We show how to do semiclassical nonperturbative computations within the worldline approach quantum field theory using ``worldline instantons''. These instantons are classical solutions Euclidean loop equations of motion, and closed spacetime loops parametrized by proper-time. Specifically, we compute imaginary part one effective action in scalar QED instantons'', for a wide class inhomogeneous electric backgrounds. treat both time dependent space fields, note that temporal inhomogeneities...

In a previous paper [G. V. Dunne and C. Schubert, Phys. Rev. D 72, 105004 (2005).], it was shown that the worldline expression for nonperturbative imaginary part of QED effective action can be approximated by contribution special closed classical path in Euclidean spacetime, known as instanton. Here we extend this formalism to compute also prefactor arising from quantum fluctuations about path. We present direct numerical approach determining prefactor, find simple explicit formula cases...

We recalculate the amplitude for photon splitting in a strong magnetic field below pair production threshold, using world line path integral variant of Bern-Kosower formalism. Numerical comparison (using programs that we have made available public access on Internet) shows results recalculation are identical to earlier calculations Adler and later Stoneham, recent by Baier, Milstein, Shaisultanov.

We consider thick brane configurations in a pure geometric Weyl integrable 5D space-time, non-Riemannian generalization of Kaluza-Klein (KK) theory involving scalar field. Thus, the describes gravity coupled to self-interacting field which gives rise structure branes. continue study properties previously found family solutions is smooth at position but involves naked singularities fifth dimension. Analyzing their graviton spectrum, we find that particularly interesting situation arises for...

Perturbative quantum field theory usually uses second quantisation and Feynman diagrams. The worldline formalism provides an alternative approach based on first quantised particle path integrals, similar in spirit to string perturbation theory. Here we review the history, main features present applications of formalism. Our emphasis is recent developments such as integral representation open fermion lines, description colour using auxiliary fields, incorporation higher spin, extension...

We use different methods to calculate the imaginary part of gravitational effective action due a massless scalar field, with view on perturbative vs nonpertubative and results Wondrak [Gravitational pair production black hole evaporation, ]. Published by American Physical Society 2024

We use the world line path-integral approach to Bern-Kosower formalism for developing a new algorithm calculation of sum diagrams with one spinor loop and fixed number external internal photons. The method is based on supersymmetry, construction generalized Green functions. two-loop QED \ensuremath{\beta} function calculated as an example. \textcopyright{} 1996 American Physical Society.

We present a new method for the derivation of convolution identities finite sums products Bernoulli numbers.Our approach is motivated by role these in quantum field theory and string theory.We first show that Miki identity Faber-Pandharipande-Zagier (FPZ) are closely related, give simple unified proofs which naturally yield number identity.We then generalize each three into families depending on continuous parameter.We rederive cubic generalization Miki's due to Gessel obtain similar...

We apply the worldline formalism to amplitudes in scalar quantum electrodynamics involving open lines, with an emphasis on their nonperturbative gauge dependence. At tree level, we study propagator interacting any number of photons configuration space as well momentum space. one loop rederive, efficient way, off-shell vertex arbitrary dimension and covariant gauge. Generalizing Landau-Khalatnikov-Fradkin transformation for propagator, find simple rules $x$-space under a change parameter...

In the first-quantised worldline approach to quantum field theory, a long-standing problem has been extend this formalism amplitudes involving open fermion lines while maintaining efficiency of well-tested closed-loop case. present series papers, we develop suitable for case electrodynamics in vacuum (part one and two) constant external electromagnetic three), based on second-order fermions symbol map. We derive from standard but also give an alternative derivation intrinsic theory. first...

The QED four-photon amplitude has been well-studied by many authors, and on-shell is treated in textbooks. However, a calculation with all four photons off-shell presently still lacking, despite of the fact that this appears as subprocess different contexts, vacuum well some connecting to external fields. present paper first series where we use worldline formalism obtain explicitly terms hypergeometric functions, derivatives thereof, for both scalar spinor QED. allows us unify loop...

This paper examines the relationship between art and life in works of Friedrich Nietzsche. While Nietzscheʼs topos “art living” has often been explored as an ethos self-formation, specific connection with various arts is overlooked. Both actor painter become role models whose techniques are suggested useful strategies. Scholars overlook that Nietzsche corrects his earlier metaphysical ideas according to which justifying and, on contrary, places middle no longer beyond it. usually seen...