The Wilson loop from a Dyson equation

The Dyson equation proposed for planar temporal Wilson loops in the context of supersymmetric gauge theories is critically analysed thereby exhibiting its ingredients and approximations involved. We reveal its limitations and identify its range of applicability in non-supersymmetric gauge theories. In particular, we show that this equation is applicable only to strongly asymmetric planar Wilson loops (consisting of a long and a short pair of loop segments) and as a consequence the Wilsonian potential can be extracted only up to intermediate distances. By this equation the Wilson loop is exclusively determined by the gluon propagator. We solve the Dyson equation in Coulomb gauge for the temporal Wilson loop with the instantaneous part of the gluon propagator and for the spatial Wilson loop with the static gluon propagator obtained in the Hamiltonian approach to continuum Yang-Mills theory and on the lattice. In both cases we find a linearly rising color potential.Comment: 12 pages, 7 figure

Cho and Pak reply to Lamm et al. comment on "A Convergent Series for the QED Effective Action"

Cho and Pak reply to Lamm et al. [hep-th/0007108] comment on "A Convergent Series for the Effective Action of QED" [hep-th/0006057].Comment: 1 pag

Evidence for a new SU(4)SU(4) symmetry with J=2J=2 mesons

Recently, a new symmetry of mesons has been found upon truncation of the quasi-zero modes of the Overlap Dirac operator in lattice simulations. Namely, the $\rho,\rho',\omega,\omega',a_1, b_1,h_1$ and possibly $f_1$ $J=1$ mesons get degenerate after removal of the quasi-zero modes. This emergent symmetry has been established to be $SU(4)\supset SU(2)_L \times SU(2)_R \times U(1)_A$. It is higher than the symmetry of the QCD Lagrangian and provides not only a mixing of quarks of given chirality in the isospin space, but also the mixing of left-handed and right-handed components. Here we study, with the Overlap Dirac operator, the isovector $J=2$ mesons upon the quasi-zero mode reduction and observe a similar degeneracy. This result further supports the $SU(4)$ symmetry in mesons of given spin $J \geq 1$.Comment: 6 figure

Vacuum tunneling in gravity

Topologically non-trivial vacuum structure in gravity models with Cartan variables (vielbein and contortion) is considered. We study the possibility of vacuum space-time tunneling in Einstein gravity assuming that the vielbein may play a fundamental role in quantum gravitational phenomena. It has been shown that in the case of RP3 space topology the tunneling between non-trivial topological vacuums can be realized by means of Eguchi-Hanson gravitational instanton. In Riemann-Cartan geometric approach to quantum gravity the vacuum tunneling can be provided by means of contortion quantum fluctuations. We define double self-duality condition for the contortion and give explicit self-dual configurations which can contribute to vacuum tunneling amplitude.Comment: 11 pages, 1 fig. is added, final versio

Rare Radiative B -> tau^+ tau^- gamma Decay

The radiative B -> tau^+ tau^- gamma decay is investigated in the framework of the Standard Model. When only short (short and long together) distance contributions are taken into account, the Branching Ratio is found as 9.54x10^(-9) (1.52x10^(-8)), for the value of the cut delta = 0.01 imposed on the photon energy.Comment: 14 pages, 2 figures, LaTeX formatte