Frankfurt 2014 – scientific programme

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HK: Fachverband Physik der Hadronen und Kerne

HK 10: Struktur und Dynamik von Kernen

HK 10.5: Talk

Monday, March 17, 2014, 18:00–18:15, HZ 4

Chiral four-body interactions in nuclear matter — •Kaiser Norbert — Physik-Department, Technische Universität München

The effects of chiral four-nucleon interactions in nuclear and neutron matter are studied. The leading-order terms arising from pion-exchange in combination with the chiral 4π-vertex and the chiral NN3π-vertex are found to be very small. The contributions of reducible four-nucleon interactions generated by the method of unitary transformations are included as well. We consider also the four-nucleon interaction induced by pion-exchange and twofold Δ-isobar excitation of nucleons. For most of the closed four-loop diagrams the occurring integrals over four Fermi spheres can either be solved analytically or reduced to one- or two-parameter integrals. After summing the individually large contributions from 3-ring, 2-ring and 1-ring diagrams of alternating signs, one obtains at nuclear matter saturation density ρ₀=0.16 fm⁻³ a moderate contribution of about 2 MeV to the energy per particle. The curve Ē(ρ) rises rapidly with density, approximately as ρ³. In pure neutron matter the chiral four-body interactions lead to a repulsive contribution that is about half as strong.