Explicitly, the relation between kinetic energy T and Hermitian Cartesian momentum Pi ( i=1,2,3)is speciously which holds either for the system being free of constraint or for the system in classical limit.

• 动能算符T和三个笛卡儿动量Pi (i =1,2,3)的关系似乎为: 其中Pi (i =1,2,3)为厄密算符。 事实上,这一关系的成立是有条件的:要么不存在约束,要么发生在经典极限下。