Neutron Stars 1: Equation of State and Structure

▪ Abstract We review theoretical developments in studies of dense matter and its phase structure of relevance to compact stars. Observational data on compact stars, which can constrain the properties of dense matter, are presented critically and interpreted.

https://www.annualreviews.org/doi/pdf/10.1146/annurev.nucl.56.080805.140600

Dense Matter in Compact Stars: Theoretical Developments and Observational Constraints

The first lecture provides an introduction to the physics of color superconductivity in cold dense quark matter. The main color superconducting phases are briefly described and their properties are listed. The second lecture covers recent developments in studies of color superconducting phases in neutral and β-equilibrated matter. The properties of gapless color superconducting phases are discussed.

Two Lectures on Color Superconductivity

Nonuniform structures of the nucleon matter at subnuclear densities are numerically studied by means of the density functional theory with relativistic mean fields coupled with the electric field. A particular role of the charge screening effects is demonstrated.

http://export.arxiv.org/pdf/nucl-th/0503027

Nuclear 'pasta' structures and the charge screening effect

Charge screening at first order phase transitions and hadron–quark mixed phase

We study the role of Coulomb and surface effects on the phase transition from dense nuclear matter to a mixed phase of nuclear and kaon-condensed matter. We calculate corrections to the bulk calculation of the equation of state (EOS) and the critical density for the transition by solving explicitly for spherical, cylindrical, and planar structures. The importance of Debye screening in the determination of the charged particle profiles is studied in some detail. We find that the surface and Coulomb contributions to the energy density are small, but that they play an important role in the determination of the critical pressure for the transition, as well as affecting the size and geometry of favored structures. This changes the EOS over a wide range of pressure and consequently increases the maximum mass by about 0.1 solar masses. Implications for transport properties of the mixed phase are also discussed.

https://arxiv.org/pdf/nucl-th/0010075.pdf

First Order Kaon Condensation in Neutron Stars: Finite Size Effects in the Mixed Phase

We study the transition from npe-type nuclear matter (consisting of neutrons, protons, and electrons) to matter containing strangeness, using a Walecka-type model predicting a first-order kaon-condensate phase transition. We examine the free energy of droplets of K matter as the density, temperature, and neutrino fraction are varied. Langer nucleation rate theory is then used to approximate the rate at which critical droplets of the new phase are produced by thermal fluctuations, thus giving an estimate of the time required for the new (mixed) phase to appear at various densities and various times in the cooling history of the protoneutron star. We also discuss the famous difficulty of ``simultaneous weak interactions'' which we connect to the literature on nontopological solitons. Finally, we discuss the implications of our results to several phenomenological issues involving neutron star phase transitions.

Travis Norsen

Papers

First Order Kaon Condensation in Neutron Stars: Finite Size Effects in the Mixed Phase

Strangeness nucleation in neutron star matter