We compare theoretical techniques utilized for description of optical
response in molecular junctions, and their application to simulate Raman
spectroscopy in such systems. Strong and weak sides of the Hilbert vs.
Liouville space, as well as quasiparticles vs. many-body states, formulations
are discussed. Common origins of the methodologies and different approximations
utilized in different formulations are identified.Comment: 17 pages, 4 figure
