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Feb 6, 2015 at 0:15 answer added Joe Silverman timeline score: 6
Feb 6, 2015 at 0:01 answer added Douglas Lind timeline score: 5
Feb 5, 2015 at 21:58 vote accept Liam Baker
Feb 5, 2015 at 21:10 comment added Geoff Robinson You need to use that fact that all eigenvalues of $DD^{T}$ are totally positive algebraic integers, and if one or more of them is not 1, its algebraic conjugates have mean value at least $1.5$.
Feb 5, 2015 at 20:45 comment added Geoff Robinson It seems to be Theorem III of "The trace of totally positive and real algebraic integers" by C.L. Siegel, Annals of Maths, 46, 2, (1945), 302-312
Feb 5, 2015 at 20:38 comment added Liam Baker @Goeff can you give a reference for that theorem?
Feb 5, 2015 at 20:11 answer added Qiaochu Yuan timeline score: 7
Feb 5, 2015 at 19:53 comment added Geoff Robinson I am not sure of the general case, but I think that if $D \in {\rm GL}(n,\mathbb{Z})$ is not a "signed permutation matrix", ie $DD^{T} \neq I$, a Theorem of Siegel implies that $\rho(DD^{T}) \geq 1.5$.
Feb 5, 2015 at 19:40 history asked Liam Baker CC BY-SA 3.0