AV18 Potential Research Articles

Local position-space two-nucleon potentials from leading to fourth order of chiral effective field theory

We present local, position-space chiral NN potentials through four orders of chiral effective field theory ranging from leading order (LO) to next-to-next-to-next-to-leading order (N3LO, fourth order) of the Delta-less version of the theory. The long-range parts of these potentials are fixed by the very accurate pi-N LECs as determined in the Roy-Steiner equations analysis. At the highest order (N3LO), the NN data below 190 MeV laboratory energy are reproduced with the respectable chi^2/datum of 1.45. A comparison of the N3LO potential with the phenomenological Argonne v_18 (AV18) potential reveals substantial agreement between the two potentials in the intermediate range ruled by chiral symmetry, thus, providing a chiral underpinning for the phenomenological AV18 potential. Our chiral NN potentials may serve as a solid basis for systematic ab initio calculations of nuclear structure and reactions that allow for a comprehensive error analysis. In particular, the order by order development of the potentials will make possible a reliable determination of the truncation error at each order. Our new family of local position-space potentials differs from existing potentials of this kind by a weaker tensor force as reflected in relatively low D-state probabilities of the deuteron (P_D less or equal 4.0% for our N3LO potentials) and predictions for the triton binding energy above 8.00 MeV (from two-body forces alone). As a consequence, our potentials may lead to different predictions when applied to light and intermediate-mass nuclei in ab initio calculations and, potentially, help solve some of the outstanding problems in microscopic nuclear structure.

Geometrical properties of ΩNN three-body states by realistic NN and first principles Lattice QCD ΩN potentials

The Faddeev equations in coordinate space are solved to study the ΩNN and ΩΩN three-body systems using the latest ΩNS25 and ΩΩ S01 interactions developed by the HAL QCD Collaboration. We recalculate the binding energy of the ΩNN system by examining three NN potentials, i.e., modern realistic AV18 potential, Yukawa-type Malfliet-Tjon (MT) interaction, and Gogny-Pires-Tourreil (GPT) soft and local potential. We take into account the contribution of the Coulomb potential. Our numerical calculations for Ωd(T=0) in maximum spin 5/2+ confirm ground state binding energy of 20.953, 19.368, and 20.439 MeV and a matter radius of 1.097, 1.373, and 1.309 fm using MT, GPT, and AV18 NN potentials, respectively. In the case of Ωd(0)5/2+ system, our numerical analysis shows that considering higher partial waves than s wave in NN interactions leads to an increase of about 0.2 MeV using GPT and about 0.1 MeV reduction with AV18 potentials. We study the convergence of three-body binding energies in a cluster model using the hyperspherical harmonics method and investigate the geometrical properties of Ωd(0)5/2+ ground states.

Binary neutron star mergers within kaon condensation:GW170817

The equation of state (EoS) of neutron star (NS) matter is investigated considering kaon condensation. Moreover, the tidal parameters related to the components of binary neutron star mergers are determined and compared to the constraints of GW170817 imposed on these quantities. In this study, we employ the lowest-order constrained variational (LOCV) approach and utilize AV6’, AV8’, and AV18 potentials accompanied by the three nucleon interaction (TNI) in order to consider the nucleon-nucleon interaction. It is known that the existence of kaons in the core of NSs softens the EoS and thus lowers the value of maximum mass which is expected to be greater than 2 M⊙. Our results demonstrate that considering kaon condensation with a strangeness value, a3 m s = −134 MeV satisfies the maximum mass constraint except for AV8’+TNI potential. However, the calculation of dimensionless tidal deformability shows that with the decrease of strangeness value, the neutron star gets less deformed.

Incoherent deeply virtual Compton scattering off He4

Very recently, for the first time, the two channels of nuclear deeply virtual Compton scattering (DVCS), the coherent and incoherent ones, have been separated by the CLAS collaboration at JLab, using a $^4$He target. The incoherent channel, which can provide a tomographic view of the bound proton and shed light on its elusive parton structure, is thoroughly analyzed here in Impulse Approximation (IA). A convolution formula for the cross sections in terms of those for the bound proton is derived. Novel scattering amplitudes for a bound moving nucleon have been obtained and used. A state-of-the-art nuclear spectral function, based on the AV18 potential, exact in the two-body part, with the recoiling system in its ground state, and modelled in the remaining contribution, with the recoiling system in an excited state, has been used. Different parametrizations of the generalized parton distributions of the struck proton have been tested. A good overall agreement with the data for the beam spin asymmetry (BSA) is obtained. It is found that the predicted conventional nuclear effects are relevant in DVCS and in the competing Bethe-Heitler mechanism, but they cancel each other to a large extent in their ratio, to which the measured asymmetry is proportional. Besides, the calculated ratio of the BSA of the bound proton to that of the free one does not describe that estimated by the experimental collaboration. This points to possible interesting effects beyond the IA analysis presented here. It is therefore clearly demonstrated that the comparison of the results of a conventional realistic approach, as the one presented here, with future precise data, has the potential to expose quark and gluon effects in nuclei. Interesting perspectives for the next measurements at high luminosity facilities, such as JLab at 12 GeV and the future EIC, are addressed.

Generalized contact formalism analysis of the 4He(e,e′pN) reaction

Measurements of short-range correlations in exclusive 4He(e,e′pN) reactions are analyzed using the Generalized Contact Formalism (GCF). We consider both instant-form and light-cone formulations with both the AV18 and local N2LO(1.0) nucleon-nucleon (NN) potentials. We find that kinematic distributions, such as the reconstructed pair opening angle, recoil neutron momentum distribution, and pair center of mass motion, as well as the measured missing energy, missing mass distributions, are all well reproduced by GCF calculations. The missing momentum dependence of the measured 4He(e,e′pN)/4He(e,e′p) cross-section ratios, sensitive to nature of the NN interaction at short-distacnes, are also well reproduced by GCF calculations using either interaction and formulation. This gives credence to the GCF scale-separated factorized description of the short-distance many-body nuclear wave-function.

The effect of the three-body force on the β-stable matter in RLOCV framework

The symmetry energy of isospin asymmetric nuclear matter (IANM), the density dependence of symmetry energy and also the equation of state (EOS) of the β-stable matter (BSM) are considered within relativistic corrections in the lowest order constrained variation approach (RLOCV) by using AV18 potential, with and without including Urbana (UIX) three-body force (TBF). The relative proton abundance for a wide range of baryon number density is calculated by including TBF in RLOCV approach. It is observed that if the bare two-body force (2BF) interaction AV18 is used, the relative proton abundance (ρp/ρB) increases by increasing baryon number density which tends to be saturated at high densities in both relativistic and non-relativistic treatments, while including TBF to our potential produces the ρp/ρB with higher values at low densities, which is saturated at the moderate densities in both LOCV and RLOCV frameworks. Moreover, adding the relativistic corrections (RC) to the results of β-stable matter decreases the value of proton abundance. In contrast, including TBF increases the value of ρp/ρB at low baryonic densities, which is saturated at the moderate baryon number densities. The opposite behaviors are also found on the saturation properties of nuclear matter by including TBF and RC to our calculations. It is also shown that the effect of TBF is much larger than that of the RC. Our results agree with other interactions and methods.

The Saturation properties of Nuclear Matter Using Different Three-Body Force at zero and finite temperature

We have used the three-body force (3BF) to modify the two body forces to achieve the empirical saturation points as well as study the ground state properties for symmetric nuclear matter using the Brueckner-Hartree-Fock approximation (BHF) with the Argonne AV18 potential at zero and finite temperature. Besides the energy per nucleon (E/A) as a function of nuclear density ρ is calculated. Further, the correction of the two-body dependent potential (correction 1) is added to shift and improve the saturation properties of the nuclear matter from ρ_o=0.265 〖fm〗^(-3) to ρ_o=0.149 〖fm〗^(-3) at E/A = -16.142 MeV towards to the empirical saturation point ρ_o=0.16 〖fm〗^(-3). In addition, the pressure p for symmetric nuclear matter for zero-temperature T=0 as a function of density ρ/ρ_o using the Argonne AV18 potential is calculated revealing good agreement between our calculations and the experimental data. On other hand, more calculations for the pressure are added at different energies T= 4, 8, 12, 18 and 20 MeV. Also, the level-density parameter as a function of density ρ is calculated for the BHF approach. Moreover, the internal energy F for the symmetric nuclear matter as a function of density ρ using the Argonne AV18 potential for continuous choice at T= 4, 8, 12, 18 and 20 MeV for the BHF with and without 3BF is calculated.

LOCV calculation for nuclear and neutron matter with the Nijmegen potential

The lowest order constrained variational (LOCV) formalism is formulated for the Nijmegen soft-core potential, which is fitted by the proton-proton (pp) scattering phase shift. The calculations are performed for the equation of state (EOS) of both nuclear and neutron matter. The state-dependent correlation functions are calculated by the minimization of two-body cluster energy, and the resulting Euler Lagrange equations are solved for this kind of potential. It is shown that LOCV calculations can work with this kind of interaction as well as other interactions in configuration space. The state-dependent correlation functions are calculated by minimization of two-body cluster energy for each channel with various JLSTMT, by using Nijmegen interaction. The correlation functions are compared with those coming from UV14 interaction in LOCV formalism. It is shown that unlike UV14, AV14, and AV18 potentials, the binding energy obtained from Nijmegen in the LOCV framework is −16.81 MeV that is close to the experimental value. Finally, it is recognized our LOCV results with Nijmegen interaction are similar to calculations with different interactions and different many-body methods.

Role of relativistic effects and three-body forces in nuclear matter properties

The role of three-body force (TBF) and the relativistic corrections (RC) on the equations of state of nuclear matter and $\ensuremath{\beta}$-stable matter (BSM) within the relativistic lowest-order constrained variation (RLOCV) approach are studied. The AV14 potential and its relativistic version $({\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{v}}_{14})$ as well as the AV18 potential are considered as the bare two-body potentials by employing the nuclear many-body Hamiltonian. It is shown that by using ${\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{v}}_{14}$, all properties of cold nuclear matter can be correctly reproduced if TBF is used in RLOCV framework. The energy and proton abundance of BSM are calculated for a wide range of baryon number densities, which are of interest in astrophysics. It is also shown that by adding RC or TBF to our calculations, the maximum proton abundance is pushed toward lower densities. Furthermore, the particle number densities decrease by including RC and increase when TBF is added to the interactions. The opposite behaviors for the role TBF and RC on saturation properties of nuclear matter as well as proton number densities of nuclear $\ensuremath{\beta}$-stable matter are found. It is also shown that the effects of three-body forces are much larger than those of relativistic corrections.

Role of nuclear correlations and kinematic effects on neutrino emission from the modified Urca processes

The neutrino emissivity from the proton branch of the modified Urca process is calculated. Angular integrations in momentum space are performed numerically without recourse to widely used, but unjustified in this specific case, approximations. To deal with nuclear correlation effects, the independent-pair approximation for nucleon quasiparticles is assumed. The realistic nuclear correlation effects are extracted from a modified extended version of the lowest-order constrained variational method in asymmetric nuclear matter in $\ensuremath{\beta}$ equilibrium with electrons and muons that allows for three-body nucleon interactions and fits all semiempirical saturation parameters of nuclear matter quite well. Two-body nucleon interaction is modeled by a realistic Argonne AV18 potential and the three-body potential used is a phenomenological Urbana UIX, generalizing parametrization of its component strengths in a manner suitable for application in asymmetric nuclear matter. Limiting to the two-body forces only, we find that, at fixed temperature, neutrino emissivity is a (weakly) decreasing function of density. This is also the case for the neutron branch of the modified Urca process analyzed by us in a recent paper. Inclusion of the modified three-body force effects changes this behavior. Quantitatively the value of the emissivity at each density increases and qualitatively the overall effect of the modified three-body force addition is such that dependence on density becomes weak in a density range from ${n}_{0}$ to $3.5{n}_{0}$. An updated version of neutron branch results obtained using our modified three-body force model is also presented. This is done using exact treatment of the angular integrations of nuclear transition rate in momentum space.

LOCV calculation of the equations of state and properties of rapidly rotating neutron stars

In this paper, we have investigated the structural properties of rotating neutron stars using the numerical RNS code and equations of state which have been calculated within the lowest order constrained variational (LOCV) approach. In order to calculate the equation of state of nuclear matter, we have used UV14 +TNI and AV18 potentials. We have computed the maximum mass of the neutron star and the corresponding equatorial radius at different angular velocities. We have also computed the structural properties of Keplerian rotating neutron stars for the maximum mass configuration, MK, RK, fK and .

Equation of state of asymmetric nuclear matter using re-projected nucleon–nucleon potentials

In this paper, we have calculated the equation of state of asymmetric nuclear matter using the lowest order constrained variational approach and Argonne family potentials with and without three-nucleon interaction (TNI) contribution. In particular, we have used the AV18 potential and the re-projected potentials, AV8′, and AV6′. We have also calculated the saturation properties of symmetric nuclear matter, and the nuclear symmetry energy using AV18+TNI, AV8′+TNI and AV6′+TNI potentials. The inclusion of TNI has modified the agreement with experiment. We have also made a comparison between our results and those of other many-body calculations.

Expansion of Magnetic Neutron Stars in an Energy (in)Dependent Spacetime

Abstract Regarding the strong magnetic field of neutron stars and the high-energy regime scenario that is based on the high-curvature region near the compact objects, one is motivated to study magnetic neutron stars in an energy-dependent spacetime. In this paper, we show that such a strong magnetic field and energy dependency of spacetime have considerable effects on the properties of neutron stars. We examine the variations of maximum mass and related radius, Schwarzschild radius, average density, gravitational redshift, Kretschmann scalar, and Buchdahl theorem due to the magnetic field and energy dependency of the metric. First, it will be shown that the maximum mass and radius of neutron stars are increasing functions of the magnetic field, while average density, redshift, strength of gravity, and Kretschmann scalar are decreasing functions of it. These results are due to a repulsive-like force behavior for the magnetic field. Next, the effects of gravity’s rainbow will be studied, and it will be shown that by increasing the rainbow function, the neutron stars could enjoy an expansion in their structures. Then, we obtain a new relation for the upper mass limit of a static spherical neutron star with uniform density in gravity’s rainbow (Buchdahl limit) in which such an upper limit is modified as . In addition, stability and energy conditions for the equation of state of neutron star matter are investigated, and a comparison with empirical results is done. It is notable that the numerical study in this paper is conducted by using the lowest-order constrained variational approach in the presence of a magnetic field employing AV 18 potential.

Comparison of nuclear Hamiltonians using spectral function sum rules

Background: The energy weighted sum rules of the single-particle spectral functions provide a quantitative understanding of the fragmentation of nuclear states due to short-range and tensor correlations. Purpose: The aim of this paper is to compare on a quantitative basis the single-particle spectral function generated by different nuclear hamiltonians in symmetric nuclear matter using the first three energy-weighted moments. Method: The spectral functions are calculated in the framework of the self-consistent Green's function approach at finite temperature within a ladder resummation scheme. We analyze the first three moments of the spectral function and connect these to the correlations induced by the interactions between the nucleons. In particular, the variance of the spectral function is directly linked to the dispersive contribution of the self-energy. The discussion is centred around two- and three-body chiral nuclear interactions, with and without renormalization, but we also provide results obtained with the traditional phase-shift-equivalent CD-Bonn and Av18 potentials. Results: The variance of the spectral function is particularly sensitive to the short-range structure of the force, with hard-core interactions providing large variances. Chiral forces yield variances which are an order of magnitude smaller and, when tamed using the similarity renormalization group, the variance reduces significantly and in proportion to the renormalization scale. The presence of three-body forces does not substantially affect the results. Conclusions: The first three moments of the spectral function are useful tools in analysing the importance of correlations in nuclear ground states. In particular, the second-order moment provides a direct insight into dispersive contributions to the self-energy and its value is indicative of the fragmentation of single-particle states.

Neutron stars structure in the context of massive gravity

Motivated by the recent interests in spin−2 massive gravitons, we study the structure of neutron star in the context of massive gravity. The modifications of TOV equation in the presence of massive gravity are explored in 4 and higher dimensions. Next, by considering the modern equation of state for the neutron star matter (which is extracted by the lowest order constrained variational (LOCV) method with the AV18 potential), different physical properties of the neutron star (such as Le Chatelier's principle, stability and energy conditions) are investigated. It is shown that consideration of the massive gravity has specific contributions into the structure of neutron star and introduces new prescriptions for the massive astrophysical objects. The mass-radius relation is examined and the effects of massive gravity on the Schwarzschild radius, average density, compactness, gravitational redshift and dynamical stability are studied. Finally, a relation between mass and radius of neutron star versus the Planck mass is extracted.

Coarse-grained short-range correlations

We develop a scheme to take into account the effects of short-range nucleon-nucleon correlations in the nucleon-pair wave function by solving the Bethe-Goldstone equation for a coarse grained delta shell potential in S-wave configuration. The S-wave delta shell potential has been adjusted to reproduce the $^1$S$_0$ phase shifts of the AV18 potential for this partial wave up to 2 GeV in the laboratory kinetic energy. We show that a coarse grained potential can describe the high momentum tail of the back-to-back correlated pairs and the $G$-matrix in momentum space. We discuss the easiness and robustness of the calculation in coordinate space and the future improvements and utilities of this model. This work suggests the possibility of using perturbation theory for describing the short-range correlations, and related to this, to substitute the $G$-matrix by an appropriate coarse-grained potential.

Muon capture onH3

The muon capture on 3H leading to muonic neutrino and three neutrons in the final state is studied under full inclusion of final state interactions. Predictions for the three-body break-up of 3H are calculated with the AV18 potential, augmented by the Urbana IX three-nucleon force. Our results are based on the single nucleon weak current operator comprising the dominant relativistic corrections. This work is a natural extension of our investigations of the muon capture on 3He leading to 3H or n+d or n+n+p and muonic neutrino in the final state, presented in Phys. Rev. C90, 024001 (2014).

Nuclear correlations and neutrino emissivity from the neutron branch of the modified Urca process

The neutrino emissivity from the neutron branch of the modified Urca process is calculated. The nuclear correlation effects are taken into account by employing the correlation functions extracted from the lowest-order constrained variational (LOCV) method applied to asymmetric nuclear matter. Two-body nucleon interaction is modeled by a realistic Argonne AV18 potential. In order to get consistency with semiempirical saturation parameters of nuclear matter and the existence of $2{M}_{\ensuremath{\bigodot}}$ pulsars, we add a phenomenological Urbana UIX three-body potential to the nucleon Hamiltonian and apply a newly formulated version of the LOCV method that allows for three-body nucleon interactions. We find that at fixed temperature neutrino emissivity is a (weakly) decreasing function of density, due to quenching of the contribution from tensor correlations with increasing density. This is in variance with all previous works. We also find that three-body forces allow for the opening of the direct Urca process at nucleon density $0.3\phantom{\rule{0.28em}{0ex}}{\mathrm{fm}}^{\ensuremath{-}3}$.

Studies of three-nucleon systems with improved chiral forces

Recently developed chiral two-nucleon (2N) potentials are applied to various processes in three-nucleon (3N) systems within the approach based on Faddeev equations. The predictions for the cross sections in elastic nucleon-deuteron (Nd) scattering and for radiative proton-deuteron (pd) capture are similar to results based on the AV18 potential. The very good convergence with respect to the chiral expansion and a weak dependence on a regularization parameter are observed. This gives hope that the Hamiltonian combining these 2N potentials with consistent 3N forces will become an important tool to study nuclear structure and processes.

Break-up channels in muon capture on3He

The μ − + 2 H → νμ + n + n, μ − + 3 He → νμ + 3 H, μ − + 3 He → νμ + n + d ,a ndμ − + 3 He → νμ + n + n + p capture reactions are studied with various realistic potentials under full inclusion offinal-state interactions. Our results for the two- and three-body break-up of 3 He are calculated with a variety of nucleon-nucleon potentials, among which is the AV18 potential, augmented by the Urbana IX three-nucleon potential. Most of our results are based on the single-nucleon weak-current operator. As a first step, we tested our calculation in the case of the μ − + 2 H → νμ + n + n and μ − + 3 He → νμ + 3 H reactions, for which theoretical predictions obtained in a comparable framework are available. Additionally, we have been able to obtain for the first time a realistic estimate for the total rates of the muon capture reactions on 3 He in the break-up channels: 544 s −1 and 154 s −1 for the n + d and n + n + p channels, respectively. Our results are compared with the most recent experimental data, finding a rough agreement for the total capture rates, but failing to reproduce the differential capture rates.