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Invariants of coinvariant algebras

  • Larry Smith
Published/Copyright: May 29, 2014

Abstract

Let ρ:G GL (n,𝔽) be a representation of a finite group G over the field 𝔽 and let HG be a subgroup of G. Form the algebra of polynomial functions 𝔽[V] on the representation space V=𝔽n of ρ. The action of G on V extends to 𝔽[V] and we denote by 𝔽[V]G the invariant algebra; namely, the subalgebra of G-invariant forms. The coinvariant algebra of ρ is the quotient algebra 𝔽[V]G=𝔽[V]/𝔥(G) where the Hilbert ideal𝔥(G) of G (or better put, of ρ) is the ideal of 𝔽[V] generated by all the homogeneous G-invariant forms of strictly positive degree. The group H acts on 𝔽[V]G and the subject of this manuscript is the algebra (𝔽[V]G)H of H-invariants of 𝔽[V]G.

Received: 2013-9-17
Revised: 2014-3-17
Published Online: 2014-5-29
Published in Print: 2015-11-1

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