Additional Four-fermion Interaction Research Articles

Finite density QCD with chiral-invariant four-fermion interactions

A mean field analysis of finite density QCD is presented including the effects of additional chiral-invariant four-fermion interactions. A lattice regularization is used with ${N}_{f}=4$ flavors of staggered fermions. The use of the four-fermion coupling as an improved extrapolation parameter over the bare quark mass in Monte Carlo simulations is discussed. Particular attention is given to the structure of the phase diagram and the order of the chiral phase transition. At zero gauge coupling, the model reduces to a Nambu--Jona-Lasinio model. In this limit the chiral phase transition is found to be second-order near the zero-density critical point and otherwise first order. In the strong gauge coupling limit a first-order chiral phase transition is found. In this limit the additional four-fermion interactions do not qualitatively change the physics. The results agree with previous studies of QCD as the four-fermion coupling vanishes.

Erratum: Green's functions of composite operators and bound states in gauge theories

The formalism for the description of Green's functions of composite operators on the nonperturbative vacuum is proposed. In the ladder approximation the formalism is applied to determine Green's functions of the operators F/sub ..mu..//sub ..nu../F/sup ..mu..//sup ..nu../, psi-barlambda/sup a/psi, psi-bar..gamma../sub 5/lambda/sup a/psi in vectorlike gauge theories. The properties of scalar and pseudoscalar bound states in gauge theories and in gauge theories with an additional four-fermion interaction are considered. The dynamics in the regime with the nontrivial fixed point is discussed.

Critical Line and Beta Functions in Abelian Gauge Theories with Additional Four-Fermion Interactions

Using the Bethe-Salpeter equation for electron-positron bound states in quantum electrodynamics with four-fermion interactions we obtain the critical line which separates the chiral symmetric and broken phase. We calculate the nonperturbative beta functions near the critical line in the broken phase.

ON THE PHASE DIAGRAM OF ASYMPTOTICALLY FREE GAUGE THEORIES WITH ADDITIONAL FOUR-FERMION INTERACTION

In the ladder asymptotically free gauge models with one-loop running coupling constant and additional four-fermion interaction, the structure of the phase diagram in coupling constants is determined. The anomalous dimension γm of the composite operator [Formula: see text] is calculated on the full critical line of the diagram. The possibilities of the examination of the phase diagram of such theories in lattice computer simulations are discussed.

Green's functions of composite operators and bound states in gauge theories.

The formalism for the description of Green's functions of composite operators on the nonperturbative vacuum is proposed. In the ladder approximation the formalism is applied to determine Green's functions of the operators F/sub ..mu..//sub ..nu../F/sup ..mu..//sup ..nu../, psi-barlambda/sup a/psi, psi-bar..gamma../sub 5/lambda/sup a/psi in vectorlike gauge theories. The properties of scalar and pseudoscalar bound states in gauge theories and in gauge theories with an additional four-fermion interaction are considered. The dynamics in the regime with the nontrivial fixed point is discussed.

CRITICAL LINE AND BETHE-SALPETER EQUATION IN STRONG-COUPLING QED WITH FOUR-FERMION INTERACTIONS

On the basis of Bethe-Salpeter equations for electron-positron bound states in strong-coupling quantum electrodynamics with additional four-fermion interactions, the formula for the critical line dividing the chiral-symmetry-breaking phase from the symmetric phase is derived. The beta functions near the critical line are calculated explicitly and the phase structure is discussed based on these beta functions.

On the spectrum of excitations in some strong coupling gauge models

The spectrum of spinless excitations in (3+1)-dimensional ladder QED with additional four-fermion interaction and in (2+1)-dimensional QED is considered.