On reduction of block matrices in a Hilbert space
We study the problem of the reduction of self-adjoint block matrices $B = (B_ij)$ with given graph by a group of unitary block diagonal matrices. Under the condition that the matrices $B^2$ and $B^4$ are orthoscalar, we describe the graphs of block matrices for which this problem is a problem of *-finite, *-tame, or *-wild representation type.
English version (Springer): Ukrainian Mathematical Journal 61 (2009), no. 10, pp 1578-1588.
Citation Example: Omel’chenko P. V. On reduction of block matrices in a Hilbert space // Ukr. Mat. Zh. - 2009. - 61, № 10. - pp. 1338-1347.