给出了超有限因子到其中的套代数的对角上的忠实正常的条件期望的一个刻画,证明了超有限因子中的套代数的中心恰好是纯量构成的.举例说明了超有限因子中套代数的理想结构与Hilbert空间上的套代数的理想结构之间的本质不同.
The description is given for the faithful normal conditional expectation from a hyperfinite factor onto the diagonal of nest algebra of the hyperfinite factor. It is proved that center of the nest algebra is the scalar algebra. It also gives an example, of which the structure of the ideals of the nest algebra is different from that of nest algenra of Hilbert space.