Workshop on the sign problem in QCD and beyond

Session

Wednesday morning (Uwe-Jens Wiese mini-symposium part 1)

22 Jan 2025, 08:30

Lecture Hall 099 (ExWi Building) (University of Bern)

11. The Ising Model on a Curved Manifold -- The Affine Conjecture

Richard Brower (Boston University)

22/01/2025, 08:30

talk

A formulation of lattice field theory (LFT) for curved manifolds uses the Regge's triangulated (simplicial) manifold for the Einstein Hilbert action that solves the equation of motion (EOM) for classical GR in the continuum. For the metric field, $g_{\mu \nu}(x)$, this is piece-wise constant finite element method (FEM) which applies equally to the classical field PDEs. But quantizing lattice...

10. How many states are gauge invariant?

Alessandro Mariani

22/01/2025, 09:15

talk

Hamiltonian methods, such as quantum simulation, are often advocated as a long term solution to some sign problems. In this context, it is more natural to work with a finite-dimensional Hilbert space; as such, a truncation method must be employed. Moreover, for gauge theories, only a small subsets of states are gauge invariant and therefore physical. In this context, both for technical reasons...

35. Sign-blessed thermodynamics of interacting fermions

Nikolay Prokofiev (University of Massachusetts Amherst)

22/01/2025, 10:45

talk

I will review several key features associated with the conventional sign problem and argue that for regular interacting fermionic systems none of them applies if the calculation is done with the help of Feynman diagrams. The diagrammatic approach generically solves the computational complexity problem and can be used for obtaining numerical solutions for interacting fermions. I will illustrate...

30. Homotopic Action: A Pathway to Convergent Diagrammatic Theories

Boris Svistunov (University of Massachusetts Amherst)

22/01/2025, 11:30

talk

The major obstacle preventing Feynman diagrammatic expansions from accurately solving many-fermion systems in strongly correlated regimes is the series slow convergence or divergence problem. Several techniques have been proposed to address this issue: series resummation by conformal mapping, changing the nature of the starting point of the expansion by shifted action tools, and applying the...