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 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 QCD AND QED DYNAMICS IN THE EMC EFFECT

2012 ◽  
Vol 21 (04) ◽  
pp. 1230002 ◽  
Author(s):  
LEONID FRANKFURT ◽  
MARK STRIKMAN
Keyword(s):  
Structure Function ◽  
Degrees Of Freedom ◽  
Experimental Studies ◽  
Momentum Conservation ◽  
Light Nuclei ◽  
Heavy Nuclei ◽  
Fermi Motion ◽  
Nucleon Wave Function ◽  
Emc Effect ◽  
Bjorken X

Applying exact QCD sum rules for the baryon charge and energy–momentum conservation we demonstrate that if the only degrees of freedom in nuclei were nucleons, the structure function of a nucleus would be the additive sum of the nucleon distributions at the same Bjorken x = AQ2/2(pA⋅q)≤0.5 up to very small Fermi motion corrections if 1/2mN x is significantly less than the nucleus radius. Hence QCD implies that the proper quantity to reveal violation of the additivity due to presence of nonnucleonic degrees of freedom in nuclei is the ratio RA(x, Q2) = (2/A)F2A(x, Q2)/F2D(x, Q2). Use of variable xp = Q2/2q0mp in the experimental studies instead of x leads to the deviation of RA(xp, Q2) from one even if the nucleus would consist only of nucleons with small momenta. Implementation of QCD dynamics accounts in the case of the light nuclei for at least a half of the deviation of RA(xp, Q2) from one for x≤0.55. In the case of heavy nuclei account of the QCD dynamics and of light-cone momentum fraction carried by Fermi, Weizsacker, Williams equivalent photons are responsible for ≈ one half the deviation of RA(x, Q2) from one at x≤0.55. We argue that direct observation of large and predominantly nucleonic short-range correlations (SRCs) in nuclei impacts strongly on the understanding of the EMC effect for x≥0.6 posing a serious challenge for most of the proposed models of the EMC effect. The data are consistent with a scenario in which the hadronic EMC effect reflects suppression of rare quark–gluon configurations in nucleons belonging to SRC appears to be the only viable. The dynamic realization of this scenario is presented in which quantum fluctuations of the nucleon wave function with x≥0.5 parton have a weaker interaction with nearby nucleons, leading to suppression of such configurations in bound nucleons and to the significant suppression of nucleon Fermi motion effects at x≥0.55 giving a right magnitude of the EMC effect. Implications of discussed effects for the analyses of the neutron structure function and nuclear parton distributions are presented. The directions for the future studies and challenging questions are outlined.

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 The State of Matter in Simulations of Core-Collapse supernovae—Reflections and Recent Developments

2017 ◽  
Vol 34 ◽  
Author(s):  
Tobias Fischer ◽  
Niels-Uwe Bastian ◽  
David Blaschke ◽  
Mateusz Cierniak ◽  
Matthias Hempel ◽  
...  
Keyword(s):  
Equation Of State ◽  
Degrees Of Freedom ◽  
The State ◽  
Core Collapse ◽  
Heavy Nuclei ◽  
Isospin Asymmetry ◽  
Wide Range ◽  
Recent Developments ◽  
State Of Matter

AbstractIn this review article, we discuss selected developments regarding the role of the equation of state in simulations of core-collapse supernovae. There are no first-principle calculations of the state of matter under supernova conditions since a wide range of conditions is covered, in terms of density, temperature, and isospin asymmetry. Instead, model equation of state are commonly employed in supernova studies. These can be divided into regimes with intrinsically different degrees of freedom: heavy nuclei at low temperatures, inhomogeneous nuclear matter where light and heavy nuclei coexist together with unbound nucleons, and the transition to homogeneous matter at high densities and temperatures. In this article, we discuss each of these phases with particular view on their role in supernova simulations.

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

scholarly journals Effect of oxygen nonstoichiometry on magnetic phase transitions in frustrated cobaltites YBaCo4O7+x (x = 0, 0.1, 0.2)

2018 ◽  
Vol 185 ◽  
pp. 06004
Author(s):  
Zoya Kazei ◽  
Vyacheslav Snegirev ◽  
Ludmila Kozeeva ◽  
Margarita Kameneva ◽  
Alexander Lavrov
Keyword(s):  
Short Range ◽  
Room Temperature ◽  
Structural Transition ◽  
Magnetic Phase ◽  
Experimental Studies ◽  
Oxygen Nonstoichiometry ◽  
Magnetic Phase Transitions ◽  
Small Deviations ◽  
Effect Of Oxygen ◽  
Short Range Correlations

Experimental studies were carried out for structural and elastic properties of cobaltites YBaCo4O7+x (x = 0, 0.1, 0.2) obtained by various technologies and distinguished by oxygen content. Correlation was revealed between the structure distortion at room temperature and a hysteresis in a ΔE(T)/T0 curve in the temperature range 80 – 280 K, as well as the anomaly value in the region of TN. It was found, that small deviations from stoichiometry (x = 0.1, 0.2) result in suppression of structural transition, reduce a hysteresis, quickly smooth out and reduce anomalies of the Young’s modulus ΔE(T)/T0 in the range of magnetic phase transition. This behavior indicates that structural and magnetic transitions are suppressed in nonstoichiometric samples and only short range correlations of order parameters are retained

NEUTRON STARS WITH PARAMETRIZED MESON COUPLINGS

2000 ◽  
Vol 15 (29) ◽  
pp. 1789-1800 ◽  
Author(s):  
A. R. TAURINES ◽  
C. A. Z. VASCONCELLOS ◽  
M. MALHEIRO ◽  
M. CHIAPPARINI
Keyword(s):  
Neutron Stars ◽  
Nuclear Matter ◽  
Degrees Of Freedom ◽  
Scalar Meson ◽  
Mean Field Theory ◽  
Mean Field ◽  
Static Properties ◽  
Relativistic Mean Field ◽  
Specific Choice

We investigate static properties of nuclear and neutron star matter by using a relativistic mean field theory with parametrized couplings. With a suitable choice of mathematical parameters, the couplings allow one to reproduce results of current quantum hadrodynamics models. For other parametrizations, a better description of bulk properties of nuclear matter is obtained. The formalism is extended to include hyperon and lepton degrees of freedom, and an analysis on the effects of the phenomenological couplings in the fermion populations and mass of neutron stars is performed. The results show a strong similarity between the predictions of ZM-like models and those with exponential couplings. We have observed in particular an extreme sensibility of the predictions of these theories on the specific choice of the values of the binding energy of nuclear matter and saturation density. Additionally, the role of the very intense scalar meson mean field found in the interior of neutron stars in the screening of the nucleon mass is discussed.

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