23 citations · 23 across the 1 of their papers we have counts for
4 papers
Energy-level diagrams and their contribution to fifth-order Raman and second-order infrared responses: Distinction between relaxation mechanisms by two-dimensional spectroscopy
Ko Okumura, Yoshitaka Tanimura
We develop a Feynman rule for energy-level diagrams emphasizing their connections to the double-sided Feynman diagrams and physical processes in the Liouville space. Thereby we com…
Effective actions of local composite operators --- case of theory, itinerant electron model, and QED
K. Okumura
A compact graph rule for the effective action of a local composite operator is given in this paper. This long-standing problem of obtaining in this case is solved dir…
The supergroup U(M/N) with regard to electronic Hamiltonians
Ko Okumura
We study the U(M/N) supergroup keeping in mind its connection with electronic Hamiltonians. It is explicitly shown that the generators of the supergroup U(N/N) can be expressed by…
Various condensed matter Hamiltonians in terms of U(2/2) operators and their symmetry structures
Ko Okumura
We rewrite various lattice Hamiltonian in condensed matter physics in terms of U(2/2) operators that we introduce. In this representation the symmetry structure of the models becom…