A survey of the Shi arrangement

In 1983, Lusztig defined a map $σ$ from affine permutations of $n$ to partitions of $n$. He conjectured that for any partition $λ$ of $n$, $σ^{-1}(λ)$ is a two-sided cell. Shi, in 1986, proved part of this conjecture. As a byproduct, he introduced the Shi arrangement of hyperplanes and found a few of its remarkable properties. The Shi arrangement has since become a central object in algebraic combinatorics. This article is intended to be a fairly gentle introduction to the Shi arrangement, intended for readers with a modest background in combinatorics, algebra, and Euclidean geometry.

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