Dependence of the crossover zone on the regularization method in the two-flavor Nambu–Jona-Lasinio model

In this article, we study the two-flavor Nambu and Jona-Lasinio (NJL) phase diagrams on the T–μ plane through three regularization methods. In one of these, we introduce an infrared three-momentum cutoff in addition to the usual ultraviolet regularization to the quark loop integrals and compare the obtained phase diagrams with those obtained from the NJL model with proper time regularization and Pauli–Villars regularization. We have found that the crossover appears as a band with a well-defined width in the T–μ plane. To determine the extension of the crossover zone, we propose a novel criterion, comparing it to another criterion that is commonly reported in the literature; we then obtain the phase diagrams for each criterion. We study the behavior of the phase diagrams under all these schemes, focusing on the influence of the regularization procedure on the crossover zone and the presence or absence of critical end points.

Light front Hamiltonian for boson form of QED (1 + 1) in Pauli–Villars regularization

Light front (LF) Hamiltonian for QED in [Formula: see text] dimensions is constructed using the boson form of this model with additional Pauli–Villars-type ultraviolet regularization. Perturbation theory, generated by this LF Hamiltonian, is proved to be equivalent to usual covariant chiral perturbation theory. The obtained LF Hamiltonian depends explicitly on chiral condensate parameters which enter in a form of some renormalization of coupling constants. The obtained results can be useful when one attempts to apply LF Hamiltonian approach for [Formula: see text]-dimensional models like QCD.

FEYNMAN PERTURBATION THEORY FOR GAUGE THEORY ON TRANSVERSE LATTICE

Feynman perturbation theory for non-Abelian gauge theory in light-like gauge is investigated. A lattice along two spacelike directions is used as a gauge invariant ultraviolet regularization. For preservation of the polynomiality of action, we use as independent variables arbitrary (nonunitary) matrices related to the link of the lattice. The action of the theory is selected in such a way to preserve as much as possible the rotational invariance, which remains after an introduction of the lattice, as well as to make superfluous degrees of freedom vanish in the limit of removing the regularization. Feynman perturbation theory is constructed and diagrams which does not contain ultraviolet divergences are analyzed. The scheme of renormalization of this theory is discussed.

EFFECTIVE ACTION OF DRESSED MEAN FIELDS FOR $\mathcal{N}=4$ SUPER-YANG–MILLS THEORY

Based on general considerations such as R-operation and Slavnov–Taylor identity we show that the effective action, being understood as Legendre transform of the logarithm of the path integral, possesses particular structure in [Formula: see text] supersymmetric Yang–Mills theory for kernels of the effective action expressed in terms of the dressed effective fields. These dressed effective fields have been introduced in our previous papers as actual variables of the effective action. The concept of dressed effective fields naturally appears in the framework of solution to Slavnov–Taylor identity. The particularity of the structure is the independence of these kernels on the ultraviolet regularization scale Λ. These kernels are functions of mutual spacetime distances and of the gauge coupling. The fact that β function in this theory is zero is used significantly.

PATH INTEGRAL TREATMENT OF SINGULAR PROBLEMS AND BOUND STATES

A path-integral approach for the computation of quantum-mechanical propagators and energy Green's functions is presented. Its effectiveness is demonstrated through its application to singular interactions, with particular emphasis on the inverse square potential — possibly combined with a delta-function interaction. The emergence of these singular potentials as low-energy nonrelativistic limits of quantum field theory is highlighted. Not surprisingly, the analog of ultraviolet regularization is required for the interpretation of these singular problems.