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Two point stabilisers of partition actions of linear groups. (English) Zbl 1156.20314

Summary: A partition of a \(kl\)-dimensional vector space \(V\) is a set of \(l\) subspaces each of dimension \(k\) such that their direct sum is the original space \(V\). We show that, unless \(l=2\), the action of a group \(\overline L\) such that \(\text{PSL}(V)\trianglelefteq\overline L\leq\text{PGL}(V)\) on the set of partitions of \(V\) into \(l\) subspaces of dimension \(k\) is base two: there exist two partitions \(\mathcal V\) and \(\mathcal W\) such that \(\overline L_{\mathcal V,\mathcal W}=1\).
We also show that, given any finite group \(G\), there exist \(k,l\) and partitions \(\mathcal{V,W}\) such that \(\overline L_{\mathcal V,\mathcal W}\cong G\).
These results complement work the author has done with partition actions of the symmetric groups.

MSC:

20G40 Linear algebraic groups over finite fields
20B30 Symmetric groups
Full Text: DOI

References:

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