MSc Thesis Defence: Quantum Monte Carlo for Nuclear Physics: On and Off the Lattice

MSc Candidate

Ryan Curry

Abstract

We  investigate  the  nuclear  many-body  problem  through  two  distinct  projects.  In  the  first,  we  develop  a  novel  method  for  calculating  the  second-order  perturbation  theory  correction  to  the  ground state energy of a nuclear-many system in a continuum Quantum Monte Carlo calculation. Second-order (and higher) perturbative corrections are very difficult to calculate in most ab initio many-body  methods  since  they  are  usually  concerned  with  calculating  only  the  ground  state  energy. By introducing a new method that maps the calculation of the second-order correction to an evolution in imaginary time using Diffusion Monte Carlo, we are able to calculate these terms for the first time in a continuum nuclear context. We complete benchmarking calculations in the two-body sector,  as  well  as  for  interactions  that  break  charge  independence  in  the  nuclear  Hamiltonian. We then employ our new method to investigate the many-body perturbativeness of modern  nuclear  interactions  derived  from  chiral  effective  field  theory.  We  find  that  in  certain  regimes the interactions are not entirely perturbative, which could have important implications for nuclear  physics.  In  the  second  project,  we  change  tactics  and  approach  the  nuclear  many-body problem within a lattice formalism. We apply a lattice based Auxiliary Field Quantum Monte Carlo approach that is used widely for the study of condensed matter systems, and modify it in order to study nuclear systems. This work serves as the foundation for building an ongoing nuclear physics research program using lattice quantum Monte Carlo.

Examination Committee

• Dr. Eric Poisson, Chair
• Dr: Alexandros Gezerlis, Advisor
• Dr. Paul Garrett, Advisory Committee
• Dr. Robert Wickham, Graduate Faculty