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SCGP Weekly Talk by Matthias Staudacher

Matthias Staudacher

Title: Bethe Ansatz for Yangian Invariants: Towards Super Yang-Mills Scattering Amplitudes
Speaker: Matthias Staudacher
Date: Friday, December 6, 2013
Time: 1:00pm – 2:00pm
Place: Lecture Hall 102, Simons Center



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Abstract: We propose that Baxter’s Z-invariant six-vertex model at the rational gl(2) point on a planar but in general not rectangular lattice provides a way to study Yangian invariants. These are introduced as eigenfunctions of certain monodromies of an auxiliary inhomogeneous spin chain. As a consequence they are special solutions to the eigenvalue problem of the associated transfer matrix. Excitingly, this allows to construct them using Bethe ansatz techniques. Conceptually, our construction generalizes to general (super) Lie alge- bras and general representations. Here we present the explicit form of the basic building blocks of the invariants for totally symmetric, finite-dimensional representations of gl(n) in terms of oscillator algebras. In particular, we discuss invariants of three- and four-site monodromies that can be understood respectively as intertwiners of the bootstrap and Yang-Baxter equation. We state a set of functional relations significant for these representations of the Yangian and discuss their solutions in terms of Bethe roots. In addition, it is shown that the basic building blocks can be expressed analogously to Grassmannian integrals. These aspects are closely related to a recent on-shell formulation of scattering amplitudes in N = 4 super Yang-Mills theory.