Omokuyani Udiani (MSU/FRIB)
Convergence Acceleration Using Novel Insights on the In-Medium Similarity Renormalization Group and Unitary Coupled Cluster Theory

The in-medium similarity renormalization group (IMSRG) and unitary coupled-cluster (UCC) are iterative operator diagonalization methods used to calculate observables of a nuclear many-body system with a nucleon-nucleon interaction. The IMSRG computes operators (called generators) known to be effective diagonalizers, to gradually eliminate off-diagonal components of a given hamiltonian.
In this talk, I will introduce simple perturbative arguments on how a novel generator can be constructed to accelerate the diagonalization of a nuclear hamiltonian. I will present semi-analytic expressions for such a generator. Moreover, I will present results showing the effectiveness of this generator beyond traditional 2nd order many-body perturbation theory. I will argue the power of the generator lies within its unification of UCC and IMSRG theory. Lastly, I will propose a framework for computing this generator with an embarrassingly parallel algorithm. All results presented will be for pure and symmetric nuclear matter in a finite periodic box, using at most 2-body forces from the Minnesota and chiral N2LO-Opt potential.
The ultimate aim of this work is to provide computationally efficient expressions that aid IMSRG calculations for the nuclear equation of state.