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We study the spectrum of collective excitations in the inhomogeneous phases in the neutron star inner crust within a superfluid hydrodynamics approach. Our aim is to describe the whole range of wavelengths from the long-wavelength limit which can be described by macroscopic approaches and which is crucial for the low-energy part of the spectrum, to wavelengths of the order of the dimensions of the Wigner-Seitz cells, corresponding to the modes usually described in microscopic calculations. As an application, we will discuss the contribution of these collective modes to the specific heat of the "lasagna" phase in comparison with other known contributions. [ABSTRACT FROM AUTHOR]

In this work we present a newly constructed equation of state (EoS), applicable to stellar core collapse and neutron star mergers including the entire baryon octet. Our EoS is compatible with the main constraints from nuclear physics and, in particular, with a maximum mass for cold β-equilibrated neutron stars of 2M⊙ in agreement with recent observations. As an application of our new EoS, we compute numerical stationary models for rapidly (rigidly) rotating hot neutron stars. We consider maximum masses of hot stars, such as protoneutron stars or hypermassive neutron stars in the postmerger phase of binary neutron star coalescence. The universality of I-Q relations at nonzero temperature for fast rotating models, comparing a purely nuclear EoS with its counterparts containing Λ hyperons or the entire baryon octet, respectively, is discussed, too. We find that the I-Q universality is broken in our models when thermal effects become important, independent on the presence of entropy gradients. Thus, the use of I-Q relations for the analysis of protoneutron stars or merger remnant data, including gravitational wave signals from the last stages of binary neutron star mergers, should be regarded with care. [ABSTRACT FROM AUTHOR]

Using an axisymmetric numerical code, we perform an extensive study of the magnetic-field configurations in nonrotating neutron stars, varying the mass, magnetic-field strength and the equation of state. We find that the monopolar (spherically symmetric) part of the norm of the magnetic field can be described by a single profile, which we fit by a simple eighth-order polynomial, as a function of the star's radius. This new generic profile applies remarkably well to all magnetized neutron star configurations built on hadronic equations of state. We then apply this profile to build magnetized neutron stars in spherical symmetry, using a modified Tolman-Oppenheimer-Volkoff system of equations. This new formalism produces slightly better results in terms of mass-radius diagrams than previous attempts to add magnetic terms to these equations. However, we show that such approaches are less accurate than the usual, nonmagnetized TOV models, and that consistent models must depart from spherical symmetry. Thus, our "universal" magnetic-field profile is intended to serve as a tool for nuclear physicists to obtain estimates of the magnetic field inside neutron stars as a function of radial depth to deduce its influence on composition and related properties. It possesses the advantage of being based on magnetic-field distributions from realistic self-consistent computations which are solutions of Maxwell's equations. [ABSTRACT FROM AUTHOR]

The impact of electron-capture (EC) cross sections for neutron-rich nuclei on the dynamics of core collapse during infall and early post-bounce is studied by performing spherically symmetric simulations in general relativity using a multigroup scheme for neutrino transport and full nuclear distributions in extended nuclear statistical equilibrium models. We thereby vary the prescription for EC rates on individual nuclei, the nuclear interaction for the equation of state, the mass model for the nuclear statistical equilibrium distribution, and the progenitor model. In agreement with previous works, we show that the individual EC rates are the most important source of uncertainty in the simulations, while the other inputs only marginally influence the results. A recently proposed analytic formula to extrapolate microscopic results on stable nuclei for EC rates to the high densities and temperatures and the neutron-rich region, with a functional form motivated by nuclear-structure data and parameters fitted from large scale shell-model calculations, is shown to lead to a sizable (16%) reduction of the electron fraction at bounce compared to more primitive prescriptions for the rates, leading to smaller inner core masses and slower shock propagation. We show that the EC process involves -170 different nuclear species around 86Kr, mainly in the N=50 shell closure region, and establish a list of the most important nuclei to be studied in order to constrain the global rates. [ABSTRACT FROM AUTHOR]

We identify an observable imprint of a first-order hadron-quark phase transition at supranuclear densities on the gravitational-wave (GW) emission of neutron-star mergers. Specifically, we show that the dominant postmerger GW frequency fpeak may exhibit a significant deviation from an empirical relation between fpeak and the tidal deformability if a strong first-order phase transition leads to the formation of a gravitationally stable extended quark matter core in the postmerger remnant. A comparison of the GW signatures from a large, representative sample of microphysical, purely hadronic equations of state indicates that this imprint is only observed in those systems which undergo a strong first-order phase transition. Such a shift of the dominant postmerger GW frequency can be revealed by future GW observations, which would provide evidence for the existence of a strong first-order phase transition in the interior of neutron-stars. [ABSTRACT FROM AUTHOR]

The duration of the neutrino burst from the supernova event SN 1987A is known to be sensitive to exotic sources of cooling, such as axions radiated from the dense and hot hadronic matter thought to constitute the inner core of the supernova. We perform the first quantitative study of the role of hadronic matter beyond the first generation--in particular strange matter. We do so by consistently including the full baryon and meson octets, and computing axion emissivity induced from baryon-meson to baryon-axion scatterings as well as from baryon decays. We consider a range of supernova thermodynamic conditions, as well as equation-of-state models with different strangeness content. We obtain the first bound on the axial axion-strange-strange coupling, as well as the strongest existing bound on the axion-down-strange counterpart. Our bound on the latter coupling can be as small as O(10^{-2}) for f_{a}=10^{9}  GeV.

The analysis of color-superconducting two-flavor deconfined quark matter at moderate densities is extended to include a particular spin-1 Cooper pairing of those quarks which do not participate in the standard spin-0 diquark condensate. (i) The relativistic spin-1 gap delta(') implies spontaneous breakdown of rotation invariance manifested in the form of the quasifermion dispersion law. (ii) The critical temperature of the anisotropic component is approximately given by the relation T(')(c) approximately delta(')(T=0)/3. (iii) For massless fermions the gas of anisotropic Bogolyubov-Valatin quasiquarks becomes effectively gapless and two dimensional. Consequently, its specific heat depends quadratically on temperature. (iv) All collective Nambu-Goldstone excitations of the anisotropic phase have a linear dispersion law and the whole system remains a superfluid. (v) The system exhibits an electromagnetic Meissner effect.