Narrow Results

We investigate the possibility of spatially inhomogeneous chiral and Cooper, or superconducting, pairing in the (1+1)-dimensional model by Chodos et al. [Phys. Rev. D61, 045011 (2000)] generalized to continuous chiral invariance. The consideration is performed at nonzero values of temperature T and quark number chemical potential μ. In the framework of the Fulde–Ferrel inhomogeneity ansatz for chiral and Cooper condensates, we show that if G₁>G₂, where G₁ and G₂ are the coupling constants in the quark–antiquark and diquark channels, then in the (μ, T)-phase diagram the superconducting phase is suppressed by spatially inhomogeneous chiral spiral phase with broken chiral symmetry. In contrast, in the above mentioned original Chodos et al. model, where only the opportunity for homogeneous condensates is taken into account, the superconducting phase is realized at sufficiently high values of μ at arbitrary values of G₂>0, including the interval 0<G₂<G₁.

Field models with $n$ extra spatial dimensions have a larger $SO(1,3+n)$ Lorentz symmetry which is broken down to the standard $SO(1,3)$ four-dimensional one by the compactification process. By considering Lorentz violating operators in a 5D supersymmetric Wess–Zumino model, which otherwise conserve the standard four-dimensional Poincaré invariance, we show that supersymmetry (SUSY) can be restored upon a simple deformation of the supersymmetric transformations. However, SUSY is not preserved in the effective 4D theory that arises after compactification when the 5D Lorentz violating operators do not preserve $Z_2:y\to -y$ bulk parity. Our mechanism unveils a possible connection among Lorentz violation and the Scherk–Schwarz mechanism. We also show that parity preserving models, on the other hand, do provide well defined supersymmetric KK models.

In the framework of an effective derivative-coupling model with scalar and vector mesons coupled to the octet of baryons and leptonic degrees of freedom, we have calculated in detail the nuclear property known as the compressibility function, using the mean-field theory formalism and taking into account chemical equilibrium, baryon number and electric charge conservation. The parameters of the model are chosen in order to reproduce phenomenology: an effective nucleon mass between 0.7–0.8 M_N and a compression modulus between 200–300 MeV.

We study the consequences of the presence of a negative electric charge condensate of antikaons in neutron stars using an effective model with derivative couplings. In our formalism, nucleons interact through the exchange of σ, ω and ϱ mesons, in the presence of electrons and muons, to accomplish electric charge neutrality and beta equilibrium. The phase transition to the antikaon condensate was implemented through the Gibbs conditions combined with the mean-field approximation, giving rise to a mixed phase of coexistence between nucleon matter and the antikaon condensate. Assuming neutrino-free matter, we observe a rapid decrease of the electron chemical potential produced by the gradual substitution of electrons by kaons to accomplish electric charge neutrality. The exotic composition of matter in neutron star including antikaon condensation and nucleons can yield a maximum mass of about M_ns ~ 1.76 M_⊙.

Properties of the ¹S₀ superfluid phase are studied for symmetric nuclear matter at finite temperature. It is described within a covariant hadronic field model, of the σ–ω type, with addition of density dependent correlations simulating effects due to finite extension of nucleons. The model is solved in a self-consistent Hartree–Bogoliubov approach, assuming instantaneous interactions in the superfluid phase. A comparison with the results obtained from several hadronic field models is made. Main characteristics of our description of the superfluid gap are in qualitative agreement with some studies using microscopic potentials, although further refinements could improve its performance.

Hadronic transitions are important decay modes of heavy quarkonia and serve as an elegant probe for the internal structure. Several remarkable discoveries have been made to identify the conventional heavy quarkonia and to extract useful information about the so called “XYZ” exotic states. We studied the hadronic transitions of higher charmonia in the framework of our recently proposed effective model to create light meson(s) in heavy quarkonium transitions. In this contribution, we discuss our results for the charmonium-$\eta$ decays of higher $S$ and $D$ wave vector charmonia. We also discuss quantum number ${(}^{2S+1}{L}_J)$ assignments for few experimentally observed charmoniumlike states.

In the study of nuclear matter it is common to employ effective models, that in essence are relativistic mean-field theories based on the Yukawa formulation. In such models we consider the baryons interacting through scalar and vector mesons exchanges, without taking into account the presence of quarks and gluons. The intensity of the effective interaction carried on by mesons is regulated by effective coupling constants which must be selected so that the theory is able to reproduce the basic properties of nuclear matter. The present investigation is a first approach on the analysis and explicitness of the effects of the hyperon-meson coupling constants on the prediction of measurable quantities. The purpose is to use an effective generalized derivative-coupling model and parametrize the equation of state (EoS) as a function of the coupling constants. We show the stiffness dependence of the EoS on the couplings and the related phenomenological results for the mass radius ratio of neutron stars. From observations one may constrain validity regions for the hyperon couplings.