In-Medium Similarity Renormalization Group for Open-Shell Nuclei
  We present a nonperturbative derivation of effective valence-shell Hamiltonians in the framework of the recently developed in-medium similarity renormalization group (IM-SRG). As a first application, we calculate the spectra of $p$- and $sd$-shell nuclei, $^6$Li and $^{18}$O, based on evolved chiral nucleon-nucleon interactions. For $^6$Li, the spectrum is in very good agreement with ab-initio results. For $^{18}$O, the IM-SRG provides a new method for the shell model to systematically go beyond effective interaction techniques based on diagrammatic expansions. 
K. Tsukiyama, S. K. Bogner, A. Schwenk
nucl-th cond-mat.other hep-ph