Physics of Neutron Star Crusts

Abstract

The physics of neutron star crusts is vast, involving many different research fields, from nuclear and condensed matter physics to general relativity. This review summarizes the progress, which has been achieved over the last few years, in modeling neutron star crusts, both at the microscopic and macroscopic levels. The confrontation of these theoretical models with observations is also briefly discussed.

Gravitational radiation from crystalline color-superconducting hybrid stars

“…6 displays maximal quadrupole moments of a sequences of hybrid stars derived by combining Eqs. ( 4), ( 5) and (6). The quadrupole moment depends on the product of the breaking strain and the shear modulus.…”

“…The maximal quadrupole moment scales as Q max ∼ σmax ∆ 2 according to Eqs. ( 4)- (6). 7), where the masses and radii are set equal to that of the quark cores of microscopic models (the values of the central density on the x axis do not represent the central densities of these models).…”

“…Rotating, isolated compact stars will emit gravitational radiation if their mass distribution is nonaxisymmetric with respect to their rotation axis. The axial symmetry can be broken over detectable time-scales in a number of ways, e. g., through distortions in the solid phases of the star [1,2,3,4,5,6,7], deformations caused by strong magnetic fields [8,9,10,11,12], or by precession [13,14,15,16,17]. Continuous gravitational waves emitted by nonaxisymmetric rotating compact stars are expected to be in the bandwidth of current gravitational wave interferometric detectors.…”

Stellar structure equations in extended Palatini gravity

“…Despite these difficulties, the study of the effects of alternative equations on the structure of compact objects, stellar formation and evolution, and peculiar objects (instability strips, protostars, etc) has attracted some attention in the context of modified theories of gravity of different types [8][9][10][11]. Given the increasingly high accuracy and resolution of currently available observational techniques (see for instance [12,13]) and the discovery of rare objects which defy the standard model of stellar formation and evolution [14], the study of stellar properties and new solutions in extensions of GR could provide new insights to interpret observations and offer new avenues to test the strong field regime of gravitation and, therefore, help determine or set limits to potential corrections to Einstein's equations.…”

Bragg diffraction and the iron crust of cold neutron stars

“…Current theories of Neutron Stars (Bombaci 2007) imply that as pressure builds up towards the interior of the star there are successive phase transitions from an iron crust (Chamel & Haensel 2008;de Young 1991), to a nuclear medium with high neutron density, to a neutron Fermi liquid, to more exotic forms of matter. It has proven difficult to make empirical progress on the star's composition.…”