Dispersive and chiral symmetry constraints on the light meson form factors

The form factors of the light pseudoscalar mesons are investigated in a dispersive formalism based on hadronic unitarity, analyticity and the OPE expansion of the QCD Green functions. We propose generalizations of the original mathematical techniques, suitable for including additional low energy information provided by experiment or Chiral Perturbation Theory (CHPT). The simultaneous treatment of the electroweak form factors of the and K mesons allows us to test the consistency with QCD of a low energy CHPT theorem. By applying the formalism to the pion electromagnetic form factor, we derive quite strong constraints on the higher Taylor coefficients at zero momentum, using information about the phase and the modulus of the form factor along a part of the unitarity cut. Received: 16 July 1999 / Published online: 6 March 2000     

On the chiral hubbard model and the chiral Kondo lattice model

The integrability of the one-dimensional chiral Hubbard model is discussed in the limit of strong interaction,U=. The system is shown to be integrable in the sense of the existence of an infinite number of constants of motion. The system is related to a chiral Kondo lattice model at strong interactionJ=+.     

On the stability of the chiral vacuum

Zeitschrift für Physik C Particles and Fields - The stability of the chiral vacuum is explored in Coulomb gauge QCD, in the Breit frame. We find that perturbative Coulomb and transverse gluon...     

On the BRST quantization of chiral bosons

The Siegel action for two right-moving chiral bosons can be BRST quantized. In the case in which their kinetic terms have opposite signs the momenta in the left-moving sector must be constrained to be zero. In this case the two chiral bosons can be described also by a quadratic action. There is no analogous BRST quantization for a single chiral boson.     

On the connection between the principal chiral model and the multiflavour chiral Gross-Neveu model

The infinite flavour limit of the multiflavour chiral Gross-Neveu (MCGN) partition function is shown to be equal to the principal chiral σ-model (PCM) partition function where in addition one integrates over twisted boundary conditions. This last interpretation restricts the space of states to the left (or right) singlet sector. In the course of this derivation, a rigorous paramagnetic inequality for the Dirac determinant is proved. The critical (conformal invariant) points of the MCGN are investigated in connection with critical WZW σ-models.     

On the chiral anomaly in non-Riemannian spacetimes

Thetranslation Chern-Simons type three-formcoframe∧torsion on a Riemann-Cartan spacetime is related (by differentiation) to the Nieh-Yan fourform. Following Chandia and Zanelli, two spaces with nontrivial translational Chern-Simons forms are discussed. We then demonstrate, first within the classical Einstein-Cartan-Dirac theory and second in the quantum heat kernel approach to the Dirac operator, how the Nieh-Yan form surfaces in both contexts, in contrast to what has been assumed previously.     

On the supersymmetric,non-abelian chiral anomalies

The anomaly is computed in a field theoretical model as an infinite power series in expV?1. After a redefinition of the current, the anomaly aquires a simpler form which is used for the verification of the consistency condition.     

On the polarization of chiral main-chain liquid-crystalline elastomers

A mechanism of developing a polarization in a chiral main-chain liquid-crystalline polymer by aligning the dipoles of the monomers is explored. It is shown that the polarization of a pure liquid crystal elastomer is zero in equilibrium due to rotation of the director in the elastomer. A constraint or specific non-ideality in the elastomer is required to prevent this relaxation of the director in order to realize a non-zero polarization. Three methods that circumvent this result are explored. We consider the effect of an oscillating shear, the pinning effect of the layers in a smectic-A composed of chiral smectogens and a binary mixture of chiral main chains and non-chiral side chains. Each of these methods is shown to produce a polarization, which is much larger than that produced in a piezoelectric -quartz crystal per unit stress.Received: 26 May 2004, Published online: 3 August 2004PACS: 61.30.Vx Polymer liquid crystals - 77.65.-j Piezoelectricity and electromechanical effects     

On the Hedgehog solution for the chiral bag

Using the cloudy-bag hamiltonian the nucleon is described by means of a variational quantum field theoretical approach (VQF) involving a coherent state of pions.. In the mean field approximation the well-known hedgehog baryon appears as a variational solution which minimizes the energy. Some properties of this solution are discussed, in particular in view of extracting good spin and isospin quantum numbers.     

On the boundary conditions as Dirac constraints

In this paper, the canonical quantization of singular Lagrangian defined in a finite volume is discussed by studying a 1 + 1 dimensional free Schrödinger field. We take the boundary conditions (BCs) as Dirac constraints, and show that those BCs as well as the intrinsic constraints (which are introduced by the singularities of Lagrangian) form the second class constraints. The quantization is performed canonically.Received: 30 August 2004, Revised: 2 October 2004, Published online: 17 December 2004PACS: 11.25-W, 04.60.D, 11.10.E     

On chiral realizations of confining theories

It is argued that chirality is not necessarily broken in SU(N) colour theories with a chiral flavour symmetry. In this case, massless fermion bound states contributr to anomaly equations, and loop expansions in a 1/N approach are invalid. As a hint to understanding which option is realized by the theory, we investigate it in two dimensions for very small quark masses. The light spectrum shows a rich structure not obtained in a $\text{1}\text{N}$ expansion. Light flavoured baryons and mesons indicate a partial realization of the chiral symmetry.