…
In the final few years of his life, Julian Schwinger proposed that the ``dynamical Casimir effect'' might provide the driving force behind the puzzling phenomenon of sonoluminescence. Motivated by that exciting suggestion, we have computed the static Casimir energy of a spherical cavity in an otherwise uniform material. As expected the result is divergent; yet a plausible finite answer is extracted, in the leading uniform asymptotic approximation. This result agrees with that found using zeta-function regularization. Numerically, we find far too small an energy to account for the large burst o…
We obtain an exact result for the non-perturbative quark (antiquark) production rate and its p_T distribution from a constant SU(3) chromo-electric field E^a with arbitary color index $a$ by directly evaluating the path integral. Unlike the WKB tunneling result, which depends only on one gauge invariant quantity |E|, the strength of the chromo-electric field, we find that the exact result for the p_T distribution for quark (antiquark) production rate depends on two independent Casimir (gauge) invariants, E^aE^a and [d_{abc}E^aE^bE^c]^2.
It is shown that the commonly accepted definition for the Casimir scalar operators of the Poincare group does not satisfy the properties of Casimir invariance when applied to the non-inertial motion of elementary particles while in the presence of external gravitational and electromagnetic fields, where general curvilinear co-ordinates are used to describe the momentum generators within a Fermi normal co-ordinate framework. Specific expressions of the Casimir scalar properties are presented for spin-1/2 to spin-2 particles inclusive. While the Casimir scalar for linear momentum remains a Loren…
We study the Schwinger mechanism in QCD in the presence of an arbitrary time-dependent chromo-electric background field $E^a(t)$ with arbitrary color index $a$=1,2,...8 in SU(3). We obtain an exact result for the non-perturbative quark (antiquark) production from an arbitrary $E^a(t)$ by directly evaluating the path integral. We find that the exact result is independent of all the time derivatives $\frac{d^nE^a(t)}{dt^n}$ where $n=1,2,...\infty$. This result has the same functional dependence on two Casimir invariants $[E^a(t)E^a(t)]$ and $[d_{abc}E^a(t)E^b(t)E^c(t)]^2$ as the constant chromo-…
The assistance of an intense optical laser pulse on electron-positron pair production by the Breit-Wheeler and Schwinger processes in XFEL fields is analyzed. The impact of a laser beam on high-energy photon collisions with XFEL photons consists in a phase space redistribution of the pairs emerging in the Breit-Wheeler sub-process. We provide numerical examples of the differential cross section for parameters related to the European XFEL. Analogously, the Schwinger type pair production in pulsed fields with oscillating components referring to a superposition of optical laser and XFEL frequenci…
Electron-positron pair production from vacuum in external electric fields with space and time dependencies is studied numerically using real time Dirac-Heisenberg-Wigner formalism. The influence of spatial focusing scale of the electric field on momentum distribution and the total yield of the particles is examined by considering standing wave mode of the electric field with different temporal configurations. With the decrease of spatial extent of the external field, signatures of the temporal field are weaken in the momentum spectrum. Moreover, in the extremely small spatial extent, novel fea…
We investigate the phenomenon of electron-positron pair production from vacuum in the presence of a strong electric field superimposed by a weak but fast varying pulse which substantially increases the total particle yield. We employ a nonperturbative numerical technique and perform the calculations beyond the spatially-uniform-field approximation, i.e. dipole approximation, taking into account the coordinate dependence of the fast component. The analysis of the main characteristics of the pair-production process (momentum spectra of particles and total amount of pairs) reveals a number of imp…
The phenomenon of sonoluminescence (SL), originally observed some sixty years ago, has recently become the focus of renewed interest, particularly with the discovery that one can trap a single bubble and induce it to exhibit SL stably over a large number of acoustical cycles. In this work we shall adopt a version of the provocative suggestion put forward by Schwinger: the mechanism responsible for the radiation in SL is a dynamic version of the Casimir effect. It has been known since Casimir's original work in 1948 that the zero-point energy of quantum fields can be modified by the presence of…
We study Schwinger mechanism for gluon pair production in the presence of arbitrary time-dependent chromo-electric background field $E^a(t)$ with arbitrary color index $a$=1,2,...8 in SU(3) by directly evaluating the path integral. We obtain an exact expression for the probability of non-perturbative gluon pair production per unit time per unit volume and per unit transverse momentum $\frac{dW}{d^4x d^2p_T}$ from arbitrary $E^a(t)$. We show that the tadpole (or single gluon) effective action does not contribute to the non-perturbative gluon pair production rate $\frac{dW}{d^4x d^2p_T}$. We fin…
Several years ago Schwinger proposed a physical mechanism for sonoluminescence in terms of changes in the properties of the quantum-electrodynamic (QED) vacuum state. This mechanism is most often phrased in terms of changes in the Casimir Energy: changes in the distribution of zero-point energies and has recently been the subject of considerable controversy. The present paper further develops this quantum-vacuum approach to sonoluminescence: We calculate Bogolubov coefficients relating the QED vacuum states in the presence of a homogeneous medium of changing dielectric constant. In this way we…
In the dynamically assisted Schwinger mechanism, the pair production probability is significantly enhanced by including a weak, rapidly varying field in addition to a strong, slowly varying field. In a previous paper we showed that several features of dynamical assistance can be understood by a perturbative treatment of the weak field. Here we show how to calculate the prefactors of the higher-orders terms, which is important because the dominant contribution can come from higher orders. We give a new and independent derivation of the momentum spectrum using the worldline formalism, and extend…
The infrared behavior of the quark-gluon vertex of quenched Landau gauge QCD is studied by analyzing its Dyson-Schwinger equation. Building on previously obtained results for Green functions in the Yang-Mills sector we analytically derive the existence of power-law infrared singularities for this vertex. We establish that dynamical chiral symmetry breaking leads to the self-consistent generation of components of the quark-gluon vertex forbidden when chiral symmetry is forced to stay in the Wigner-Weyl mode. In the latter case the running strong coupling assumes an infrared fixed point. If chir…
