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The ALF (Algorithms for Lattice Fermions) project release 2.4. Documentation for the auxiliary-field quantum Monte Carlo code
by ALF Collaboration, F. F. Assaad, M. Bercx, F. Goth, A. Götz, J. S. Hofmann, E. Huffman, Z. Liu, F. Parisen Toldin, J. S. E. Portela, J. Schwab
Submission summary
| Authors (as registered SciPost users): | Fakher F. Assaad · Johannes Stephan Hofmann · Jefferson Portela |
| Submission information | |
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| Preprint Link: | https://arxiv.org/abs/2012.11914v8 (pdf) |
| Code repository: | https://git.physik.uni-wuerzburg.de/ALF/ALF |
| Code version: | 2.4 |
| Code license: | GPLv3 + additional terms |
| Date accepted: | Oct. 10, 2025 |
| Date submitted: | Oct. 1, 2025, 9:37 a.m. |
| Submitted by: | Jefferson Portela |
| Submitted to: | SciPost Physics Codebases |
| Follows up on: |
| Ontological classification | |
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| Academic field: | Physics |
| Specialties: |
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| Approach: | Computational |
Abstract
The Algorithms for Lattice Fermions package provides a general code for the finite-temperature and projective auxiliary-field quantum Monte Carlo algorithm. The code is engineered to be able to simulate any model that can be written in terms of sums of single-body operators, of squares of single-body operators and single-body operators coupled to a bosonic field with given dynamics. The package includes five pre-defined model classes: SU(N) Kondo, SU(N) Hubbard, SU(N) t-V and SU(N) models with long range Coulomb repulsion on honeycomb, square and N-leg lattices, as well as $Z_2$ unconstrained lattice gauge theories coupled to fermionic and $Z_2$ matter. An implementation of the stochastic Maximum Entropy method is also provided. One can download the code from our Git instance at https://git.physik.uni-wuerzburg.de/ALF/ALF/-/tree/ALF-2.4 and sign in to file issues.
Author comments upon resubmission
The method we use is correct and follows precisely the seminal work of T. Grover. Although there are no conceptual errors, it is known that the method proposed by T. Grover suffers from fat tails and spikes in the measurements in the strong coupling regime. In the revised version of the manuscript, we comment on this aspect of the Grover approach for the calculation of the Renyi entropies. It is however a very useful approach for small subsystems in the weak to intermediate coupling regime.
In the meantime, there has been major progress in the calculation of the Renyi entropy. In particular a fermion generalization of the incremental approach has been proposed. In the revised version of the manuscript, we clearly mention the limitations of the implemented calculation of the Renyi entropies. It is beyond the scope of this version to implement the incremental method.
We would also like to thank the referee for pointing out typos in the manuscript.
List of changes
- Below Eq. 193. We have added a word of caution for the use of the Grover method to compute Renyi entropies.
- Again below Eq. 193. We have added Refs. 146 and 147. Both references document recent progress in the calculation of the Renyi entropy.
- We have attempted to catch all the typos.
Published as SciPost Phys. Codebases 1-v2.4 (2025) , SciPost Phys. Codebases 1-r2.4 (2025)