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## SIGN 2021

#### CECAM-ISR

#### Organisers

The workshop will be dedicated to the sign problem in quantum mechanics and quantum field theory. This will be the eighth workshop in a series held every 1-2 years since 2009.

The sign problem is a computational challenge for simulations of various physical problems. It usually occurs in systems that include fermions and in particular in supersymmetric systems, in systems with non-zero chemical potential, in systems with frustration and with topological terms, in the simulation of systems in Lorentzian signature, as well as in other cases. In particular, the problem arises in the study of QCD at finite baryon density. Hence, it is relevant to our understanding of problems in nuclear physics, high energy physics, and astrophysics.

The origin of the sign problem can be traced to large cancellations among terms that lead to a result much smaller in absolute value. While this might seem like a simple nuisance it was argued that in particular cases the sign problem is an NP-hard problem. Hence, it is not expected that a complete solution would be found. Nonetheless, various approaches in particular cases have led to significant improvement of our computational abilities. Among these approaches one can mention the Complex Langevin Method, Lefschetz Thimbles and other methods based on contour deformations and analytic continuation. Researchers in the field are also attempting the development of Machine Learning methods and of Quantum Algorithms.

The main audience of the workshop is that of physicists working on lattice field theory, but we hope to have also physicists working on related condensed matter problems as well as computer science researchers.

## References

**Israel**

Anatoly Golberg (Holon Institute of Technology) - Organiser

Michael Kroyter (Holon Institute of Technology) - Organiser

Benjamin Svetitsky (Tel Aviv University) - Organiser