The seminar "Time Correlation function Approach for Optical, X-ray and Vibrational Response", will focus on real-time approaches for calculations of excited states and response functions. In contrast to conventional methods in frequency space, real-time approaches approaches are of growing interest both experimentally and theoretically.  Our approach is based on the behavior of time corelation functions which are the time-domain analogs of measurable spectra. For example, the density-density correlation function corresponds to optical response and the displacement-displacement correlation function to vibrational spectra. As a final example, the approach will be used to calculate  the core-electron Green's function within the cumulant model for XPS and XAS.  

This work is part of a continued interaction with the ETSF, and in particular the LSI Theoretical Spectroscopy group at Ecole Polytechnique.