Let $G$ be a finite group and let $H_G$ denote the $G$-harmonic polynomials. What is the structure of $H_G$ as a $G$-module? Is it isomorphic to the regular representation?
2 Answers
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In fact $H_G$ is isomorphic to the regular representation if and only if G is generated by (pseudo)-reflections. This is a theorem of Steinberg. A good reference for this is the manuscript "Orbit Harmonics and Graded Representations" by Haiman and Garsia.