Nuclear Seminar

Simplifying the Nuclear Many-Body Problem with Low Momentum Interactions

Dr. Scott Bogner
Ohio State University

Monday, October 2, 2006   4:00 p.m.   NSH 124
(Refreshments served prior to seminar in NSH 124)

 

Microscopic nuclear many-body calculations are complicated by strong short-range repulsion and tensor forces that necessitate highly correlated trial wave functions, nonperturbative resummations, and large basis expansions.  However, the non-perturbative nature of inter-nucleon interactions is strongly scale or resolution dependent, and can be radically softened by using the renormalization group (RG) to lower the momentum cutoff that is present in the interactions.  A consequence is that nuclear many-body problems become much more tractable at lower resolutions, resulting in calculations that are amenable to straightforward perturbative methods and simple (i.e., less correlated) variational ansätze.  Since Hartree-Fock becomes a sensible zeroth order approximation, the large arsenal of techniques developed for non-uniform electronic systems (e.g., density functional methods) become available for nuclei.  The Density Matrix Expansion (DME) of Negele and Vautherin provides a constructive framework to microscopically derive and constrain the nuclear energy density functional.  In contrast to the original work on the DME, the use of chiral effective field theory (EFT) interactions ensures that pionic effects are strongly constrained by the symmetries of QCD with consistent many-body forces.  The use of the RG-evolved interactions allows one to study how the different terms in the energy functional change with the resolution, which may be useful for formulating theoretical constraints for fitting parameters appearing in phenomenological functionals.