Broiler walking ability and toe asymmetry under harsh rearing conditions

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

BFFT formalism applied to the minimal chiral Schwinger model

We consider the minimal chiral Schwinger model, by embedding the gauge non-invariant formulation into a gauge theory following the Batalin-Fradkin-Fradkina-Tyutin point of view. Within the BFFT procedure, the second-class constraints are converted into strongly involutive first-class ones, leading to an extended gauge-invariant formulation. We also show that, like the standard chiral model, in the minimal chiral model the Wess-Zumino action can be obtained by performing a q-number gauge transformation into the effective gauge non-invariant action.

Asymmetry parameter for nonmesonic hypernuclear decay

We give general expressions for the vector asymmetry in the angular distribution of protons in the nonmesonic weak decay of polarized hypernuclei. From these we derive an explicit expression for the calculation of the asymmetry parameter, a(Lambda), which is applicable to the specific cases of He-5(Lambda) and C-12(Lambda) described within the extreme shell model. In contrast to the approximate formula widely used in the literature, it includes the effects of three-body kinematics in the final states of the decay and correctly treats the contribution of transitions originating from single-proton states beyond the s-shell. This expression is then used for the corresponding numerical computation of a(Lambda) within several one-meson-exchange models. Besides the strictly local approximation usually adopted for the transition potential, we also consider the addition of the first-order nonlocality terms. We find values for a(Lambda) ranging from -0.62 to -0.24, in qualitative agreement with other theoretical estimates but in contradiction with some recent experimental determinations.

New possibilities for the gauging of chiral bosons

We study a new mechanism for the electromagnetic gauging of chiral bosons showing that new possibilities emerge for the interacting theory of chiral scalars. We introduce a chirally coupled gauge field necessary to mod out the degree of freedom that obstructs gauge invariance in a system of two opposite chiral bosons soldering them together.

AMBIGUITIES IN CHIRAL-SYMMETRY BREAKING USING THE EFFECTIVE POTENTIAL APPROACH

Using a form of the effective potential for composite operators with a variational approach we show that it is possible to get different directions of the chiral phase transition in QCD. Which one occurs depends on the way the Schwinger-Dyson equation for the fermion self-energy is used in the 2-loop term of the effective potential. We must choose the 2-loop term which agrees with phenomenology in each form of the effective potential.

CHIRAL BACKGROUND FOR THE 2-PION EXCHANGE NUCLEAR-POTENTIAL - A PARAMETRIZED VERSION

We argue that the minimal chiral background for the two-pion exchange nucleon-nucleon (NN) interaction has nowadays a rather firm conceptual basis, which entitles it to become a standard ingredient of any modern potential. In order to facilitate applications, we present a parametrized version of a configuration space potential derived previously. We than use it to assess the phenomenological contents of some existing NN potentials.

CHIRAL SCHWINGER MODEL WITH A PODOLSKY TERM AT FINITE-TEMPERATURE

We study an exactly solvable two-dimensional model which mimics the basic features of the standard model. This model combines chiral coupling with an infrared behavior which resembles low energy QCD. This is done by adding a Podolsky higher-order derivative term in the gauge field to the Lagrangian of the usual chiral Schwinger model. We adopt a finite temperature regularization procedure in order to calculate the non-trivial fermionic Jacobian and obtain the photon and fermion propagators, first at zero temperature and then at finite temperature in the imaginary and real time formalisms. Both singular and non-singular cases, corresponding to the choice of the regularization parameter, are treated. In the nonsingular case there is a tachyonic mode as usual in a higher order derivative theory, however in the singular case there is no tachyonic excitation in the spectrum.

A joint computational and experimental study of a novel dioxomolybdenum(VI) complex bearing chiral N,N-dimethyllactamide ligand

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)