119116866
Phase diagram of chiral quark matter: Fulde-Ferrell pairing from weak to strong coupling
We calculate the phase diagram of two-flavor quark matter in the temperature-flavor asymmetry plane in the case where there are three competing phases: the homogeneous Bardeen-CooperSchrieffer (BCS) phase, the unpaired phase, and a phase with broken spatial symmetry, which is here taken to be the counterpart of the Fulde-Ferrell (FF) phase in condensed matter physics. The system belongs to the universality class of paramagnetic-ferromagnetic-helical systems, and therefore contains a tricritical Lifshitz point in its phase diagram, where the momentum scale characterizing the breaking of translational invariance has a critical exponent of 1/2 to leading order. We vary the coupling constant of the theory, which is obtained from integrating out the gluonic degrees of freedom. In weak coupling, the FF phase is favored at arbitrary flavor asymmetries for sufficiently low temperatures; at intermediate coupling its occupancy domain is shifted towards larger asymmetries. Strong coupling features a new regime of an inhomogeneous FF state, which we identify with a current-carrying Bose-Einstein condensate of tightly bound up and down quarks. The temperature and asymmetry dependence of the gap function is studied. It is shown that the anomalous temperature dependence of the gap in the homogeneous, flavor-asymmetric phase is transformed into a normal dependence (self-similar to the BCS phase) at arbitrary coupling, once the FF phase is allowed for. We analyze the occupation numbers and the Cooper-pair wave function and show that when the condensate momentum is orthogonal to the particle momentum the minority component contains a blocking region (breach) around the Fermi sphere in the weak-coupling limit, which engulfs more low-momentum modes as the coupling is increased, and eventually leads to a topological change in strong coupling, where the minority Fermi sphere contains either two occupied strips or an empty sphere. For non-orthogonal momenta, the blocking region is either reduced or extinct, i.e., no topological changes are observed.
16685281
Neutron-Phonon Interaction in Neutron Star Crusts
The phonon spectrum of Coulomb lattice in neutron star crusts above the neutron drip density is affected by the interaction with the ambient neutron Fermi-liquid. For the values of the neutron-phonon coupling constant in the range $0.1 \le \lambda \le 1$ an appreciable renormalization of the phonon spectrum occurs which can lead to a lattice instability manifested in an exponential growth of the density fluctuations. The BCS phonon exchange mechanism of superconductivity leads to neutron pairing with a gap in the neutron excitation spectrum comparable to that due to the direct nuclear interaction.
10967331
Spin Evolution of Pulsars with Weakly Coupled Superfluid Interiors
We discuss the spin evolution of pulsars in the case where a superfluid component of the star is coupled to the observable crust on long, spin-down timescales. The momentum transfer from the superfluid interior results in an apparent decay of the external torque and, after a dramatic increase, in an asymptotic decrease of the generic value of the braking index, e.g., n = 3, to values n ~ 2.5 if the magnetic field of the star does not decay over its lifetime. In the case where an exponential decay of the magnetic field toward a residual value occurs, the star undergoes a spin-up phase after which it could emerge in the millisecond sector of the P- diagram.
118545262
Phase diagram of chiral quark matter: Color and electrically neutral Fulde-Ferrell phase
The phase diagram of charge and color neutral two-flavor color superconducting quark matter is studied including the homogeneous two-flavor superconductor (2SC) and the inhomogeneous Fulde-Ferrell (FF) phases within the Nambu-Jona-Lasinio model. The low-temperature domain T{<=}5 MeV of the phase diagram contains the FF phase, which borders at high temperatures to the 2SC phase. The critical temperature of phase transition from the 2SC to the unpaired state is in the range 20-30 MeV. We derive the equation of state of matter and its composition and show that matter in mature compact stars should be in the inhomogeneous FF-like superconducting state. We briefly discuss the astrophysical implications of such a phase in compact stars.
123150107
Low-temperature transport coefficients of nuclear matter with in-medium modifications
Abstract Transport coefficients of dense symmetrical nuclear matter in the low-temperature regime are calculated taking into account the modifications of the quasi-particle scattering amplitudes in the nuclear environment. The two-body scattering T -matrix, the in-medium nucleon-nucleon cross section, and the critical temperature for the superfluid phase transition for the different partial wave channels are evaluated using a separable form of the nucleon-nucleon interaction. As a precursor effect of the onset of superfluid phase, the transport coefficients show non-trivial rediction with the decreasing temperature. The in-medium transport coefficients are found to be considerably modified compared with the results obtained with either the free scattering cross section or the isotropic residual value σ ∼ 40 mb.
7071448
Neutrino-pair emission in a strong magnetic field
We study the neutrino emissivity of strongly magne- tized neutron stars due to the charged and neutral current cou- plings of neutrinos to baryons in strong magnetic fields. The leading order neutral current process is the one-body neutrino- pair bremsstrahlung, which does not have an analogue in the zero field limit. The leading order charged current reaction is the known generalization of the direct Urca processes to strong magnetic fields. While for superstrong magnetic fields in excess of 10 18 G the direct Urca process dominates the one-body bremsstrahlung, we find that for fields on the order 10 16 10 17 G and temperatures a few times10 9 K the one-body bremsstrahlung is the dominant process. Numerical computa- tion of the resulting emissivity, based on a simple parametriza- tion of the equation of state of the npe-matter in a strong mag- netic field, shows that the emissivity of this reaction is of the same order of magnitude as that of the modified Urca process in the zero field limit.
118895506
From integrable models to gauge theories : a volume in honor of Sergei Matinyan
3D Ising model on dual BCC lattice - the sign-factor, J. Ambjorn et al on algebra of the Baxter Q-operators, A.A. Belavin and R.A. Usmanov aspect of locality in the form factor programme, O.A. Castro-Alvaredo and A. Fring on the origin of symmetries, J.L. Chkareuli generalization of magnetic fields in cosmology, A.D. Dolgov the coefficients of the Seiberg-Witten prepotential as interaction numbers, R. Flume et al on the cosmological constant and vacuum energy, V.G. Gurzadyan and S.S. Xue topics in Parton model, O.V. Kancheli Bjorken asymptotics of QCD and integrable systems, D. Karakhanyan and R. Kirschner entropy and area of black holes in loop quantum gravity, I.B. Khriplovich statistical ensembles and density of states, V. Kostrykin and R. Schrader the anthropic principle revisited, B. Mueller fundamental units, L.B. Okun structure constant of boundary operators in Liouville field theory, B. Ponsot and J. Teschner winding number versus Chern-Pontryagin charge, T. Tchrakian magnetically induced vacuum-energy releasing, S.S. Xue. (Part contents)