2 papers
math-ph2022
Cutting rules and positivity in finite temperature many-body theory
Markku J. Hyrkäs, Daniel Karlsson, Robert van Leeuwen
For a given diagrammatic approximation in many-body perturbation theory it is not guaranteed that positive observables, such as the density or the spectral function, retain their p…
cond-mat.str-el2015
Computing Exact Self-Energies with Polynomial Expansion
M. Hyrkäs, D. Karlsson, R. van Leeuwen
We give details on how to calculate spectral functions and Green's functions for finite systems using the Chebyshev polynomial expansion method. We apply the method to a finite And…