Abstract
Let H denote a subgroup of the unitary group U(R, Λ) which is normalized by EU(J, ΓJ) for some form ideal (J, ΓJ) of a commutative form ring (R, Λ). We prove that H satisfies a "sandwich" property, i.e., there exists a form ideal (I, ΓI) such that EU(I, ΓI) ⊆ H ⊆ U(I: J7, Ω) for some form ideal (I: J7, Ω). This answers a conjecture of Bak (1967) in the stable case.
Original language | English |
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Pages (from-to) | 607-619 |
Number of pages | 13 |
Journal | Mathematical Proceedings of the Cambridge Philosophical Society |
Volume | 143 |
Issue number | 3 |
DOIs | |
Publication status | Published - Nov 2007 |
Externally published | Yes |