NESSi is an open-source software package for the manipulation of nonequilibrium Green’s functions defined on the Kadanoff-Baym contour. The Green's function method in its time-dependent formulation is a versatile framework for the solution of interacting many-body problems out of equilibrium. NESSi provides classes representing the various types of Green’s functions, implements the basic operations on these functions and allows to solve the corresponding equations of motion. The library is aimed at the study of transient dynamics from an initial equilibrium state, induced by time-dependent model parameters.
Overview:
- NESSi provides tools for constructing Feynman diagram and solving equations of motion for non-equilibrium Green's functions on the Kadanoff-Baym contour
- NESSi is based on high-order quadrature rules: for N time slices, the error scales like O(N-p) with p up to 7.
- Efficient distributed-memory parallelization over reciprocal space allows large-scale calculations on extended systems.
The NESSi program package contains two major directories:
| Directory | Content |
|---|---|
| libcntr | The libcntr library. |
| examples | Example programs based on libcntr. |
More information on the directory structure and the source files can be found in the respective directories.
The full documentation, installation instructions, examples and tutorials is available here.
Please cite the following paper whenever you use parts of NESSi:
Michael Schüler, Denis Golež, Yuta Murakami, Nikolaj Bittner, Andreas Herrmann, Hugo U. R. Strand, Philipp Werner, Martin Eckstein, Computer Physics Communications 257, 107484 (2020)
This project is licensed under the MPL 2.0 License - see the LICENSE.md file for details