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The Plefka expansion is a method for approximately analyzing complicated probabilistic systems such as those consisting of many interacting particles. In principle, it consists of an expansion in the interaction strength around the non-interacting case. Important applications are the calculation of expectation values of observables as well as the problem of statistical inference encountered for example in the inverse Ising problem. In order to assess the applicability of the expansion to a specific system, it is important to know the radius of convergence. Unfortunately, this radius is only known for very few systems, the Sherrington-Kirkpatrick model of a spin glass being the most prominent one. This talk will introduce the general concept of the Plefka expansion applied to the Ising model as well as explicitly derive the radius of convergence for the 1D ferromagnet.

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Simon Dettmer, University of Cologne
Conference Room THP
Contact: not specified