Hi, I have a matrix : $W=I+U^TV$ - $dim(W)=(D,D)$ - $dim(U)=dim(V)=(N,D)$ with $N < < D$ I need it to be orthogonal ie $W^TW=I$ which gives me : $V^TU+U^T+V^TUU^TV=0$ From that point, i don't know where to go. Have anyone got some ideas about that issue ? Cheers Guillaume