Nuclear structure calculations in the UCOM framework

The Unitarity Correlation Operator Method and the Similarity Renormalization Group are powerful techniques for the derivation of effective interactions from current realistic NN potentials like Argonne AV18 or the chiral N3LO forces, which are suitable for a wide range of many-body methods, including Hartree-Fock(-Bogolyubov) (HF/HFB), Many-Body Perturbation Theory, RPA and quasi-particle RPA. We discuss nuclear structure calculations based on these interactions, including three-body forces via contact terms or corresponding density-dependent two-body forces. We primarily focus on open-shell nuclei and the treatment of pairing phenomena in an HFB framework, discussing pairing gaps in isotopic and isotonic chains. The systematic connection to the free NN problem offers new insight into open questions regarding nuclear superfluidity, e.g., the importance of surface vibrations. The impact of pairing correlations on collective excitations is addressed in a QRPA framework, and tentative results are shown, for instance, for the supposed Pygmy dipole resonances in the tin isotopes.