By solving these equations, statistical expressions of expectation and mean square covariance about eigenvalues will be gotten.

求解方程组可得到结构特征值的均值和均方差的统计特征的数值表达式。

youdao

In the quantum statistical theory, the density operator is introduced in the statistical system. The expectation value of an obeservable can be obtained by the use of the density operator.

在量子统计中，对统计系综引入了密度算符，力学量的平均值可以利用密度算符求出。

youdao