Mainz 2012 – wissenschaftliches Programm

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HK: Fachverband Physik der Hadronen und Kerne

HK 1: Hadronenstruktur und -spektroskopie

HK 1.6: Vortrag

Montag, 19. März 2012, 15:30–15:45, RW 1

Resummation of fermionic in-medium ladder diagrams to all orders — •Norbert Kaiser — Physik-Department, Technische Universität München

A system of fermions with a short-range interaction proportional to the scattering length a is studied at finite density. At any order aⁿ, we evaluate the complete contributions to the energy per particle Ē(k_f) arising from combined (multiple) particle-particle and hole-hole rescatterings in the medium. This novel result is achieved by decomposing the particle-hole propagator into the vacuum propagator plus a medium-insertion. The emerging series in a k_f can be summed to all orders in form of a double-integral over an arctangent function. Taking the unitary limit a→ ∞, one obtains the value ξ= 0.507 for the universal Bertsch parameter. Extensions of the resummation method by including the s-wave effective range r_s and a (spin-independent) p-wave contact interaction are presented. We perform also an exact (5-loop) calculation of a three-body contact interaction to second order.

Supported in part by BMBF, GSI, and the DFG Cluster of Excellence: Origin and Structure of the Universe.