# Quantum fluctuations within an electromagnetic field

1. Jan 20, 2016

### J-eastwood

hello,

I was wondering what caused quantum fluctuations within an electromagnetic field as i recently accepted that there are no virtual particles what causes the energy to fluctuate. here the quantum fluctuations are said to be caused by virtual particles.

essentially i'm asking for an explanation of quantum fluctuations in regards to lattice QFT.

thank you, jonah

2. Jan 20, 2016

### Staff: Mentor

I know of no effects that depends on fluctuations of the quantum vacuum so my answer is they are not needed so forget about them. That they are not needed explains why they don't have to appear in lattice theory.

The Casmir force and spontaneous emission don't require it.

Thanks
Bill

3. Jan 20, 2016

### A. Neumaier

Quantum fluctuations are not caused at all. They are a popular buzzword for the statistical triviality that the variance of a random variable $A$ with zero mean is typically not zero - except that $A$ is now an operator such as (a smeared variant of) $\phi(x)$. Some people therefore think that this deserves a much more mysterious name. (See also this post and its context.)

More precisely, there are two uses of the term; a technical one that means precisely what I wrote, and popular one that associates with the quantum fluctuation weird stuff with a temporal behavior that is not observable, and thus figures only in the minds of those who enjoy quantum mysticism. (For example, the vacuum is temporally completely inert, but the vacuum fluctuations of most fields are nonzero.)

This is explained in more depth in the section ''Does the vacuum fluctuate?'' in Chapter A8: Virtual particles and vacuum fluctuations of my theoretical physics FAQ and other articles of this chapter.

Last edited: Jan 20, 2016