Dirks, Andreas Eckstein, Martin Pruschke, Thomas Werner, Philipp 2013-02-21 We investigate the possibility to assist the numerically ill-posed calculation of spectral properties of interacting quantum systems in thermal equilibrium by extending the imaginary-time simulation to a finite Schwinger-Keldysh contour. The effect of this extension is tested within the standard maximum entropy approach to analytic continuation. We find that the inclusion of real-time data improves the resolution of structures at high energy, while the imaginary-time data are needed to correctly reproduce low-frequency features such as quasiparticle peaks. As a nonequilibrium application, we consider the calculation of time-dependent spectral functions from retarded Green function data on a finite time interval, and compare the maximum entropy approach to direct Fourier transformation and a method based on Padé approximants. application/pdf https://folia.unifr.ch/global/documents/303058 https://folia.unifr.ch/documents/303058/files/wer_esp.pdf eng info:eu-repo/semantics/altIdentifier/doi/10.1103/PhysRevE.87.023305 info:eu-repo/semantics/openAccess License undefined Physical Review E. - 2013, vol. 87, no. 2, p. 023305 info:eu-repo/classification/udc/53 Extracting spectral properties from Keldysh Green functions http://purl.org/coar/resource_type/c_6501