Impact of chiral hyperonic three-body forces on neutron stars

Abstract

We study the effect of the nucleon-nucleon-lambda (NNΛ) three-body force on neutron stars. In particular, we consider the NNΛ force recently derived by the Jülich-Bonn-Munich group within the framework of chiral effective field theory at next-to-next-to-leading order. This force, together with realistic nucleon-nucleon, nucleon-nucleon-nucleon and nucleon-hyperon interactions, is used to calculate the equation of state and the structure of neutron stars within the many-body non-relativistic Brueckner-Hartree-Fock approach. Our results show that the inclusion of the NNΛ force leads to an equation of state stiff enough such that the resulting neutron star maximum mass is compatible with the largest currently measured (∼ 2 M ⊙ ) neutron star masses. Using a perturbative many-body approach we calculate also the separation energy of the Λ in some hypernuclei finding that the agreement with the experimental data improves for the heavier ones when the effect of the NNΛ force is taken into account.

Microscopic equation of state of hot nuclear matter for numerical relativity simulations

“…Work in this direction is ongoing. Specifically, we are currently trying to extend our present calculations to the case of finite-temperature hyperonic matter, adopting nucleon-hyperon (Haidenbauer et al 2013) and hyperon-hyperon (Haidenbauer et al 2016) interactions derived in the framework of ChPT, and to include hyperonic three-body forces like those in the zero-temperature case discussed by Logoteta et al (2019).…”

Transport Coefficients of Hyperonic Neutron Star Cores

“…Various methods have been considered to solve the nuclear many-body problem: the variational approach [57], the correlated basis function (CBF) formalism [58], the self-consistent Green's function (SCGF) technique [59,60], or the Brueckner-Bethe-Goldstone (BBG) [61] and the Dirac-Bruecker-Hartree-Fock (DBHF) theories [62][63][64]. Nevertheless, although all of them have been extensively applied to the study of nuclear matter, up to our knowledge, only the BBG theory in the BHF approximation [13][14][15][16][17][18][19]22,25,26], and very recently the DBHF theory [20], the V-low-k approach [21], and the quantum Monte Carlo method [23,24] have been extended to the hyperonic sector.…”

“…However, at densities of about (2-3)n 0 simple energy arguments suggest that other baryonic degrees of freedom, such as, for instance, hyperons, can appear. This possibility was first proposed by Ambartsumyan and Saakyan [2] in 1960 and it has been later extensively studied in great detail by many authors using different phenomenological [3][4][5][6][7][8][9][10][11][12] or microscopical [13][14][15][16][17][18][19][20][21][22][23][24][25][26] approaches to the equation of state (EOS) of NS matter with hyperons. However, although the presence of hyperons in NSs seems to be energetically unavoidable, the softening that their presence induces on the EOS leads to NS maximum masses which are incompatible with the observation of the unusually high masses of the millisecond pulsars PSR J1903 + 0327 (1.667 ± 0.021 M ) [27], PSR J1614−2230 (1.928 ± 0.017 M ) [28], PSR J0348 + 0432 (2.01 ± 0.04 M ) [29] and the most recent one PSR J0740+6620 (2.14 +0.10 −0.09 M ) [30].…”

Hyperon-Nuclear Interactions From SU(3) Chiral Effective Field Theory

“…(102), and on the other hand the starting energy of the G-matrix elements depends on U through the single-particle energies E i in Eq. (103). At the (leading) level of two hole-lines, called Brueckner-Hartree-Fock approximation (BHF), the total energy is given by…”

“…Chiral three-nucleon forces are important in order to get saturation of nuclear matter from chiral low-momentum two-body interactions treated in many-body perturbation theory [63]. In the strangeness sectors the situation is similar: Threebaryon forces (3BF), especially the ΛN N interaction, seem to be important for a satisfactorily description of hypernuclei and hypernuclear matter [58,[95][96][97][98][99][100][101][102][103]. Especially in the context of neutron stars, 3BF are frequently discussed.…”