D. G. Pak

Monopole condensation in SU(2) QCD

We review the quantum instability of the Savvidy-Nielsen-Olesen (SNO) vacuum of the one-loop effective action of SU(2) QCD, and point out a critical defect in the calculation of the functional determinant of the gluon loop in the SNO effective action. We prove that the gauge invariance, in particular the color reflection invariance, exclude the unstable tachyonic modes from the gluon loop integral. This guarantees the stability of the magnetic condensation in QCD.

Faddeev-Niemi conjecture and effective action of QCD

We calculate a one loop effective action of SU(2) QCD in the presence of the monopole background, and find a possible connection between the resulting QCD effective action and a generalized Skyrme–Faddeev action of the non-linear sigma model. The result is obtained using the gauge-independent decomposition of the gauge potential into the topological degrees which describes the non-Abelian monopoles and the local dynamical degrees of the potential, and integrating out all the dynamical degrees of QCD.

Monopole condensation and dimensional transmutation in SU(2) QCD

We resolve the controversy on the stability of the monopole condensation in the one-loop effective action of SU(2) QCD by calculating the imaginary part of the effective action with two different methods at one-loop order. Our result confirms that the effective action for the magnetic background has no imaginary part but the one for the electric background has a negative imaginary part. This assures that the monopole condensation is indeed stable, but the electric background becomes unstable due to the pair-annihilation of gluons.We resolve the controversy on the stability of the monopole condensation in the one-loop effective action of SU(2) QCD by calculating the imaginary part of the effective action with two different methods at one-loop order. Our result confirms that the effective action for the magnetic background has no imaginary part but the one for the electric background has a negative imaginary part. This assures that the monopole condensation is indeed stable, but the electric background becomes unstable due to the pair-annihilation of gluons.

A Convergent Series for the QED Effective Action

The one-loop effective action of QED obtained by Euler and Heisenberg and by Schwinger has been expressed by an asymptotic perturbative series which is divergent. In this letter we present a non-perturbative but convergent series of the effective action. With the convergent series we establish the existence of the manifest electric-magnetic duality in the one loop effective action of QED.The one-loop effective action of QED obtained by Euler and Heisenberg and by Schwinger has been expressed by an asymptotic perturbative series which is divergent. In this letter we present a non-perturbative but convergent series of the effective action. With the convergent series we establish the existence of the manifest electric-magnetic duality in the one loop effective action of QED.

On gauge invariant nucleon spin decomposition

A non-uniqueness problem of gauge invariant separation of quark and gluon contributions to nucleon spin is considered. We show that there is a wide number of gauge invariant spin decompositions, and each of them reduces to the canonical one in a special gauge. A class of physical gauge equivalent nucleon spin decompositions is selected by requirements of consistence with helicity notion described within the E(2) little group representation theory and with the gluon helicity Δg measured in the experiment.

Topologically massive gauge theories in superspace

This paper presents a study of the geometrical properties of superfield D=3, N=1, 2 Yang-Mills theories, and derives explicit expressions for the topological mass term. In the case of the D=3, N=1 theory, the subject is addressed in the language of differential forms, and a special mapping of the Chern-Simons class of differential forms into the corresponding class of integral forms is used to construct the topological mass term. A superfield description is given for the D=3, N=2 Yang-Mills theory that arises upon dimensional reduction of the corresponding four-dimensional theory with N=1 supersymmetry. The expression for the topological mass term is derived in compact form in prepotential terms.

QCD EFFECTIVE ACTION WITH A MOST GENERAL HOMOGENEOUS FIELD BACKGROUND

We consider one-loop effective action of SU(3) QCD with a most general constant chromomagnetic (chromoelectric) background which has two independent Abelian field components. The effective potential with a pure magnetic background has a local minimum only when two Abelian components

Stable monopole–antimonopole string background in SU(2) QCD

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Knot soliton in Weinberg–Salam model

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A MINIMAL MODEL OF LORENTZ GAUGE GRAVITY WITH DYNAMICAL TORSION

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