The "living vaccuum" was obvious to everyone by 1930, it didn't require a discoverer. Perhaps you should credit <PERSON>, perhaps <PERSON>, perhaps <PERSON>, perhaps <PERSON>, perhaps <PERSON>, perhaps <PERSON>/<PERSON>, perhaps <PERSON>, who knows.
I would credit <PERSON>, <PERSON>, and <PERSON>, for the development of stationary state perturbation theory. The <PERSON> <PERSON> ideas allowed for virtual atomic transitions, between absorption and emission of light, and <PERSON>'s perturbation theory allowed you to calculate the properties of eigenstates from these virtual states.
Once the quantum field theory was formulated by <PERSON>, <PERSON>, <PERSON> and others, the stationary states were clearly fixed particle occupation number states, and virtual states became virtual particles automatically, without any need for discovery, because the idea of virtual states was already understood.
One major motivation for the quantum field concept came from the <PERSON> paradox--- the <PERSON> equation, if interpreted as a single particle equation, is inconsistent because it allows transmission and reflection coefficients to add up to more than one. This violates the basic ideas of probability. <PERSON> was a major unsung player in the development of early quantum field theory.
Aside from fluctuating virtual particles, there are other concepts of dynamical vacuum which are different, and which are associated with different people:
* The Dirac sea: this picture of positrons as electron-holes in the filled relativistic negative energy band is very physical, and due to Dirac alone.
* Spontaneous symmetry breaking in vacuum by condensates: This idea is probably best attributed to the elder <PERSON>, who believed that these models will explain all of physics from a fundamental Fermi field. The notion of spontaneous symmetry breaking is already present in <PERSON>'s analysis of a spreading S-wave of a charged particle in a bubble chamber, the particle makes a track, even through it's wave description is superficially spherically symmetric. 682
<PERSON>'s particular theory of everything doesn't work, but the idea of spontaneous symmetry breaking was made into a correct theory by <PERSON>, who discovered the quark chiral condensate breaks approximate chiral symmetry, and made a model of this with <PERSON>.
* Higgs mechanism: This is due to <PERSON> and <PERSON>, also <PERSON> and <PERSON>, <PERSON>, <PERSON>. This idea is that the <PERSON> condensate can be charged and therefore superconducting.
* QCD glue condensates: this is probably best attributed to <PERSON>,<PERSON> and <PERSON>. The idea of a glue condensate was floating around at the time, but they gave a way to quantitate the amount of glue.
* Dual superconductor model of confinement: This idea is due to several people, but <PERSON> is most notable. <PERSON>/<PERSON> theory made it respectable by giving quantitative exactly solvable models where you can understand the mechanism qualitatively.
There are also failed dynamical vacuum models
* Lumineferous Ether: The 19th century idea is that there are mechanical stresses in a material filling space which are responsible for electric and magnetic fields.
* Vortex atoms: <PERSON>'s idea that atoms are vortices in ether-flow.
* Teleparallel gravity: Right after developing General Relativity, <PERSON> postulated the notion of teleparallelism, a field which would tell you which direction is which at far away points. This breaks general coordinate invariance, and I don't know this theory, but it wasn't taken seriously by people, including <PERSON>. I think this is just one of the things he had in the back of his head from the many years working on GR, and he wanted to get it out. This theory is a kind of ether, and sometimes people say "<PERSON> embraced the ether later in life", they are talking about teleparallel ether, which (I presume, I didn't read it) is relativistically invariant and has no relation to the lumineferous ether. 800