1,721,029 research outputs found
Consistent nuclear matter calculations with local three-nucleon interactions
No full textI calculate the energy per particle of symmetric nuclear matter and pure neutron matter in the framework of the microscopic Brueckner-Hartree-Fock approach using some recent interactions derived in chiral perturbation theory at next-to-next-to-next-to-leading order (N3LO) for the nucleon-nucleon (NN) force, and next-to-next-to-leading order (N2LO) for the nucleon-nucleon-nucleon (NNN) one. The interactions considered in the present work have been adjusted to properties of light nuclei with A=3, adopting local regulators for the NNN interaction. I performed several calculations using an effective density dependent two-body force obtained from the original NNN one keeping the same parameters and the same regularization scheme employed in finite light nuclei calculations; I then compared these results with other calculations obtained, retaining the same parameters of the NNN force fixed on light nuclei but using a nonlocal regulator. This second strategy has been often used in the literature due to the easier derivation of the effective NN force in this case. I found that in pure neutron matter the use of local or nonlocal regulators does not sensibly affect the calculation of the energy per particle while in symmetric nuclear matter the use of local or nonlocal regulators produces appreciable differences. Saturation properties of nuclear matter are discussed for the various models considered; the uncertainties on the reported calculations are also estimated
Hyperons in Neutron Stars
No full textI review the issues related to the appearance of hyperons in neutron star matter, focusing in particular on the problem of the maximum mass supported by hyperonic equations of state. I discuss the general mechanism that leads to the formation of hyperons in the core of neutron stars and I review the main techniques and many-body methods used to construct an appropriate equation of state to describe the strongly interacting system of hadrons hosted in the core of neutron stars. I outline the consequences on the structure and internal composition of neutron stars and also discuss the possible signatures of the presence of hyperons in astrophysical dynamical systems like supernova explosions and binary neutron star mergers. Finally, I briefly report about the possible important role played by hyperons in the transport properties of neutron star matter and on the consequences of neutron star cooling and gravitational wave instabilities induced by the presence of hyperons
Optimized chiral N2LO interactions in nuclear matter
No full textWe employ modern two- and three-nucleon interactions derived in chiral perturbation theory (ChPT) at next to-next-to leading order (N2LO), to calculate the energy per particle of symmetric nuclear matter and pure neutron matter in the framework of the microscopic Brueckner-Hartree-Fock approach. In particular, we present results concerning two optimized versions at N2LO of chiral potentials (), fitted to properties of light nuclei. We also employ the recently developed interaction which has been calculated at the same order of ChPT but fitted in a very different way compared with the interactions. We find that using these potentials, in general, it is not possible to reproduce all the saturation properties of nuclear matter. In particular the behaviour of the symmetry energy ( predicted by the interactions considered is quite soft. This is shown comparing our results with the empirical constraints on obtained from the data analysis of the excitation energies of isobaric analog states in nuclei and from experimental data of the neutron skin thickness of heavy nuclei. We finally confront our results with similar calculations performed by other research groups using nuclear chiral interactions at various order of ChPT and employing different many-body methods
Constraints on hybrid neutron stars equation of state from neutron stars merging
No full textUsing recent gravitational and electromagnetic constraints on the neutron star matter equation of state (EOS) coming from the merge of two neutron stars, we study the physical conditions for which a quark deconfinement phase transition in cold neutron star matter is consistent with these new measurements. To this end, we consider several microscopic EOSs based on various ab initio approaches to describe the confined hadronic phase, and combine them with two phenomenological quark matter EOSs for the deconfined phase. The low and high density phases are then joined up through a mixed phase determined by a Gibbs construction. For each EOS we calculate the dimensionless binary deformability parameter Λ ̃ which can be directly related to the constraints derived from the gravitational waves detection. We find that in order to see any difference between the pure hadronic and the hadron-quark EOS for neutron stars with mass in the range (1.4-1.6) M⊙ through the calculation of Λ ̃ , the EOSs of both hadronic and quark matter should be quite stiff, otherwise the variation on Λ ̃ can be valued just on neutron star masses above 1.8 M⊙ which currently are not constrained by present gravitational waves data. We find in addition that the softening of the hadronic EOS induced by the quark deconfinement phase transition can change the compatibility of a given hadronic EOS with the constraints obtained from neutron stars merging
Constraints on microscopic and phenomenological equations of state of dense matter from GW170817
Full text linkWe discuss the constraints on the equation of state (EOS) of neutron star matter obtained by the data analysis of the neutron star-neutron star merger in the event GW170807. To this scope, we consider two recent microscopic EOS models computed starting from two-body and three-body nuclear interactions derived using chiral perturbation theory. For comparison, we also use three representative phenomenological EOS models derived within the relativistic mean field approach. For each model, we determine the β-stable EOS and then the corresponding neutron star structure by solving the equations of hydrostatic equilibrium in general relativity. In addition, we calculate the tidal deformability parameters for the two neutron stars and discuss the results of our calculations in connection with the constraints obtained from the gravitational wave signal in GW170817. We find that the tidal deformabilities and radii for the binary's component neutron stars in GW170817, calculated using a recent microscopic EOS model proposed by the present authors, are in very good agreement with those derived by gravitational waves data
Neutron star properties from optimised chiral nuclear interactions
Full text linkWe adopt two- and three-body nuclear forces derived at the next-to-next-to-leading-order in the framework of effective chiral perturbation theory to calculate the equation of state of β-stable neutron star matter using the Brueckner-Hartree-Fock many-body approach. We use the recent optimized chiral two-body nuclear interaction at next-to-next-to-leading-order derived by Ekström et al. and two different parametrizations of the three-body next-to-next-to-leading-order interaction: the first one is fixed to reproduce the saturation point of symmetric nuclear matter while the second one is fixed to reproduce the binding energies of light atomic nuclei. We show that in the second case the properties of nuclear matter are not well determined whereas in the first case various empirical nuclear matter properties around the saturation density are well reproduced. We finally calculate various neutron star properties and in particular the mass-radius and mass-central density relations. We find that the adopted interactions based on a fully microscopic framework, are able to provide an equation of state which is consistent with the present data of measured neutron star masses
Quark deconfinement transition in neutron stars with the field correlator method
Full text linkA phase of strong interacting matter with deconfined quarks is expected in the core of massive neutron stars. In this article, we perform a study of the hadron--quark phase transition in cold () neutron star matter and we calculate various structural properties of hybrid stars. For the quark phase, we make use of an equation of state (EOS) derived with the Field Correlator Method (FCM) recently extended to the case of nonzero baryon density. For the hadronic phase, we consider both pure nucleonic and hyperonic matter, and we derive the corresponding EOS within a relativistic mean field approach. We make use of measured neutron star masses, and particularly the mass of PSR~J1614-2230, to constrain the values of the gluon condensate , which is one of the EOS parameter within the FCM. We find that the values of extracted from the mass measurement of PSR~J1614-2230 are consistent with the values of the same quantity derived, within the FCM, from recent lattice QCD calculations of the deconfinement transition temperature at zero baryon chemical potential. The FCM thus provides a powerful tool to link numerical calculations of QCD on a space-time lattice with measured neutron star masses
(La,Ba)SnO3-based thin-film transistors. Large-signal model and scaling projections
No full textPerovskite oxides are extremely interesting for their possible use in high-mobility thin-film transistors (TFTs) suitable for high-performance large-area circuits. Here we present a semianalytical model of a recently fabricated TFT based on La-BaSnO3, and explore the possibilities for technology optimization and the intrinsic potential of the device concept for applications in transparent and flexible electronics. We show that La-BaSnO3 TFTs can outperform existing TFT device technologies through a detailed benchmarking exercise, and that these devices can be promising for display electronics and for a broader range of applications
Two-meson exchange hyperonic three-body forces and consequences for neutron stars
No full textWe construct two-meson exchange three-baryon potentials between two nucleons and one hyperon (NNY) consistent with the two body nucleon-hyperon (NY) J04 potential of the Jülich group. In particular, we focus on the NNΛ and N Nσ - forces since Λ and σ - are the first hyperons expected to appear in microscopic calculations of neutron star matter. Brueckner-Hartree-Fock calculations of the hyperonic matter are then performed including the effect of these three-body forces. Our results show that at high densities the total contribution of the NNY force is repulsive making the resulting equation of state stiffer, as required from neutron star mass observations. © 2013 Elsevier B.V
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