A simple bijection between standard (n,n,n) tableaux and irreducible webs for sl_3

TL;DR

This paper introduces a simple, explicit bijection between standard Young tableaux of shape (n,n,n) and irreducible webs for sl_3, connecting combinatorial and graphical models of representation invariants.

Contribution

It provides a straightforward map matching tableaux to webs, confirms it aligns with previous recursive bijections, and extends the correspondence to include operations like rotation and shuffling.

Findings

The new map is equivalent to Khovanov-Kuperberg's recursive bijection.

Rotation of webs corresponds to jeu-de-taquin promotion on tableaux.

The paper introduces the concept of a shuffle operation on tableaux, related to web joins.

Abstract

Combinatorial spiders are a model for the invariant space of the tensor product of representations. The basic objects, webs, are certain directed planar graphs with boundary; algebraic operations on representations correspond to graph-theoretic operations on webs. Kuperberg developed spiders for rank 2 Lie algebras and sl_2. Building on a result of Kuperberg's, Khovanov-Kuperberg found a recursive algorithm giving a bijection between standard Young tableaux of shape (n,n,n) and irreducible webs for sl_3 whose boundary vertices are all sources. In this paper, we give a simple and explicit map from standard Young tableaux of shape (n,n,n) to irreducible webs for sl_3 whose boundary vertices are all sources, and show that it is the same as Khovanov-Kuperberg's map. Our construction generalizes to some webs with both sources and sinks on the boundary. Moreover, it allows us to extend the correspondence between webs and tableaux in two ways. First, we provide a short, geometric proof of Petersen-Pylyavskyy-Rhoades's recent result that rotation of webs corresponds to jeu-de-taquin promotion on (n,n,n) tableaux. Second, we define another natural operation on tableaux called a shuffle, and show that it corresponds to the join of two webs. Our main tool is an intermediary object between tableaux and webs that we call an m-diagram. The construction of m-diagrams, like many of our results, applies to shapes of tableaux other than (n,n,n).