Bogoliubov many-body perturbation theory under constraint

In order to solve the A-body Schrödinger equation both accurately and efficiently for open-shell nuclei, a novel many-body method coined as Bogoliubov perturbation theory (BMBPT) was recently formalized applied at low orders. Based on breaking of U(1) symmetry associated with particle-number conservation, this must operate under constraint that average number particles is self-consistently adjusted each perturbative order. The corresponding formalism presently detailed goal characterize behaviour Taylor series. BMBPT is, thus, investigated numerically up high orders price restricting oneself small, i.e. schematic, portion Fock space. While low-order results only differ by 2?3% from those obtained via configuration interaction (CI) diagonalization, series shown eventually diverge. application resummation eigenvector continuation further increases accuracy when built corrections quickly converges towards CI result higher Furthermore, numerically-costly self-consistent particle adjustment procedure be safely bypassed use computationally cheap posteriori correction method. Eventually, present work validates fact calculations based an (average) deliver controlled demonstrates they can optimally complemented provide sub-percent accuracy. This approach planned become workhorse realistic ab initio nuclei in near future.