scholarly journals A CBF calculation of 1S0 Superfluidity in the Inner Crust of Neutron Stars

2019 ◽  
Vol 17 ◽  
pp. 23
Author(s):  
G. Pavlou ◽  
E. Mavrommatis ◽  
Ch. C. Moustakidis ◽  
J. W. Clark
Keyword(s):  
Equation Of State ◽  
Neutron Stars ◽  
Basis Function ◽  
Correlation Functions ◽  
Short Range ◽  
Higher Order ◽  
Neutron Matter ◽  
S Wave ◽  
Short Range Correlations

Singlet S-wave superfluidity of dilute neutron matter in the inner crust of neutron stars is studied within the correlated BCS (Bardeen, Cooper, Schrieffer) method, taking into account both pairing and short-range correlations. First, the equation of state (EOS) of normal neutron matter is calculated within the correlated-basis-function (CBF) method in lowest cluster order using the Argonne V18 and V4′ potentials and Jastrow-type correlation functions. The 1S0 superfluid gap is then calculated with these potentials and correlation functions. The dependence of our results on the choice of the correlation functions is ana- lyzed and the role of higher-order cluster corrections is considered. The values obtained for the 1S0 gap within this simplified scheme are comparable to those from other, more elaborate, methods.

scholarly journals RECENT OBSERVATION OF SHORT-RANGE NUCLEON CORRELATIONS IN NUCLEI AND THEIR IMPLICATIONS FOR THE STRUCTURE OF NUCLEI AND NEUTRON STARS

2008 ◽  
Vol 23 (20) ◽  
pp. 2991-3055 ◽  
Author(s):  
LEONID FRANKFURT ◽  
MISAK SARGSIAN ◽  
MARK STRIKMAN
Keyword(s):  
Neutron Stars ◽  
Short Range ◽  
Degrees Of Freedom ◽  
Cold Neutron ◽  
Recent Observation ◽  
Experimental Studies ◽  
Heavy Nuclei ◽  
Short Range Correlations ◽  
Fast Removal

Novel processes probing the decay of nucleus after removal of a nucleon with momentum larger than Fermi momentum by hard probes finally proved unambiguously the evidence for long sought presence of short-range correlations (SRC's) in nuclei. In combination with the analysis of large Q2, A(e, e')X processes at x > 1 they allow us to conclude that (i) practically all nucleons with momenta ≥ 300 MeV /c belong to SRC's, consisting mostly of two nucleons, (ii) probability of such SRC's in medium and heavy nuclei is ~25%, (iii) a fast removal of such nucleon practically always leads to emission of correlated nucleon with approximately opposite momentum, (iv) proton removal from two-nucleon SRC's in 90% of cases is accompanied by a removal of a neutron and only in 10% by a removal of another proton. We explain that observed absolute probabilities and the isospin structure of two nucleon SRC's confirm the important role that tensor forces play in internucleon interactions. We also find that the presence of SRC's requires modifications of the Landau Fermi liquid approach to highly asymmetric nuclear matter and leads to a significantly faster cooling of cold neutron stars with neutrino cooling operational even for Np/Nn ≤ 0.1. The effect is even stronger for the hyperon stars. Theoretical challenges raised by the discovered dominance of nucleon degrees of freedom in SRC's and important role of the spontaneously broken chiral symmetry in quantum chromodynamics (QCD) in resolving them are considered. We also outline directions for future theoretical and experimental studies of the physics relevant for SRC's.

scholarly journals The role of mass, equation of state, and superfluid reservoir in large pulsar glitches

2020 ◽  
Vol 492 (4) ◽  
pp. 4837-4846 ◽  
Author(s):  
A Montoli ◽  
M Antonelli ◽  
P M Pizzochero
Keyword(s):  
Neutron Star ◽  
Equation Of State ◽  
Neutron Stars ◽  
Small Region ◽  
Outer Core ◽  
Rotational Dynamics ◽  
Internal Layers ◽  
S Wave ◽  
Average Activity

ABSTRACT Observations of pulsar glitches may provide insights on the internal physics of neutron stars and recent studies show how it is in principle possible to constrain pulsar masses with timing observations. The reliability of these estimates depends on the current uncertainties about the structure of neutron stars and on our ability to model the dynamics of the superfluid neutrons in the internal layers. We assume a simplified model for the rotational dynamics of a neutron star and estimate an upper bound to the mass of 25 pulsars from their largest glitch and average activity: the aim is to understand to which extent the mass constraints are sensitive to the choice of the unknown structural properties of neutron stars, like the extension of the superfluid region and the equation of state. Reasonable values, within the range measured for neutron star masses, are obtained only if the superfluid domain extends for at least a small region inside the outer core, which is compatible with calculations of the neutron S-wave pairing gap. Moreover, the mass constraints stabilize when the superfluid domain extends to densities over nuclear saturation, irrespective of the equation of state tested.

scholarly journals QUARK–DIQUARK EQUATIONS OF STATE MODELS: THE ROLE OF INTERACTIONS

2003 ◽  
Vol 12 (03) ◽  
pp. 519-526 ◽  
Author(s):  
J. E. HORVATH ◽  
G. LUGONES ◽  
J. A. DE FREITAS PACHECO
Keyword(s):  
Equation Of State ◽  
Boundary Conditions ◽  
Neutron Stars ◽  
Hard Sphere ◽  
Degrees Of Freedom ◽  
Equations Of State ◽  
Compact Star ◽  
Star Models ◽  
State Models

Recent observational data suggests a high compacticity (the quotient M/R) of some "neutron" stars. Motivated by these works we revisit models based on quark–diquark degrees of freedom and address the question of whether that matter is stable against diquark disassembling and hadronization within the different models. We find that equations of state modeled as effective λϕ4 theories do not generally produce stable self-bound matter and are not suitable for constructing very compact star models, that is the matter would decay into neutron matter. We also discuss some insights obtained by including hard sphere terms in the equation of state to model repulsive interactions. We finally compare the resulting equations of state with previous models and emphasize the role of the boundary conditions at the surface of compact self-bound stars, features of a possible normal crust of the latter and related topics.

scholarly journals Magnetic frustration, short-range correlations and the role of the paramagnetic Fermi surface of PdCrO2

2015 ◽  
Vol 5 (1) ◽  
Author(s):  
David Billington ◽  
David Ernsting ◽  
Thomas E. Millichamp ◽  
Christopher Lester ◽  
Stephen B. Dugdale ◽  
...  
Keyword(s):  
Fermi Surface ◽  
Short Range ◽  
Magnetic Frustration ◽  
Short Range Correlations

STABILITY OF NEUTRON STARS WITH LARGE AMOUNT OF STRANGENESS AND THE ROLE OF δ-MESON

2007 ◽  
Vol 16 (09) ◽  
pp. 2855-2858 ◽  
Author(s):  
M. RAZEIRA ◽  
A. MESQUITA ◽  
C. A. Z. VASCONCELLOS ◽  
B. E. J. BODMANN ◽  
M. DILLIG ◽  
...  
Keyword(s):  
Neutron Star ◽  
Equation Of State ◽  
Neutron Stars ◽  
Nuclear Matter ◽  
Lagrangian Density ◽  
Stability Conditions ◽  
Meson Field ◽  
Strange Quarks ◽  
Strangeness Content

We investigate the role of the strange σ*, ϕ and δ meson fields on the delineation of main properties of neutron stars using a parameterized Lagrangian density model in the effective baryon and meson sectors. We assume, strange quarks are localized within the hyperon fields, which carry the strangeness content of the model. Our main goal is to analyze stability conditions of neutron stars with large amount of strangeness per baryon. Our main result indicates the inclusion of the strange (anti-)quark containing meson field σ*, besides ϕ and δ into nuclear matter, turn the equation of state stiffer this way increasing the gravitational mass of the neutron star.

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