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Within the geometric optics approximation, we derive the light cone condition for a class of homogeneous non-trivial QED vacua using the effective action approach. Our result generalizes the “unified formula” suggested by Latorre, Pascual and Tarrach which turns out to be a low-energy limit. We calculate the velocity shifts induced by electromagnetic fields(More)
We analyze the possibility of nonperturbative renormalizability of gauge theories in D.4 dimensions. We develop a scenario, based on Weinberg’s idea of asymptotic safety, that allows for renormalizability in extra dimensions owing to a non-Gaussian ultraviolet stable fixed point. Our scenario predicts a critical dimension Dcr beyond which the UV fixed point(More)
Possible extensions of the standard model of particle physics suggest the existence of particles with small, unquantized electric charge. Photon-initiated pair production of millicharged fermions in a magnetic field would manifest itself as a vacuum magnetic (VM) dichroism. We show that laser polarization experiments searching for this effect yield, in the(More)
We compute Casimir interaction energies for the sphere-plate and cylinder-plate configuration induced by scalar-field fluctuations with Dirichlet boundary conditions. Based on a high-precision calculation using world-line numerics, we quantitatively determine the validity bounds of the proximity-force approximation (PFA) on which the comparison between all(More)
We employ the recently developed worldline numerics, which combines string-inspired field theory methods with Monte Carlo techniques, to develop an algorithm for the computation of pair-production rates in scalar QED for inhomogeneous background fields. We test the algorithm with the classic Sauter potential, for which we compute the local production rate(More)
The derivation of a convergent series representation for the quantum electrodynamic effective action obtained by two of us (is reexamined. We present more details of our original derivation. Moreover, we discuss the relation of the electric-magnetic duality to the integral representation for the effective action, and we consider the application of nonlinear(More)
As an application of the QED effective action approach at finite temperature [1]-[5], we investigate the aberration of low-frequency photons from the usual vacuum light cone in the presence of a heat bath. The propagation of photons can deviate from the classically free vacuum behavior when external perturbations exert their influence on the vacuum(More)