The semisimple similarity number conjecture for matrix sequences

For n,mNn,m\in\mathbb{N}, let Sn,m\mathcal{S}_{n,m} be the subset of semisimple sequences in the space Vn,mV_{n,m} of m×mm\times m matrix sequences. Define the semisimple similarity number S(m)S(m) by

S(m)=min{kN: nN, A,BSn,m, ABAJBJ J with Jk}.S(m)=\min\{k\in\mathbb{N}:\ \forall n\in\mathbb{N},\ \forall\mathcal{A},\mathcal{B}\in\mathcal{S}_{n,m},\ \mathcal{A}\sim\mathcal{B}\Leftrightarrow\mathcal{A}_{J}\sim\mathcal{B}_{J}\ \forall J\text{ with }|J|\leq k\}.

Semisimple similarity number conjecture. For arbitrary m×mm\times m sequences, not necessarily semisimple, AB\mathcal{A}\sim\mathcal{B} if and only if AJBJ\mathcal{A}_{J}\sim\mathcal{B}_{J} for every index vector JJ with length at most S(m)S(m).

The conjecture proposes that the number of terms needed to test simultaneous similarity for arbitrary matrix sequences is already controlled by the corresponding number for semisimple sequences. The source presents this as a proposed problem and gives no resolution.

Sources & referencesView supporting material

Primary source

Carlos A. A. Florentino, “Simultaneous similarity and triangularization of sets of 2 by 2 matrices”, arXiv:0809.3032 (2008).

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