Title: Structure of Neutron/Quark stars and constraints from observation
Abstract: Although the equation of state of nuclear matter (possibly mixed with quark matter) is unknown at high densities, nucleon scattering and nuclear structure constrains it around normal nuclear matter densities and causality at higher densities. Calculated masses, radii and cooling seem to agree with recent observations from LMXB QPO's and burster oscillations, and our nearest nearest neutron star. Superconductivity is notoriously difficult to calculate in the strongly interacting and correlated nuclear and quark liquids. New insight may come from trapped fermionic atomic systems.
Title: Diquark properties and the TOV equations
Abstract: We present various results from including diquark properties and the gap equations into the TOV equations for compact quark objects. One such property is the diquark form factor, which has a strong influence on various quantities. We discuss the consequences for quark stars.
Title: Strange star candidates in low mass X-ray binaries
Abstract: Strange stars (SS) are hypothetical compact stars which are entirely made of deconfined u,d,s quark matter (strange quark matter). Using recent observational data collected by the Beppo-SAX satellite and by the Rossi X-ray Timing Explorer (RXTE), we extract a firm upper limit for the radius of the compact stars in the newly discovered millisecond X-ray pulsar SAX J1808.4-3658 (ref.[1]), and in the atoll source 4U 1728-34 (ref.[2]). Comparing the mass-radius relation of SAX J1808.4-3658 and of 4U 1728-34 with theoretical models for both neutron stars and strange stars, we argue that the compact objects in these two X-ray sources are likely strange star candidates. [1] X.-D. Li, I. Bombaci, M. Dey, J. Dey, and E.P.J. van den Heuvel, Phys. Rev. Lett. 83, (1999), 3776. [2] X.-D. Li, S. Ray, J. Dey, M. Dey, and I. Bombaci, Astrophys. Journal. 527, (1999), L51.
Title: Diquarks degrees of freedom in the EOS and the compactness of compact stars
Abstract: We study the effects of diquarks on the EOS using a version of the density-dependent mass model. After discussing the general features (including possible self-bound states) we compare the EOS with existing models and quantify its influence on cold, static stellar models. We revisit the astrophysical determination of masses and radii with emphasis on Her-X1 and relate them to the diquark degrees of freedom.
Title: Stars with a Supersymetric Baryon - an Alternative to Quark Stars?
Abstract: A light, stable, spin zero, supersymmetric baryon is a possible candidate for dark matter. If such particles exist, they could appear in neutron stars with hyperon formation serving as an intermediate stage, and could also condense into a compact object of their own, a \"supersymmertic star\". It is shown that properties of neutron stars with the supersymmetric baryon are consistent with observations, and that \"supersymmetric stars\" could, under some circumsatnces, mimic the properties of quark stars. Implications for cooling processes will be discussed as well.
Title: From Neutron Stars to Quark Stars
Abstract: In my talk, I will review a number of observational features by means of which the possible existence of quark matter in neutron stars could register itself. I will begin with a recent study, where we modeled the spin evolution of X-ray neutron stars in binary systems, which are being spun up by mass transfer from accretion disks. Our study revealed that quark deconfinement, induced by the changing spin of such neutron stars, can lead to a pronounced plateau in the spin frequencies of such stars. This finding provides a possible explanation for the anomalous spin frequency distribution of neutron stars in low-mass X-ray binaries, observed with the Rossy X-Ray Timing Explorer, which all lie in a rather narrow band. Further points of my talk concern a stellar backbending predicted for isolated neutron stars that built up quark matter cores in their centers because of steady compression, and the existence of entirely new classes of compact stars - ranging from compact strange stars to strange dwarfs - which should exist if strange quark matter is more stable than nuclear matter.
Title: Tensor Correlations and Pions in Dense Matter
Abstract: The study of tensor correlations and pions in dense matter in astronomical contexts has recently acquired renewed importance for a number of reasons. One is the discovery by Akmal, Pandharipande and Ravenhall (Phys. Rev. C56 2261 (1997), Phys.Rev. C58, 1804 (1998)) of a striking increase in tensor correlations in cold matter at densities not far above that of isospin-symmetric nuclear matter at saturation. A second is that the only "successful" simulation of stellar collapse is that of Mayle and Wilson, in which softening of the equation of state by the appearance of thermal pions played an important role. A third is that the strength of tensor correlations is a crucial ingredient in calculating rates of neutrino emission and scattering, which are needed in calculations of stellar collapse and of the cooling of neutron stars. I shall describe some recent results for the response of nuclear matter, and indicate issues that are as yet unresolved.
Title: The observational appearance of strange stars
Abstract: Strange quark matter with a density of $\\\\sim 5\\\\times 10^{14}$ g~cm$^{-3}$ might exist up to the surface of a strange star. Such a surface would differ qualitatively from that of a neutron star. This opens observational possibilities to distinguish strange stars from neutron stars. The thermal emission of photons and $e^+e^-$ pairs from the bare (or nearly bare) quark surface of a hot strange star is reviewed. Some criteria are suggested for deciding whether a compact object can be a strange-star candidate. Known compact objects which answer these criteria and may be strange stars are discussed. Soft gamma-ray repeaters are among these objects. The bursting activity of a soft gamma-ray repeater may be explained by fast heating of the bare quark surface of a strange star up to the temperature of $\\\\sim (1-2)\\\\times 10^9$~K and its subsequent thermal emission. The light curves of the two giant flares observed from SGR 0526-66 and SGR 1900+14 are fitted. Observational tests to verify the strange-star model for soft gamma-ray repeaters are suggested.If this model is valid, Witten\\\'s conjecture that strange quark matter is stable at zero pressure will be confirmed. Besides, it will be possible to restrict significantly the region of strange stars at the QCD phase diagram
Title: Structure of rapidly rotating strange stars:salient differences with neutr.stars
Abstract: We compute structures of rapidly rotating strange stars, considering the full effect of general relativity. The parameters computed are gravitational mass (M), equatorial radius (R), angular momentum (J), the radius ($r_{\\\\rm orb}$) of the innermost stable circular orbit (ISCO). Beyond a certain critical value of J, we observe the $r_{\\\\rm orb}$ to increase with J (a property seen neither in rotating black holes nor in rotating neutron stars). The reason for this is traced to the crucial dependence of $dr_{\\\\rm orb}/dJ$ on the rate of change of the radial gradient of the Keplerian angular velocity at $r_{\\\\rm orb}$ with respect to $J$. The structure parameters so obtained are compared with those of neutron stars, as an attempt to provide signatures for distinguishing between the two. We show that when the full gamut of strange star equation of state models, with
Title: QCD Phase Diagram and Explosive Astrophysics
Abstract: I first review the QCD phase diagram, with emphasis on recent advances in color superconductivity. I note the existence of first order phase boundaries as a function of baryon density associated with chiral symmetry restoration as well as color superconductivity. Although the critical densities for these transitions are unknown, they are likely to occur at a few to ten times nuclear density. Such densities are plausibly achieved at core bounce in a type II supernova, as well as in mergers of neutron star binaries. The latent energy liberated can be of order a few percent of the rest mass of the region which undergoes the transition, and is of the right size to power type II supernovae or possibly hypernovae.
Title: Crystalline color superconductivity in dense matte
Abstract: We analyze the Schwinger-Dyson equations for quark two-pont function to find out when the LOFF state is energetically favorable. We briefly discuss the application of the crystalline color superconductivit to compact stars.
Title: Effective theories for QCD at high density
Abstract: I will discuss effective lagiangians describing QCD at high density. In particular I will consider the Color Flavor Locking (CFL) phase for $N_f=3$ presenting also the calculation at weak couplings of various parameters entering into the definition of the effective lagrangian. I will present also the case $N_f=2$ and the possibility of a crystalline phase (LOFF) originating for a particular set of values of the difference between the values of the chemical potentials for up and down quarks.
Title: EFFECTIVE FIELD THEORY FOR THE CRYSTALLINE COLOR SUPERCONDUCTIVE PHASE OF QCD
Abstract: I will present an effective field theory for high density, low temperature QCD in the crystalline colour superconductive phase (LOFF phase). This interesting phase of QCD is characterized by a gap parameter with a crystalline pattern, breaking traslational and rotational invariance, and could have astrophysical applications. In the effective theory the fermions have a Majorana mass, which, besides colour, breaks translation and rotation symmetries. Integrating out the fermions leads eventually to an effective lagrangian in terms of the phonon field only, which satisfies an anisotropic dispersion relation.
Title: Color superconducting quark matter in compact stars
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Title: Color Superconductivity and Blinking Proto-Neutron Stars
Abstract: If quark matter exists in the cores of neutron stars, it is most likely color superconducting. Thus a phase transition from free to paired quark matter might occur during the first minute of proto-neutron star evolution. Critical behavior of the medium will modify neutrino diffusion, possibly leading to a short pause in the neutrino signal detected on Earth.
Title: Color-flavor locking in strange stars, strangelets, and cosmic rays
Abstract: I expect to review a couple of recent developments and some ongoing work related to 1) R-mode instabilities in color-flavor locked strange stars 2) Properties of color-flavor locked strangelets 3) Prospects for observations of quark matter in cosmic rays
Title: Confinement and domain walls in high density quark matter
Abstract: Two features of high density quark matter -- the possible confinement with a very small energy scale and the existence of non-topological domain walls -- are described.
Title: Introduction to effective Lagrangians for QCD
Abstract: A hopefully pedagogic introduction to attempts at an effective Lagrangian (in the sense of using fields representing physical particles rather then quarks and gluons) treatment of QCD will be given. The historical evolution of the subject will be discussed. Some remarks related to a recent model of GRBs will be made. Finally, some recent work on low energy strong interactions will be briefly described.
Title: Low Energy Effective Lagrangian for 2 flavor Color Superconductivity
Abstract: I review the symmetries of color superconductivity and the relation with global anomaly constraints. I will then construct the low energy effective Lagrangian for two light flavor Color Superconductivity (2SC). I will also show how to build the effective Lagrangian for the Glueball sector of 2SC.
In this session speakers will be asked questions by the students. The topics (from the conference) and related questions will be selected by the students themselves.
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Title: Prompt Emission and Early Afterglows of GRBs
Abstract: Observations of GRBs and their emission mechanisms will be reviewed. Internal shocks in the fireball and the blast wave formation will be discussed.
Title: GRB-Compact Star connection ?
Abstract: I will discuss models attempting to link GRBs to compact objects. In particular those involving intrinsic properties of quark stars.