Only one-third of the nucleons in 208Pb occupy the saturation density area. Consequently, nuclear observables related to the average properties of nuclei, such as masses or radii, constrain the ...equation of state not at the saturation density but rather around the so-called crossing density, localized close to the mean value of the density of nuclei: ρ is approximately equal to 0.11 fm(-3). This provides an explanation for the empirical fact that several equation of state quantities calculated with various functionals cross at a density significantly lower than the saturation one. The third derivative M of the energy per unit of volume at the crossing density is constrained by the giant monopole resonance measurements in an isotopic chain rather than the incompressibility at saturation density. The giant monopole resonance measurements provide M=1100±70 MeV (6% uncertainty), whose extrapolation gives K(∞)=230±40 MeV (17% uncertainty).
Neutron stars and the nuclear equation of state Burgio, G.F.; Schulze, H.-J.; Vidaña, I. ...
Progress in particle and nuclear physics,
September 2021, 2021-09-00, Volume:
120
Journal Article
Peer reviewed
We review the current status and recent progress of microscopic many-body approaches and phenomenological models, which are employed to construct the equation of state of neutron stars. The equation ...of state is relevant for the description of their structure and dynamical properties, and it rules also the dynamics of core-collapse supernovae and binary neutron star mergers. We describe neutron star matter assuming that the main degrees of freedom are nucleons and hyperons, disregarding the appearance of quark matter. We compare the theoretical predictions of the different equation-of-state models with the currently available data coming from both terrestrial laboratory experiments and recent astrophysical observations. We also analyze the importance of the nuclear strong interaction and equation of state for the cooling properties of neutron stars. We discuss the main open challenges in the description of the equation of state, mainly focusing on the limits of the different many-body techniques, the so-called “hyperon puzzle,” and the dependence of the direct URCA processes on the equation of state.
We investigate the possibility that the low mass companion of the black hole in the source of GW190814 was a strange quark star. This possibility is viable within the so-called two-families scenario ...in which neutron stars and strange quark stars coexist. Strange quark stars can reach the mass range indicated by GW190814, M∼(2.5-2.67) M_{⊙} due to a large value of the adiabatic index, without the need for a velocity of sound close to the causal limit. Neutron stars (actually hyperonic stars in the two-families scenario) can instead fulfill the presently available astrophysical and nuclear physics constraints which require a softer equation of state. In this scheme it is possible to satisfy both the request of very large stellar masses and of small radii while using totally realistic and physically motivated equations of state. Moreover it is possible to get a radius for a 1.4 M_{⊙} star of the order or less than 11 km, which is impossible if only one family of compact stars exists.
We have conducted a study of the femtoscopic correlation functions for the D0D⁎+ and D+D⁎0 channels that build the Tcc state. We develop a formalism that allows us to factorize the scattering ...amplitudes outside the integrals in the formulas, and the integrals involve the range of the strong interaction explicitly. For a source of size of 1 fm, we find values for the correlation functions of the D0D⁎+ and D+D⁎0 channels at the origin around 30 and 2.5, respectively, and we see these observables converging to unity already for relative momenta of the order of 200 MeV. We conduct tests to see the relevance of the different contributions to the correlation function and find that it mostly provides information on the scattering length, but should the correlation functions be measured with the precision of the latest experiments, the effective range of the D0D⁎+ could also be obtained.
Elucidating the appropriate microscopic degrees of freedom within neutron stars remains an open question which impacts nuclear physics, particle physics and astrophysics. The recent discovery of the ...first non-trivial dibaryon, the d⁎(2380), provides a new candidate for an exotic degree of freedom in the nuclear equation of state at high matter densities. In this paper a first calculation of the role of the d⁎(2380) in neutron stars is performed based on a relativistic mean field description of the nucleonic degrees of freedom supplemented by a free boson gas of d⁎(2380). The calculations indicate that the d⁎(2380) would appear at densities around three times normal nuclear matter saturation density and comprise around 20% of the matter in the centre of heavy stars with higher fractions possible in the higher densities of merger processes. The d⁎(2380) would also reduce the maximum star mass by around 15% and have significant influence on the fractional proton/neutron composition. New possibilities for neutron star cooling mechanisms arising from the d⁎(2380) are also predicted.
Experimental studies of nuclear fission induced by fusion, transfer, spallation, fragmentation, and electromagnetic reactions in combination with state-of-the-art calculations are successful to ...investigate the nuclear dissipation mechanism in normal nuclear matter, containing only nucleons. The dissipation mechanism has been widely studied by the use of many different fission observables and nowadays the dissipation coefficients involved in transport theories are well constrained. However, the existence of hypernuclei and the possible presence of hyperons in neutron stars make it necessary to extend the investigation of the nuclear dissipation coefficient to the strangeness sector. In this Letter, we use fission reactions of hypernuclei to constrain for the first time the dissipation coefficient in hypernuclear matter, observing that this coefficient increases a factor of 6 in the presence of a single Λ hyperon with respect to normal nuclear matter.
In this paper we present a novel method to extract information on hadron-hadron interactions using for the first time femtoscopic data to constrain the low-energy constants of a QCD effective ...Lagrangian. This method offers a new way to investigate the nonperturbative regime of QCD in sectors where scattering experiments are not feasible, such as the multistrange and charm ones. As an example of its application, we use the very precise K − Λ correlation function data, recently measured in p p collisions at LHC, to constrain the strangeness S = − 2 meson-baryon interaction. The model obtained delivers new insights on the molecular nature of the Ξ ( 1620 ) and Ξ ( 1690 ) states. Published by the American Physical Society 2024
We study the structure of single
Λ
-hypernuclei using the Hartree–Fock–Bogoliubov method. Finite range Gogny-type forces are used to describe the nucleon–nucleon and
Λ
-nucleon interactions. Three ...different
Λ
-nucleon Gogny forces are built. The unknown parameters of these forces are obtained by fitting the experimental binding energies of the 1
s
Λ
single-particle state in various hypernuclei using the “Simulated Annealing Method”. These forces are then used to calculate the binding energies of the other (1
p
, 1
d
, 1
f
, 1
g
)
Λ
single-particle states in the different hypernuclei. The predicted values are found to be in good agreement with the experimental data for the three forces constructed. In addition, we calculate also the root-mean-square radii of ground state
Λ
orbital, as well as several global properties of the hypernuclei considered such as their ground-state Hartree–Fock–Bogoliubov energy, their pairing energy and their quadrupole moment.
We present the extension of a previous study where, assuming a simple free bosonic gas supplemented with a relativistic mean-field model to describe the pure nucleonic part of the equation of state, ...we studied the consequences that the first non-trivial hexaquark
d
*
(2380) could have on the properties of neutron stars. Compared to that exploratory work, we employ a standard non-linear Walecka model including additional terms that describe the interaction of the
d
*
(2380) di-baryon with the other particles of the system through the exchange of
σ
- and
ω
-meson fields. Our results show that the presence of the
d
*
(2380) leads to maximum masses compatible with recent observations of ∼2
M
⊙
millisecond pulsars if the interaction of the
d
*
(2380) is slightly repulsive or the
d
*
(2380) does not interact at all. An attractive interaction makes the equation of state too soft to be able to support a 2
M
⊙
neutron star whereas an extremely repulsive one induces the collapse of the neutron star into a black hole as soon as the
d
*
(2380) appears.
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