Could electron scatter off vacuum fluctuations?

[asya]

Electron can scatter off virtual photon of Coulomb field (or even emit real photon). But why it cannot do the same off virtual photons of vacuum fluctuations without external field?

 

[mfb]

Energy and momentum are conserved. Such a scattering process would change them.

 

[asya]

Intuitively I understand that.
But formally what is a difference between a virtual photon of Coulomb field and a virtual photon of ground state vacuum fluctuations? Why in the first case conservation lows are OK but in the second one not?

 

[mfb]

The virtual photon from the Coulomb field has a "connection" to something else where it can transfer momentum to.

 

[asya]

Yes, I see...
Thank you!