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arXiv · 1210.7867

Extracting spectral properties from Keldysh Green functions

Andreas Dirks·Martin Eckstein·Thomas Pruschke·Philipp Werner
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Abstract

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 quasi-particle 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.

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Andreas Dirks, Martin Eckstein, Thomas Pruschke, Philipp Werner. 2012-10-29. Extracting spectral properties from Keldysh Green functions. https://doi.org/10.1103/physreve.87.023305

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