Dynamical quark loop light-by-light contribution to muon g-2 within the nonlocal chiral quark model

The hadronic corrections to the muon anomalous magnetic moment a_mu, due to the gauge-invariant set of diagrams with dynamical quark loop light-by-light scattering insertions, are calculated in the framework of the nonlocal chiral quark model. These results complete calculations of all hadronic light-by-light scattering contributions to a_mu in the leading order in the 1/Nc expansion. The result for the quark loop contribution is a_mu^{HLbL,Loop}=(11.0+-0.9)*10^(-10), and the total result is a_mu^{HLbL,NxQM}=(16.8+-1.2)*10^(-10).Comment: 11 pages, 5 figures, 1 tabl

Vortex line representation for flows of ideal and viscous fluids

It is shown that the Euler hydrodynamics for vortical flows of an ideal fluid coincides with the equations of motion of a charged {\it compressible} fluid moving due to a self-consistent electromagnetic field. Transition to the Lagrangian description in a new hydrodynamics is equivalent for the original Euler equations to the mixed Lagrangian-Eulerian description - the vortex line representation (VLR). Due to compressibility of a "new" fluid the collapse of vortex lines can happen as the result of breaking (or overturning) of vortex lines. It is found that the Navier-Stokes equation in the vortex line representation can be reduced to the equation of the diffusive type for the Cauchy invariant with the diffusion tensor given by the metric of the VLR

Explicit Representations for the T-Matrix on Unphysical Energy Sheets and Resonances in Two- and Three-Body Systems

We discuss the structure of the two- and three-body T-matrices, scattering matrices, and resolvents continued to the unphysical energy sheets. Our conclusions arise due to the representations that have been found for analytically continued momentum-space kernels of the T-operators. These representations are explicitly written only in terms of the physical-sheet kernels of the T-matrix itself. One of advantages of the representations in the three-body case is that they show which portions of the physical-sheet three-body scattering matrix are ``responsible'' for the resonances associated with a particular unphysical sheet. A resonance appears to be the energy where the correspondingly truncated scattering matrix (taken on the physical sheet) has eigenvalue zero. We also mention applications of this approach to some specific three-body systems, based on the Faddeev differential equations.Comment: Based on a lecture given at the International Workshop ``Critical Stability of Few-Body Quantum Systems'' (Dresden, October 17--22, 2005

Vacuum Energy: Myths and Reality

We discuss the main myths related to the vacuum energy and cosmological constant, such as: ``unbearable lightness of space-time''; the dominating contribution of zero point energy of quantum fields to the vacuum energy; non-zero vacuum energy of the false vacuum; dependence of the vacuum energy on the overall shift of energy; the absolute value of energy only has significance for gravity; the vacuum energy depends on the vacuum content; cosmological constant changes after the phase transition; zero-point energy of the vacuum between the plates in Casimir effect must gravitate, that is why the zero-point energy in the vacuum outside the plates must also gravitate; etc. All these and some other conjectures appear to be wrong when one considers the thermodynamics of the ground state of the quantum many-body system, which mimics macroscopic thermodynamics of quantum vacuum. In particular, in spite of the ultraviolet divergence of the zero-point energy, the natural value of the vacuum energy is comparable with the observed dark energy. That is why the vacuum energy is the plausible candidate for the dark energy.Comment: 24 pages, 2 figures, submitted to the special issue of Int. J. Mod. Phys. devoted to dark energy and dark matter, IJMP styl