Krystyna Zietak, "On approximation problems with zero-trace matrices"


We consider some approximation problems in the linear space 
of complex matrices with respect to unitarily  invariant norms.
We deal with special cases of approximation of a matrix by zero-trace
matrices. Some characterization of zero-trace matrices are given 
by means of matrix approximation problems.

key words:  matrix approximation, unitarily invariant norms,
zero-trace matrices