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Rationality of the Hilbert series of Hopf-invariants of free algebras (1105.5364v1)
Published 26 May 2011 in math.RA
Abstract: It is shown that the subalgebra of invariants of a free associative algebra of finite rank under a linear action of a semisimple Hopf algebra has a rational Hilbert series with respect to the usual degree function, whenever the ground field has zero characteristic.