Ab-initio calculations of bound and unbound nuclei in the Berggren basis: The No Core Gamow Shell Model

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Date/Time:Thursday, 26 Sep 2013 from 4:10 pm to 5:00 pm
Location:A401 Zaffarano Hall
Contact:Prof. James Vary
Phone:515-294-8894
Channel:Nuclear Physics
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Dr. George Papadimitriou, University of Arizona

A brief overview of the nuclear many-body problem will be given, followed by a discussion of the No core Gamow shell model (NCGSM) as it applies to study selected well-bound and unbound states of helium isotopes. This method, formulated in the complex energy plane and using a complete Berggren ensemble, is appropriate for a description of bound states, resonances, and the many-body scattering states. For the diagonalization of the very large complex symmetric matrix, we apply numerical algorithms, such as the Lanczos method generalized to complex eigenvalue problems and the Density Matrix Renormalization Group (DMRG) method. The latter is a truncation algorithm and will help us explore properties of heavier systems in the NCGSM. The ab-initio NCGSM calculations start from either bare interaction or various renormalized two-body interactions such as Vlow-k. The single-particle Berggren ensemble consists of bound, resonance and non-resonant continuum states. To test the validity of our approach, we benchmarked the NCGSM results against Faddeev and Faddeev-Yakubovsky exact calculations for 3H and 4He nuclei. We also performed ab-initio NCGSM calculations for the unstable nucleus 5He and determined the ground state energy and decay width. Additionally, we are calculating microscopically overlap integrals and spectroscopic factors and we also apply our machinery to the excited states of 4He. If time permits an alternative method formulated in the complex energy plane, the Complex Scaling method, widely used in Quantum Chemistry for the determination of resonance parameters, will be introduced. Certain advantages of the approach will be discussed.