No abstract available

[en] We have analyzed the equilibrium composition of quark matter consisting of approximately equal number of up, down and strange quarks, based upon the confinement mechanism of Fowler et al. (1981) and Pluemmer et al. (1984) in which the quark massed are considered density dependent. Using this model, we calculate the neutrino emissivity rate and the neutrino mean free path in quark matter and compare the results with Iwamoto (1982). We find that the emissivity rate is a slowly increasing function of the density, while the values of mean free path are slightly on the higher side than those of Iwamoto. (orig.)

No abstract available

[en] We have investigated the effect of temperature on strange quark matter by treating the quark-gluon interaction perturbatively to lowest order in the QCD coupling constant. We find that the quantities that depend on electron charge density get their leading contribution from the temperature dependent terms. In particular the quark charge density per baryon rises sharply with temperature and the neutrino emissivity increases by roughly two orders of magnitude when temperature dependent effects are taken into account. (orig.)

[en] Non-relativistically exact single scattering calculations for coherent pion photoproduction by deuterons at intermediate photon energies (200 MeV to 500 MeV) are presented. For the two-body γN → πN process, the well-known dispersion theoretic model by Chew et al is used and for the deuteron wave functions, the Yamaguchi and the two term Gaussian wave functions are employed. It is found that while both the wave functions reproduce the deuteron e.m. form factor reasonably well, the results for the pion photoproduction cross-section show, however, a sensitive dependence on their detailed forms. The angular distributions at various energies are found to have considerable variations from the usual impulse approximation calculations but tend to improve the agreement with the data in a large kinematical region. (author)

[en] The effect of strong magnetic field on the bulk properties of quark matter is reinvestigated taking u, d and s-quarks as well as electrons in the presence of magnetic field. Here the bag pressure is chosen such that in the absence of magnetic field and at zero temperature the binding energy of the uds-system is < 930 MeV while that of ud-system is greater than 940 MeV. It is observed that the equation of state changes significantly in a string magnetic field. At infinite temperature the electron chemical potential varies between 6 and 50 MeV. Thus the expansion of thermodynamical quantities in powers of T/(μ_i² - M_ν⁽ⁱ⁾²)^1/2 is valid only up to few MeV. For high temperatures ∼ 40 MeV the exact integral expressions are to be taken. (author)

[en] The possible phase transition to quark matter in a neutron star is considered using the neutron matter equation of state proposed recently by Canuto, Datta and Kalman (Phys. Lett.; B85:467 (1979)) which involves spin-2 meson interaction among nucleons. The corresponding equation of state for quark matter is taken from quantum chromodynamics. The Oppenheimer-Volkoff equation is then numerically solved to investigate the stability of a superdense system with quarkion cores. (author)

[en] The magnetisation of a non-interaction quark gas in an intense magnetic field has been calculated assuming that the quarks obey parastatistics of order three. It is observed that magnetisation would attain larger values if quarks could obey para-statistics of higher order. (author)

[en] Magnetic properties of a system of noninteracting relativistic quark gas in presence of an external intense magnetic field has been calculated assuming that quarks obey parastatistics of order three. It is found, although the magnetization is greater for quark gas than that for normal hadronic system, it is unlikely that the spontaneous magnetization will take place in a quark star. (orig.)

[en] The problem of existence of a family of quark stars has been investigated using the ground-state equations of state for the quark gas in second-order perturbation theory in quantum chromodynamics. (author)