James P. Vary (born Savanna, Illinois, May 1943) is an American theoretical physicist and professor at the Iowa State University, specializing in nuclear theory with an emphasis on "ab initio" solutions of quantum many-particle systems and light-front quantum field theory.
He leads the nuclear theory group at Iowa State University[1] supported by the US Department of Energy (DOE).
Vary is known for his work in theoretical nuclear physics with an emphasis on effective Hamiltonians for strongly interacting systems and for developing new ab initio approaches to the microscopic structure of nuclei for solving the fundamental nuclear many-body problems as well as problems in light-front quantum field theory including Quantum Chromodynamics.
His work employs similarity transformations, which seek to decouple the “low-energy” degrees of freedom from the “high-energy” degrees of freedom related to the renormalization group approaches in quantum field theory and the non-perturbative Hamiltonian renormalization methods.
He also works on the strong field (non-perturbative) scattering problems with a time-dependent extension to BLFQ (tBLFQ).