Let $A, B$ be nilpotent $n\times n$ matrices over the field $K$. Is the following correct?
If $A$ and $B$ has the same degree of nilpotency, then $\operatorname{rank} A = \operatorname{rank} B $
Let $A, B$ be nilpotent $n\times n$ matrices over the field $K$. Is the following correct?
If $A$ and $B$ has the same degree of nilpotency, then $\operatorname{rank} A = \operatorname{rank} B $
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This is not correct. As a counter-example, consider $$ A = \pmatrix{0&1\\&0\\&&0\\&&&0}, \quad B = \pmatrix{0&1\\&0\\&&0&1\\&&&0} $$ which both have nilpotency degree $2$.
This is true, however, for $n \leq 3$, since nilpotent matrix of the same nilpotency degree are necessarily similar (since they have the same Jordan form).