We study the equation of state and composition of hypernuclear matter within a relativistic density functional theory with density-dependent couplings. The parameter space of hyperon-scalar-meson couplings is explored by allowing for mixing and breaking of SU(6) symmetry, while keeping the nucleonic coupling constants fixed. The subset of equations of state, which corresponds to small values of hyperon-scalar-meson couplings, allows for massive M 2.25M compact stars; the radii of hypernuclear stars are within the range 12-14 km. We also study the equation of state of hot neutrino-rich and neutrinoless hypernuclear matter and confirm that neutrinos stiffen the equation of state and dramatically change the composition of matter by keeping the fractions of charged leptons nearly independent of the density prior to the onset of neutrino transparency. We provide piecewise polytropic fits to six representative equations of state of hypernuclear matter, which are suitable for applications in numerical astrophysics.

We present a simultaneous calculation of heavy single-Λ hypernuclei and compact stars containing hypernuclear core within a relativistic density functional theory based on a Lagrangian which includes the hyperon octet and lightest isoscalar-isovector mesons which couple to baryons with density-dependent couplings. The corresponding density functional allows for SU(6) symmetry breaking and mixing in the isoscalar sector, whereby the departures in the σ -Λ and σ -Σ couplings away from their values implied by the SU(3) symmetric model are used to adjust the theory to the laboratory and astronomical data. We fix σ -Λ coupling using the data on the single-Λ hypernuclei and derive an upper bound on the σ -Σ from the requirement that the lower bound on the maximum mass of a compact star is 2M .

Starting from equations of state of nucleonic and color-superconducting quark matter and assuming a first-order phase transition between these, we construct an equation of state of stellar matter, which contains three phases: a nucleonic phase, as well as twoflavor and three-flavor color-superconducting phases of quarks. Static sequences of the corresponding hybrid stars include massive members with masses of ∼2 M and radii in the range of 13 ≤ R ≤ 16 km. We investigate the integral parameters of rapidly rotating stars and obtain evolutionary sequences that correspond to constant rest-mass stars spinning down by electromagnetic and gravitational radiation. Physically new transitional sequences are revealed that are distinguished by a phase transition from nucleonic to color-superconducting matter for some configurations that are located between the static and Keplerian limits. The snapshots of internal structure of the star, displaying the growth or shrinkage of superconducting volume as the star's spin changes, are displayed for constant rest mass stars. We further obtain evolutionary sequences of rotating supramassive compact stars and construct pre-collapse models that can be used as initial data to simulate a collapse of color-superconducting hybrid stars to a black hole.

We investigate the modification of the pion self-energy at finite temperature due to its interaction with a low-density, isospin-symmetric nuclear medium embedded in a constant magnetic background. To one loop, for fixed temperature and density, we find that the pion effective mass increases with the magnetic field. For the $\pi^{-}$, interestingly, this happens solely due to the trivial Landau quantization shift $\sim |eB|$, since the real part of the self-energy is negative in this case. In a scenario in which other charged particle species are present and undergo an analogous trivial shift, the relevant behavior of the effective mass might be determined essentially by the real part of the self-energy. In this case, we find that the pion mass decreases by $\sim 10%$ for a magnetic field $|eB|\sim m_\pi^2$, which favors pion condensation at high density and low temperatures.Comment: 7 pages, 5 figure

We derive the hydrodynamical equations of r-mode oscillations in neutron stars in the presence of a novel damping mechanism related to particle number changing processes. The change in the number densities of the various species leads to new dissipative terms in the equations that are responsible for the rocket effect. We employ a two-fluid model, with one fluid consisting of the charged components, while the second fluid consists of superfluid neutrons. We consider two different kinds of r-mode oscillations, one associated with comoving displacements, and the second associated with countermoving, out of phase, displacements.