Münster 2017 – scientific programme

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HK: Fachverband Physik der Hadronen und Kerne

HK 23: Nuclear Astrophysics II

HK 23.3: Talk

Tuesday, March 28, 2017, 14:45–15:00, F 33

Expansion of the equation of state of neutron-rich nuclear matter from χEFT beyond quadratic order — •Susanne Strohmeier and Norbert Kaiser — Technische Universität München

Based on chiral effective field theory, the equation of state of neutron-rich nuclear matter is investigated systematically. The contributing diagrams up to three-loop order include one- and two-pion exchange together with three-body terms arising from virtual Δ(1232)-isobar excitations. The expansion of the energy per particle in the proton fraction δ for the nuclear many-body system with neutron density ρ_n= k_f³ (1−δ)/3 π² and proton density ρ_p= k_f³ δ/3 π² is performed analytically up to quadratic order: Ē(k_f,δ) = Ē_n(k_f) + δ B₁(k_f) +δ^5/3 B_5/3 (k_f) + δ ² B₂ (k_f) + … . Yet higher orders in the δ-expansion are necessary for a reasonable description of the equation of state for proton fractions above 20%. The evaluation of a S-wave contact interaction to second order establishes a non-analytical δ^7/3lnδ-term. The higher order coefficients of the expansion are determined by a least-squares fit. With terms up to order δ^8/3 a good description is obtained from pure neutron matter (δ=0) up to symmetric nuclear matter (δ=0.5).
Work supported in part by DFG and NSFC (CRC110).