Date: Feb 26, 2013 10:19 AM Author: Jose Carlos Santos Subject: Unitary equivalence of real matrices Hi all,

Let A an B be two square matrices over the reals with the same size and

suppose that they are unitarily equivalent, that is, that there is an

unitary matrix U such that U.A.U^{-1} = B. Does it follow that there is

an orthogonal real matrix M such that M.A.M^{-1} = B?

Best regards,

Jose Carlos Santos