This is reflected in the fact that the vacuum expectation value of the field squared is nonzero in quantum field theory. Therefore there exist the so called vacuum fluctuations.

这反映在量子场论中场量平方的真空平均值不为零，这就是所谓的真空涨落。

youdao

You'll notice that there's a little bit of a difference in these equations here from the ones from the other day, which is that you have z squared value in there.

你们会注意到这里的方程,和我们那天的方程,有些小的不一样，这里有z平方。

麻省理工公开课 - 化学原理课程节选

You see an object in motion, you find a and you give a a certain numerical value, 10 meters per second squared.

你看到一个物体在运动,你会发现它的 a,然后给 a 赋值,10 米每秒平方

耶鲁公开课 - 基础物理课程节选

We'll introduce in the next course angular nodes, but today we're just going to be talking about radial nodes, psi and a radial node is a value for r at which psi, and therefore, 0 also the probability psi squared is going to be equal to zero.

将会介绍角节点,但我们今天讲的是，径向节点，径向节点就是指，对于某个r的值,当然，也包括psi的平方，等于,当我们说到s轨道时。

麻省理工公开课 - 化学原理课程节选