Improved nuclear matter calculations from chiral low-momentum interactions

We present nuclear matter calculations based on low-momentum interactions derived from chiral effective field theory potentials. The current calculations use an improved treatment of the three-nucleon force (3NF) contribution that includes a corrected combinatorial factor beyond Hartree-Fock that was omitted in previous nuclear matter calculations. We find realistic saturation properties using parameters fit only to few-body data, but with larger uncertainty estimates from cutoff dependence and the 3NF parametrization than in previous calculations.

Figure 1

Nuclear matter energy per particle versus Fermi momentum $k_{\mathrm{F}}$ at the Hartree-Fock level (left) and including second-order (middle) and third-order particle-particle/hole-hole contributions (right), based on evolved ${\mathrm{N}}^3$LO NN potentials and 3NF fit to $E_{{}^3\mathrm{H}}$ and $r_{{}^4\mathrm{He}}$. Theoretical uncertainties are estimated by the NN (lines)/3N (band) cutoff variations.

Figure 2

Nuclear matter energy of Fig. 1 at the third-order level compared to NN-only results for two representative NN cutoffs and a fixed 3N cutoff.

Figure 3

Nuclear matter NN-only results for different chiral ${\mathrm{N}}^3$LO potentials (EM [19] and EGM [30]). The upper panel shows the third-order results for $V_{\mathrm{low}\hspace{0.5em}k}$-evolved interactions at $\Lambda =2.0\hspace{0.5em}{\mathrm{fm}}^{-1}$ (solid lines) and Brueckner-Hartree-Fock results for the two unevolved chiral potentials that provide the lowest and highest energies (dashed lines), EGM 600/700 MeV and EM 600 MeV. The lower panel shows the maximal spread of the energy results at these two cutoff scales $\Lambda$ for $V_{\mathrm{low}\hspace{0.5em}k}$ and $\lambda$ for SRG-evolved NN interactions.

Figure 4

Nuclear matter energy at the third-order level comparing low-momentum $V_{\mathrm{low}\hspace{0.5em}k}$ with SRG-evolved chiral NN interactions for 3NF with different EM/PWA/EGM $c_i$ values used (see text).