Given a real nxn matrix A and a perturbation of the form A+R where R is chosen uniformly at random in [-r,r]nxn i.e. each entry of R is in the segment [-r,r] for some given r>0, what is the probability that A+R would be real diagonalizable ? i.e. what is the probability for the existance of real invertible matrix T such that T^{-1}(A+B)T would have the form of block diagonal with real blocks of sizes 1x1 or 2x2 only ?
Another related (but not equivalent) question: what is the probablility that all the eigenvalues of A+R would be different (and therefore, A+R would be real diagonalizable) ?