I want to find log (A + B ) where A and B are matrices.
The context is that I want to find the Von Neumann entropy which is given by:
$Entropy = - Trace [\rho log (\rho) ]$
where $\rho$ is a matrix.
Now, my problem is computing the V. N. entropy analytically when $\rho = \rho_{0} + \delta\rho$. For this I need to know $log (\rho_{0} + \delta\rho)$
Note that all $\rho$s are matrices.