The two-pion exchange NN potential in nuclear matter and nuclear stability

Rapp, Ralf; Durso, J.W.; Wambach, J.

doi:10.1016/s0375-9474(96)00482-4

Cited by 12 publications

(13 citation statements)

References 31 publications

(71 reference statements)

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“…But according to investigations of ter Haar and Malfliet [43], the ∆-mass does not change very much from the vacuum case, indicating smaller ∆-couplings, which would delay the onset of the ∆s. In a recent treatment by R. Rapp et al [44], the choice g ∆∆ = g ∆N = 0.625 g N N was recommended, but one could use as an option also this choice for the attraction only [14]. For the first case one gets a slight shift of the ∆-threshold towards higher densities (see Fig.…”

Section: β) Results and Discussionmentioning

confidence: 99%

Neutron Star Properties with Relativistic Equations of State

Huber

Weber

Weigel

et al. 1998

Int. J. Mod. Phys. E

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We study the properties of neutron stars adopting relativistic equations of state of neutron star matter, calculated in the framework of the relativistic Brueckner-Hartree-Fock approximation for electrically charge neutral neutron star matter in beta-equilibrium. For higher densities more baryons (hyperons etc.) are included by means of the relativistic Hartree-or Hartree-Fock approximation. The special features of the different approximations and compositions are discussed in detail. Besides standard neutron star properties special emphasis is put on the limiting periods of neutron stars, for which the Kepler criterion and gravitation-reaction instabilities are considered. Furthermore the cooling behaviour of neutron stars is investigated, too. For comparison we give also the outcome for some nonrelativistic equations of state. I IntroductionA necessary ingredient for solving the structure equations for (rotating) neutron stars (NS) is the equation of state (EOS) [1]. For NSs the EOS has to cover a wide range of densities ranging from super-nuclear densities (up to 5 to 10 times normal nuclear matter density) in the star's core down to the density of iron at the star's surface. At present, neither heavy-ion reactions nor NS data are capable to determine the EOS accurately, and the behaviour of high-density matter is still an open and one of the most challenging problems in modern physics, containing many ingredients from different branches of physics. The theoretical determination of the EOS over such an enormous range has therefore to rely mainly on theoretical arguments and extrapolations for which no direct experimental confirmation exists. The best one can do in such a situation is a step-by-step improvement of the available models for the EOS. Since the central density of a NS is so extreme, both the Fermi momenta and the effective nucleon mass are of the order of 500 MeV, one should prefer a relativistic description [2]- [9].Neutron star matter differs from the high density systems produced in heavy ion collisions by two essential features: a) Matter in high energy collisions is still governed by the charge symmetric nuclear force while neutron star matter (NSM) is bound by gravity. Since the repulsive Coulomb force is much stronger than the gravitational attraction, NSM is much more asymmetric than "standard" matter. b) The second essential difference is caused by the weak interaction time scale of ∼ 10 −10 s, which is small in comparison with the lifetime of the star, but large in comparison with the characteristic time scale of heavy ion reactions. For that reasons "normal" matter is subject to the constraints of isospin symmetry and strangeness conservation, but NSM has to obey the constraints of charge neutrality and generalized beta-equilibrium with no strangeness conservation. It is obvious from these considerations that NSM is an even more theoretical object than nuclear "normal" matter, with a rather complex structure [2]- [9].Due to these features one can adopt the following structure o...

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Section: β) Results and Discussionmentioning

confidence: 99%

Neutron Star Properties with Relativistic Equations of State

Huber

Weber

Weigel

et al. 1998

Int. J. Mod. Phys. E

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“…By correcting this feature, one obtains lower scalar couplings (see Table 3 For this EOS the^s contribute significantly, since the strong coupling of the As in combination with the weaker p-coupling is capable to overcome their iso-spin unfavoured deficit. However decrease of the Z\-coupling according to [15] is sufficient to push out again the iso-spin un- 3 s -1 . The outcome for the RHF is depicted in Fig.…”

Section: Rhf -Approximation Rh3mentioning

confidence: 97%

Compatibility of Neutron Star Masses and Hyperon Coupling Constants

Huber

Weigel

Weber

1999

Zeitschrift Für Naturforschung A

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It is shown that the modern equations of state for neutron star matter based on microscopic calculations of symmetric and asymmetric nuclear matter are compatible with the lower bound on the maximum neutron-star mass for a certain range of hyperon coupling constants, which are constrained by the binding energies of hyperons in symmetric nuclear matter. The hyperons are included by means of the relativistic Hartree-or Hartree-Fock approximation. The obtained couplings are also in satisfactory agreement with hypernuclei data in the relativistic Hartree scheme. Within the relativistic Hartree-Fock approximation, hypernuclei have not been investigated so far.PACS 97.60.7d, 26.60,+c, 21.80.+a, 21.65.+f Neutron star matter (NSM), bound by gravity, differs from high density nuclear matter produced in heavy ion reactions in several respects: 1) Since the repulsive Coulomb force is much stronger than the gravitational attraction, NSM is much more asymmetric than terrestrial matter in heavy ion collisions.2) The weak interaction time scale is small in comparison with the lifetime of the neutron star (NS), but large in comparison with the lifetime of high-density matter in heavy ion reactions. For that reasons dense matter in high-energy reactions has to obey the constraints of isospin symmetry and strangeness conservation whereas NSM is a charge neutral system with no strangeness conservation (see, for instance, [1] ax) = Y, B=p,n,l±° ,A,E°---,A--C°B(x)+with further references). Extraterrestrial NSM is for that reasons a rather theoretical object with a very complex structure. Since its density stretches over an enormous range, reaching from crystalline iron on the surface to several times of nuclear matter saturation density in the core, one encounters in the theoretical descriptions many obstacles, for which one has to introduce theoretical assumptions and extrapolations [1, 2], However one can try to combine both high density systems in a common theory, which is possible in modern field theoretical approaches. The first systematic investigation in this respect was performed by Glendenning [3], who used the standard nuclear relativistic Lagrangian extended by inclusion of hyperons and deltas, i. e. M=<7,UJ,IR,P,6

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“…However, as was conjectured in Ref. [16], the inclusion of density-dependent meson masses and coupling constants in the ππ interaction kernel might provide a remedy to this problem. Here we work at mean field level, changing only f * π and masses according to…”

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confidence: 88%

Nuclear Saturation with In-Medium Meson Exchange Interactions

et al. 1999

Self Cite

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We show that the assumption of dropping meson masses together with conventional many-body effects, implemented in the relativistic Dirac-Brueckner formalism, explains nuclear saturation. We use a microscopic model for correlated 2π exchange and include the standard many-body effects on the in-medium pion propagation, which initially increase the attractive nucleon-nucleon (N N ) potential with density. For the vector meson exchanges in both the ππ and N N sector, we assume Brown-Rho scaling which-in concert with 'chiral' ππ contact interactions-reduces the attraction at higher densities.

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The two-pion exchange NN potential in nuclear matter and nuclear stability

Cited by 12 publications

References 31 publications

Neutron Star Properties with Relativistic Equations of State

Neutron Star Properties with Relativistic Equations of State

Compatibility of Neutron Star Masses and Hyperon Coupling Constants

Nuclear Saturation with In-Medium Meson Exchange Interactions

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