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THE DECOMPOSITION OF LIE POWERS

Published online by Cambridge University Press:  09 June 2006

R. M. BRYANT
Affiliation:
School of Mathematics, University of Manchester, P.O. Box 88, Manchester, M60 1QD, United [email protected]
M. SCHOCKER
Affiliation:
Department of Mathematics, University of Wales Swansea, Singleton Park, Swansea, SA2 8PP, United [email protected]
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Abstract

Let $G$ be a group, $F$ a field of prime characteristic $p$ and $V$ a finite-dimensional $FG$-module. Let $L(V)$ denote the free Lie algebra on $V$ regarded as an $FG$-submodule of the free associative algebra (or tensor algebra) $T(V)$. For each positive integer $r$, let $L^r (V)$ and $T^r (V)$ be the $r$th homogeneous components of $L(V)$ and $T(V)$, respectively. Here $L^r (V)$ is called the $r$th Lie power of $V$. Our main result is that there are submodules $B_1$, $B_2$, ... of $L(V)$ such that, for all $r$, $B_r$ is a direct summand of $T^r(V)$ and, whenever $m \geqslant 0$ and $k$ is not divisible by $p$, the module $L^{p^mk} (V)$ is the direct sum of $L^{p^m} (B_k)$, $L^{p^{m - 1}} (B_{pk})$, ..., $L^1 (B_{p^mk})$. Thus every Lie power is a direct sum of Lie powers of $p$-power degree. The approach builds on an analysis of $T^r (V)$ as a bimodule for $G$ and the Solomon descent algebra.

Type
Research Article
Copyright
2006 London Mathematical Society

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