James Espinosa alludes to Dirac's hole theory. It is alive and
well and living in disguise in the Feynman formulation of field theory.
Yes, a hole is a vacancy in an electron sea, both in relativistic field
theory and in the theory of the solid state. Feynman explains this, I
think in his <Theory of Fundamental Processes>.
Regards,
Jack
Adam was by constitution and proclivity a scientist; I was the same, and
we loved to call ourselves by that great name...Our first memorable
scientific discovery was the law that water and like fluids run downhill,
not up.
Mark Twain, <Extract from Eve's Autobiography>