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Register a new userMaster formulas for the dressed scalar propagator in a constant field
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The worldline formalism has previously been used for deriving compact master formulas for the one-loop N-photon amplitudes in both scalar and spinor QED, and in the vacuum as well as in a constant external field. For scalar QED, there is also an analogous master formula for the propagator dressed with N photons in the vacuum. Here, we extend this master formula to include a constant field. The two-photon case is worked out explicitly, yielding an integral representation for the Compton scattering cross section in the field suitable for numerical integration in the full range of electric and magnetic field strengths.
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It is emphasized that for interactions with derivative couplings, the Ward Identity (WI) securing the preservation of a global U(1) symmetry should be modified. Scalar QED is taken as an explicit example. More precisely, it is rigorously shown in scalar QED that the naive WI and the improved Ward Identity (Master Ward Identity, MWI) are related to each other by a finite renormalization of the time-ordered product (T-product) for the derivative fields; and we point out that the MWI has advantages over the naive WI - in particular with regard to the proof of the MWI. We show that the MWI can be fulfilled in all orders of perturbation theory by an appropriate renormalization of the T-product, without conflict with other standard renormalization conditions. Relations with other recent formulations of the MWI are established.
We isolate the two-step mechanism involving a real intermediate photon from the one-step mechanism involving a virtual photon for the trident process in a constant crossed field. The two-step process is shown to agree with an integration over polarised sub-processes. At low to moderate quantum non-linearity parameter, the one-step process is found to be suppressed. When the parameter is large, the two decay channels are comparable if the field dimensions are not much greater than the formation length.
We apply the exponential operator method to derive the propagator for a fermion immersed within a rigidly rotating environment with cylindrical geometry. Given that the rotation axis provides a preferred direction, Lorentz symmetry is lost and the general solution is not translationally invariant in the radial coordinate. However, under the approximation that the fermion is completely dragged by the vortical motion, valid for large angular velocities, translation invariance is recovered. The propagator can then be written in momentum space. The result is suited to be used applying ordinary Feynman rules for perturbative calculations in momentum space.
The present work aims to explore the model given by Lanczos-Lovelock gravity theories indexed by a fixed integer to require a unique anti-de Sitter vacuum, dressed by a scalar field non-minimal coupling. For this model, we add a special matter source characterized by a non-linear Maxwell field coupling with a function depending on the scalar field. Computing its thermodynamics parameters by using the Euclidean action, we obtain interesting and non zero thermodynamical quantities, unlike its original version, allowing analyzing thermodynamical stability. Together with the above, we found that these solutions satisfy the First Law of Thermodynamics as well as a Smarr relation.
We investigate the equal-time (static) quark propagator in Coulomb gauge within the Hamiltonian approach to QCD. We use a non-Gaussian vacuum wave functional which includes the coupling of the quarks to the spatial gluons. The expectation value of the QCD Hamiltonian is expressed by the variational kernels of the vacuum wave functional by using the canonical recursive Dyson--Schwinger equations (CRDSEs) derived previously. Assuming the Gribov formula for the gluon energy we solve the CRDSE for the quark propagator in the bare-vertex approximation together with the variational equations of the quark sector. Within our approximation the quark propagator is fairly insensitive to the coupling to the spatial gluons and its infrared behaviour is exclusively determined by the strongly infrared diverging instantaneous colour Coulomb potential.
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