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A global structure theorem for the mod 2 Dickson algebras, and unstable cyclic modules over the Steenrod and Kudo–Araki–May algebras

Published online by Cambridge University Press:  16 October 2000

DAVID J. PENGELLEY
Affiliation:
New Mexico State University, Las Cruces, NM 88003, U.S.A.; e-mail: [email protected]
FRANKLIN P. PETERSON
Affiliation:
Massachusetts Institute of Technology, Cambridge, MA 02139, U.S.A.; e-mail: [email protected]
FRANK WILLIAMS
Affiliation:
New Mexico State University, Las Cruces, NM 88003, U.S.A.; e-mail: [email protected]

Abstract

The Dickson algebra Wn+1 of invariants in a polynomial algebra over [ ]2 is an unstable algebra over the mod 2 Steenrod algebra [Ascr ], or equivalently, over the Kudo–Araki–May algebra [Kscr ] of ‘lower’ operations. We prove that Wn+1 is a free unstable algebra on a certain cyclic module, modulo just one additional relation. To achieve this, we analyse the interplay of actions over [Ascr ] and [Kscr ] to characterize unstable cyclic modules with trivial action by the subalgebra [Ascr ]n−2 on a fundamental class in degree 2na. This involves a new family of left ideals [Iscr ]a in [Kscr ], which play the role filled by the ideals [Ascr ][Ascr ]n−2 in the Steenrod algebra.

Type
Research Article
Copyright
2000 Cambridge Philosophical Society

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