게시판

일정

Problem of the week

Let \(A\) be an \(n\times n\) matrix with complex entries. Prove that if \(A^2=A^*\), then \[\operatorname{rank}(A+A^*)=\operatorname{rank}(A).\] (Here, \(A^*\) is the conjugate transpose of \(A\).) (This is the last problem of this semester. Thank you for participating KAIST Math Problem of the Week.)