In-Medium Similarity Renormalization Group with NN and 3N Interactions

The primary use of the Similarity Renormalization Group (SRG) in nuclear physics is the derivation of effective interactions from underlying realistic vacuum NN and 3N interactions, which have a greatly improved convergence behavior in nuclear many-body calculations. The SRG flow equation formalism has much wider applications, though. In the In-Medium SRG the Hamiltonian is evolved directly in the A-body system (i.e., at finite density). By a suitable choice of generator the ground state is decoupled from particle-hole excitations, and the IMSRG can be considered an ab initio technique for solving the many-body problem. The modest computational effort makes calculations for medium-mass and heavy nuclei feasible. I will give a brief overview of the method, present results for closed-shell nuclei with NN and 3N interactions, and discuss the progress in our effort to generalize the IM-SRG formalism for arbitrary reference states, with the aim of extending our calculations to open-shell nuclei. \\[4pt] References: K. Tsukiyama, S. Bogner, and A. Schwenk, Phys. Rev. Lett. 106, 222502 (2011)\\[0pt] S. Bogner, R. Furnstahl, and A. Schwenk, Prog. Part. Nucl. Phys. 65, 94 (2010)