Title: Pluri-lagrangian structure as integrability of variational systems.

Prof. Suris, Yuri, Technische Universität Berlin, Germany, 2017-04-11, 4:50-5:50pm, Hill 525, please note the special time and room. This is the second talk on April 11.

Abstract: We propose a notion of a pluri-Lagrangian problem, which should be understood as an analog of multi-dimensional consistency for variational systems. This is a development along the line of research of discrete integrable Lagrangian systems initiated in 2009 by Lobb and Nijhoff, however having its more remote roots in the theory of pluriharmonic functions, in the Z-invariant models of statistical mechanics and their quasiclassical limit, as well as in the theory of variational symmetries going back to Noether. We discuss main features of pluri-Lagrangian systems in dimensions 1 and 2, both continuous and discrete, along with the relations of this novel structure to more standard notions of integrability.