High-density Neutron Matter Research Articles

Beyond BCS pairing in high-density neutron matter

Pairing gaps in neutron matter need to be computed in a wide range of densities to address open questions in neutron star phenomenology. Traditionally, the Bardeen-Cooper-Schrieffer approach has been used to compute gaps from bare nucleon-nucleon interactions. Here, we incorporate the influence of short- and long-range correlations into pairing properties. Short-range correlations are treated including the appropriate fragmentation of single-particle states, and they suppress the gaps substantially. Long-range correlations dress the pairing interaction via density and spin modes, and provide a relatively small correction. We use three different interactions as a starting point to control for any systematic effects. Results are relevant for neutron-star cooling scenarios, in particular in view of the recent observational data on Cassiopeia A.

Collective excitations of a quantized vortex in P23 superfluids in neutron stars

We discuss collective excitations (both fundamental and solitonic excitations) of quantized superfluid vortices in neutron $^3P_2$ superfluids, which likely exist in high density neutron matter such as neutron stars. Besides the well-known Kelvin modes (translational zero modes), we find a gapfull mode whose low-energy description takes the simple form of a double sine-Gordon model. The associated kink solution and its effects on spontaneous magnetization inside the vortex core are analyzed in detail.

Publisher's Note: Pairing in high-density neutron matter including short- and long-range correlations [Phys. Rev. C94, 025802 (2016)

Publisher's Note: Pairing in high-density neutron matter including short- and long-range correlations [Phys. Rev. C<b>94</b>, 025802 (2016)

Pairing in high-density neutron matter including short- and long-range correlations

Pairing gaps in neutron matter need to be computed in a wide range of densities to address open questions in neutron star phenomenology. Traditionally, the Bardeen-Cooper-Schrieffer approach has been used to compute gaps from bare nucleon-nucleon interactions. Here, we incorporate the influence of short- and long-range correlations in the pairing gaps. Short-range correlations are treated including the appropriate fragmentation of single-particle states, and substantially suppress the gaps. Long-range correlations dress the pairing interaction via density and spin modes, and provide a relatively small correction. We use different interactions, some with three-body forces, as a starting point to control for any systematic effects. Results are relevant for neutron-star cooling scenarios, in particular in view of the recent observational data on Cassiopeia A.

Magnetic properties of quantized vortices in neutronP23superfluids in neutron stars

We discuss quantized vortices in neutron $^3P_2$ superfluids, which are believed to realize in high density neutron matter such as neutron stars. By using the Ginzburg-Landau free energy for $^3P_2$ superfluids, we determine the ground state in the absence and presence of the external magnetic field, and numerically construct $^3P_2$ quantized vortices in the absence and presence of the external magnetic field along the vortex axis (poloidal) or angular direction (toroidal). We find in certain situations the spontaneous magnetization of the vortex core, whose typical magnitude is about $10^{7-8}$ Gauss, but the net magnetic field in a neutron star is negligible because of the ratio of the vortex core size $\sim 10$fm and the intervortex distance $\sim 10^{-6}$m in a vortex lattice.

3PF2pairing in high-density neutron matter

The onset of the superfluid phase in high-density neutron matter is studied within the BCS framework with two- and three-body forces. When including the strong correlation effects in the gap equation, the pairing gap turns out to be nonvanishing in a range of densities about $0.1--0.4\phantom{\rule{0.28em}{0ex}}{\text{fm}}^{\ensuremath{-}3}$ with a peak value a bit less than 0.05 MeV. These results could limit the role of the ${}^{3}{\mathit{PF}}_{2}$ superfluidity in the interpretation of phenomena occurring in the neutron-star core.

The impact of charge symmetry and charge independence breaking on the properties of neutrons and protons in isospin-asymmetric nuclear matter

We investigate the effects of charge independence and charge symmetry breaking in neutron-rich matter. We consider neutron and proton properties in isospin-asymmetric matter at normal densities as well as the high-density neutron matter equation of state and the bulk properties of neutron stars. We find charge symmetry and charge independence breaking effects to be very small.

Nucleation of Quark Matter in Neutron Star Cores

We consider the general conditions of quark droplet formation in high-density neutron matter. The growth of the quark bubble (assumed to contain a sufficiently large number of particles) can be described by means of a Fokker-Planck equation. The dynamics of the nucleation essentially depends on the physical properties of the medium in which it takes place. The conditions for quark bubble formation are analyzed within the framework of both dissipative and nondissipative (with zero bulk and shear viscosity coefficients) approaches. The conversion time of the neutron star to a quark star is obtained as a function of the equation of state of the neutron matter and of the microscopic parameters of the quark nuclei. As an application of the formalism obtained, we analyze the first-order phase transition from neutron matter to quark matter in rapidly rotating neutron star cores, triggered by the gravitational energy released during the spinning down of the neutron star. The endothermic conversion process, via gravitational energy absorption, could take place in a very short time interval, of the order of a few tens of seconds, in a class of dense compact objects with very high magnetic fields, called magnetars.

New Skyrme effective forces for supernovae and neutron rich nuclei

New Skyrme-like effective interactions are proposed suitable for neutron stars, supernovae and neutron-rich nuclei. The parameters of the force are adjusted to the properties of the symmetric infinite nuclear matter, with an additional constraint on the low and high density neutron matter equation of state. Preliminary Hartree-Fock plus BCS calculations along series of isotopes are shown. They seem to solve the problem of large discrepancies observed with other parametrizations.

On the Existence of Combined Condensation of Neutral and Charged Pions in Neutron Matter

Combined condensation of neutral and charged pions at high-density neutron matter is studied in an approach based on the chiral symmetry. Energy density in the combined ;ro-;rc condensed phase to be considered as most energetically favored is derived in a realistic calculation, where we take into account the isobar L1 (1232) degrees of freedom, baryon-baryon short-range correlations described in terms of the Landau-Migdal parameter g', and form factors in the ;r-baryon vertex. Characteristic features of this phase are discussed in comparison with those of the pure ;ro or the pure ;rC condensa­ tion .. The combined ;ro_;rc condensed phase sets in at baryon density (3~5) times the nuclear density po depending on g' after the appearance of the pure ;rc condensed phase.

Variational treatment of a π0-condensed state of high-density neutron matter

The stability of the standard ground state of pure neutron matter against a nonuniform spin-ordered state, yielding a nonvanishing expectation value of the π 0 field, has been studied within the framework of the Jastrow variational approach. The results indicate that a first-order transition to the π 0 condensate occurs at a density larger than normal nuclear density by a factor 3–4, provided a Δ-mixing of about 10% is included into the neutron states.

Rotating neutron star structure - Implications of the millisecond pulsar PSR 1937 + 214

view Abstract Citations (22) References (39) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Rotating neutron star structure : implications of the millisecond pulsar PSR 1937 +214. Ray, A. ; Datta, B. Abstract Rapidly rotating fluid objects of a given mass can remain stable only up to a critical angular speed, beyond which they may undergo instabilities leading to disruption. A semi-Newtonian condition of rotational stability applied to the recently discovered millisecond pulsar PSR 1937 + 214 implies lower bounds on the mass and moment of inertia and an upper bound on the radius of the neutron star. These upper and lower bounds are dependent on the equation of state of high-density neutron matter. Critically rotating realistic neutron star models are constructed using the prescription of Hartle and Thorne (1968), for six representative equations of state. The lower bounds on mass are found to be substantially higher than previous estimates. Results for various equations of state of neutron matter at high densities are compared with observational data for neutron star masses. Publication: The Astrophysical Journal Pub Date: July 1984 DOI: 10.1086/162233 Bibcode: 1984ApJ...282..542R Keywords: Neutron Stars; Pulsars; Stellar Models; Stellar Rotation; Stellar Structure; Angular Velocity; Differential Equations; Equations Of State; Rotating Matter; Astrophysics full text sources ADS | data products SIMBAD (1)

On the existence of a nonuniform spin-isospin ordered phase in high-density neutron matter

Using a Jastrow-like correlated wavefunction and a realistic two-body interaction, the energy per particle of neutron matter has been evaluated both in the normal uniform phase and in a π 0-condensed phase exhibiting one-dimensional density fluctuations and spin-isospin order. The numerical results indicate that the standard configuration is energetically favored, even at very high densities.