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Apr 19, 2023 at 0:22 comment added Benjamin Steinberg Sorry, in my last comment I meant of order n which is a power of 2
Apr 18, 2023 at 20:12 comment added Benjamin Steinberg If n is a power of 2 the answer to 3 is k=n. Take I+P where P is the permutation matrix of order 2^n corresponding to the cyclic permutation (1,2,...,n)
Apr 18, 2023 at 19:33 history edited Turbo CC BY-SA 4.0
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Apr 18, 2023 at 19:25 comment added Benjamin Steinberg The answer to 4 is no. If n is odd let M be the all ones matrix.
Apr 18, 2023 at 19:13 comment added Benjamin Steinberg The nilpotent elements do not form a subsemigroup. Take E_12 E_21=E_11
Apr 18, 2023 at 16:10 comment added Turbo I think it is called index when the matrix vanishes valnishes. There is no nomenclature for the $k$ introduced.
Apr 18, 2023 at 15:18 history edited Turbo CC BY-SA 4.0
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Apr 18, 2023 at 7:34 comment added Gerry Myerson $M=\pmatrix{1&1\cr0&0\cr}$ has determinant zero, but there are no permutations $P,Q$ such that $PMQ$ is nilpotent.
Apr 18, 2023 at 4:16 history edited Turbo CC BY-SA 4.0
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Apr 18, 2023 at 3:54 history asked Turbo CC BY-SA 4.0