We present the solution of the Poincaré-covariant Faddeev equation for the ∆(1232) and Ω(1672) baryons. The covariant structure of the corresponding baryon amplitudes and their decomposition in terms of internal spin and orbital angular momentum is explicitly derived. The interaction kernel is truncated to a rainbow-ladder dressed-gluon exchange such that chiral symmetry and its dynamical breaking are correctly implemented. The resulting physical masses agree reasonably with experiment and their evolution with the pion mass compares favorably with lattice calculations. Evidence for the non-sphericity of the ∆−resonance is discussed as well.

The production of electron-positron pairs from the quantum vacuum polarized by the superposition of a strong and a perturbative oscillating electric field mode is studied. Our outcomes rely on a nonequilibrium quantum field theoretical approach, described by the quantum kinetic BoltzmannVlasov equation. By superimposing the perturbative mode, the characteristic resonant effects and Rabi-like frequencies in the single-particle distribution function are modified, as compared to the predictions resulting from the case driven by a strong oscillating field mode only. This is demonstrated in the momentum spectra of the produced pairs. Moreover, the dependence of the total number of pairs on the intensity parameter of each mode is discussed and a strong enhancement found for large values of the relative Keldysh parameter.

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 BoltzmannVlasov 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 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.

No abstract