Nonlocality effects in the phase diagram of neutral quark matter

We construct phase diagrams of two-flavor quark matter under compact star constraints for two nonlocal, covariant quark models (instanton liquid and one-gluon exchange (OGE) inspired) within the mean field approximation and compare the results for different diquark coupling strengths. For the OGE model, stable hybrid stars with quark cores are obtained. The text was submitted by the authors in English.     

Charged and superconducting vortices in dense quark matter

Quark matter at astrophysical densities may contain stable vortices due to the spontaneous breaking of hypercharge symmetry by kaon condensation. We argue that these vortices could be both charged and electrically superconducting. Current carrying loops (vortons) could be long-lived and play a role in the magnetic and transport properties of this matter. We provide a scenario for vorton formation in protoneutron stars.     

Instability of quark matter core in a compact newborn neutron star with moderately strong magnetic field

It is explicitly shown that if phase transition occurs at the core of a newborn neutron star with moderately strong magnetic field strength, which populates only the electron’s Landau levels, then in the β -equilibrium condition, the quark core is energetically much more unstable than the neutron matter of identical physical condition.     

The colour superconducting phase transition in quark matter

The free energy functional for colour superconducting quark matter is constructed including the radiative corrections due to gluon fields in one-loop approximation. The jump in the order parameter and the latent heat at the phase transition are discussed.     

Possible color instabilities in abnormal quark matter

When the spatial wave function of a multiquark system is completely antisymmetric, the color-magnetic interaction energy may become attractive or may vanish. Under certain circumstances, this may cause a color-magnetic or color-electric collapse in the abnormal quark matter of singly occupied single-particle orbital states.     

Neutrinos in dense quark matter and cooling of compact stars

We discuss that observational constraints on neutrino cooling processes may restrict the spectrum of quark matter phases admissible for compact star interiors.     

Static quark anti-quark free and internal energy in two-flavor QCD

We study the change in free and internal energy due to the presence of a heavy quark anti-quark pair in a thermal heat bath in QCD with two flavors of staggered quarks at finite temperature. We discuss string breaking below as well as screening above the transition. Similarities and differences to the quenched case are discussed.Arrival of the final proofs: 24 March 2005PACS: 11.15.Ha, 11.10.Wx, 12.38.Mh, 25.75.Nq     

Phase diagram of neutron star quark matter in nonlocal chiral models

We analyze the phase diagram of two-flavor quark matter under neutron star constraints for a nonlocal covariant quark model within the mean-field approximation. Applications to cold compact stars are discussed.     

Vacuum fluctuation effects on hyperonic neutron star matter

The vacuum fluctuation （VF） effects on the properties of the hyperonic neutron star matter are investigated in the framework of the relativistic mean field （RMF） theory. The VF corrections result in the density dependence of in-medium baryon and meson masses. We compare our results obtained by adopting three kinds of meson-hyperon couplings. The introduction of both hyperons and VF corrections softens the equation of state （EoS） for the hyperonic neutron star matter and hence reduces hyperonic neutron star masses. The presence of the δ field enlarges the masses and radii of hyperonic neutron stars. Taking into account the uncertainty of meson-hyperon couplings, the obtained maximum masses of hyperonic neutron stars are in the range of 1.33M⊙-1.55M⊙.     

Topology change and emergent scale symmetry in compact star matter via gravitational wave detection

Topological structure has been extensively studied and confirmed in highly correlated condensed matter physics. We explore the gravitational waves emitted from binary neutron star mergers using the pseudoconformal model for dense nuclear matter for compact stars. This model considers the topology change and the possible emergent scale symmetry and satisfies all the constraints from astrophysics. We find that the location of the topology change affects gravitational waves dramatically owing to its effect on the equation of state. In addition, the effect of this location on the waveforms of the gravitational waves is within the ability of the on-going and up-coming facilities for detecting gravitational waves, thus suggesting a possible way to measure the topology structure in nuclear physics.     

Conversion of nuclear to 2-flavour quark matter in rotating compact stars: A general relativistic perspective

The conversion of neutron star to strange star is argued to be a two step process. The first process involves the deconfinement of nuclear to two-flavour quark matter. The GR results shows that the propagating front breaks up into fragments which propagate with different velocities along different directions. The time taken for this conversion to happen is of the order of few ms. This calculation indicates the inadequacy of non-relativistic (NR) or even Special Relativistic (SR) treatments for these cases.     

Jahn-Teller electron-lattice interaction and interband pairing in superconducting oxides

The possibility of interband pairing of electrons via Jahn-Teller electron-lattice interaction in superconducting oxides is investigated. The calculation of electron-lattice coupling energy shows the opposite signs of electron-phonon interaction for two non-bonding subbands which are originated from thep orbits of the O₂ atoms in LaBaCuO system and the O₁ and O₄ atoms in YBaCuO system. This interaction leads to the intersubband pairing which affects almost the whole Fermi sphere of the subbands except a thin shell near Fermi surface. The restriction onT _c due to the small Debye frequency in BCS theory is then released and highT _c can be reached even in weak coupling case. Several properties of these materials are calculated in this model and the relation to experimental data is discussed.     

Spin fluctuations and unconventional superconducting pairing in iron-based superconductors

In this article, we review the recent theoretical works on the spin fluctuations and superconductivity in iron-based superconductors. Using the fluctuation exchange approximation and multi-orbital tight-binding models, we study the char- acteristics of the spin fluctuations and the symmetries of the superconducting gaps for different iron-based superconductors. We explore the systems with both electron-like and hole-like Fermi surfaces （FS） and the systems with only the electron-like FS. We argue that the spin-fluctuation theories are successful in explaining at least the essential part of the problems, indicating that the spin fluctuation is the common origin of superconductivity in iron-based superconductors.