Savchuk, Yuri
(Луганский национальный университет им. Т. Шевченко, 2004)
We describe the C -algebra generated by four
orthogonal projections p1, p2, p3, p4, satisfying the linear relation
p1 + p2 + p3 + p4 = 2I. The simplest realization by 2 × 2-matrixfunctions
over the sphere S2 is given.