We evaluate heavy-quark (HQ) transport properties in a Quark-Gluon Plasma (QGP) within a Brueckner many-body scheme employing interaction potentials extracted from thermal lattice QCD. The in-medium T -matrices for elastic charm-and bottom-quark scattering off light quarks in the QGP are dominated by attractive meson and diquark channels which support resonance states up to temperatures of ∼1.5 Tc. The resulting drag coefficient increases with decreasing temperature, contrary to expectations based on perturbative QCD scattering. Employing relativistic Langevin simulations we compute HQ spectra and elliptic flow in √ sNN =200 GeV Au-Au collisions. A good agreement with electron decay data supports our nonperturbative computation of HQ diffusion, indicative for a strongly coupled QGP. Experiments at the Relativistic Heavy-Ion Collider (RHIC) have shown that the matter produced in Au-Au collisions cannot be described by a weakly interacting gas of quarks and gluons, but rather consists of a strongly coupled Quark-Gluon Plasma (sQGP) with remarkably large opacity and low viscosity. The latter is required by hydrodynamic descriptions of the expanding fireball, implying rapid thermalization of the medium [1,2]. The understanding of these properties in terms of the underlying interactions in the QGP, as governed by Quantum Chromodynamics (QCD), is a key theoretical objective. A valuable probe of the sQGP are heavy quarks (charm and bottom) which, due to their large mass, m Q ≫T c (T c ≃180 MeV: critical temperature [3]), are believed to be sensitive to the processes that establish and maintain thermalization of the medium, even at soft momentum scales. RHIC data for single-electron (e ± ) spectra associated with semileptonic heavy-quark (HQ) decays in Au-Au collisions exhibit a surprisingly strong suppression and elliptic flow [4,5,6], indicating substantial collective behavior of charm quarks in the expanding fireball. Perturbative QCD (pQCD) calculations, based on radiative energy loss, cannot explain these findings, even after inclusion of elastic scattering [7,8]. Furthermore, it has been argued that the convergence of the perturbative series for the HQ diffusion constant is rather poor [9], which calls for nonperturbative approaches. Effective models with strong HQ coupling in the QGP [10,11,12,13] lead to significantly reduced thermal relaxation times compared to pQCD elastic scattering [14], resulting in better agreement [15,16] with e ± spectra [4,5,6].In the present article, we perform a microscopic calculation of HQ diffusion in the QGP employing a nonperturbative T -matrix approach [17] with a driving kernel (potential) estimated from finite-temperature lattice QCD computations. We include a complete set of color channels for heavy-light quark interactions, as well as l=0,1 partial waves together with HQ spin symmetry. This, in principle, provides an estimate of (elastic) transport coefficients without tunable parameters, albeit significant uncertainties remain in the definition of the potential. Within thes...

Inhomogeneous superconductors and inhomogeneous superfluids appear in a variety of contexts including quark matter at extreme densities, fermionic systems of cold atoms, type-II cuprates, and organic superconductors. In the present review the focus is on properties of quark matter at high baryonic density, which may exist in the interior of compact stars. The conditions realized in these stellar objects tend to disfavor standard symmetric BCS pairing and may favor an inhomogeneous color superconducting phase. The properties of inhomogeneous color superconductors are discussed in detail and in particular of crystalline color superconductors. The possible astrophysical signatures associated with the presence of crystalline color superconducting phases within the core of compact stars are also reviewed.Comment: Added 3 figures, added section II F, added section with conclusions. Several references added. Improved the quality of the presentation and removed various typos. Almost matches the version accepted for publication of Reviews of Modern Physic

This writeup is a compilation of the predictions for the forthcoming Heavy Ion Program at the Large Hadron Collider, as presented at the CERN Theory Institute ‘Heavy Ion Collisions at the LHC—Last Call for Predictions’, held from 14th May to 10th June 2007.

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We calculate the shear modulus of crystalline color superconducting quark matter, showing that this phase of dense, but not asymptotically dense, three-flavor quark matter responds to shear stress like a very rigid solid. To evaluate the shear modulus, we derive the low energy effective Lagrangian that describes the phonons that originate from the spontaneous breaking of translation invariance by the spatial modulation of the gap parameter ∆. These massless bosons describe space-and time-dependent fluctuations of the crystal structure and are analogous to the phonons in ordinary crystals. The coefficients of the spatial derivative terms of the phonon effective Lagrangian are related to the elastic moduli of the crystal; the coefficients that encode the linear response of the crystal to a shearing stress define the shear modulus. We analyze the two particular crystal structures which are energetically favored over a wide range of densities, in each case evaluating the phonon effective action and the shear modulus up to order ∆ 2 in a Ginzburg-Landau expansion, finding shear moduli which are 20 to 1000 times larger than those of neutron star crusts. The crystalline color superconducting phase has long been known to be a superfluid -by picking a phase its order parameter breaks the quark-number U (1)B symmetry spontaneously. Our results demonstrate that this superfluid phase of matter is at the same time a rigid solid. We close with a rough estimate of the pinning force on the rotational vortices which would be formed embedded within this rigid superfluid upon rotation. Our results raise the possibility that (some) pulsar glitches could originate within a quark matter core deep within a neutron star.