Variational principles for exclusive and inclusive cross sections
Pierre Amiot, BERTRAND G. GIRAUD, M.A. Nagarajan · Physical Review C · 1984
Density matrices and dyadic operators are systematically introduced in the definition of a $T$-matrix element and the square modulus of that element. This use of the density matrices and dyadic operators provides two new variational functionals in addition to the Kohn-Schwinger type functional. An equivalence between the evaluation of the inverse of an operator and a diagonalization procedure for practical calculations is also established.