Function sequant::mbpt::bernoulli::detail::N_part

• Defined in File bernoulli.cpp

Function Documentation

ExprPtr sequant::mbpt::bernoulli::detail::N_part(const ExprPtr &expr, std::size_t cutoff, std::size_t min_rank)

Block-resolved \(N\) part ( \(O_N\) of 10.1063/1.5030344): the terms whose single residual NormalOperator is a pure excitation or pure de-excitation of rank in \([\mathtt{min\_rank},\mathtt{cutoff}]\). Applies expand_to_blocks first.

Parameters:

• expr – expression to partition

• cutoff – highest excitation/de-excitation rank in \(O_N\)

• min_rank – lowest rank \(\sigma\) carries, so 2 when singles are skipped. Below it there is no amplitude and the condition \(\bar{V}_N=0\) that justifies calling a term \(N\) does not hold.