Dirac's negative energy sea

[planetology]

In every situation I'm aware of, energy states exist because of some
force that gives rise to them (dE/dx, y'know). What force did Dirac
envision as giving rise to his proposed negative energy states (from
which antimatter arises)? When I see it described in textbooks, the
states are shown as being in increments of mc^2. If it were
electromagnetic or some such, it seems to me this numerical result would
not necessarily hold.

I suppose I could try reading his paper. Is it available in any of the
online archives?

[David Baker]

> In every situation I'm aware of, energy states exist because of some
> force that gives rise to them (dE/dx, y'know). What force did Dirac
> envision as giving rise to his proposed negative energy states (from
> which antimatter arises)? When I see it described in textbooks, the
> states are shown as being in increments of mc^2. If it were
> electromagnetic or some such, it seems to me this numerical result would
> not necessarily hold.

The energy that is negative in the case of the Dirac "negative energy
sea" is just the kinetic energy. The Dirac equation describes free
particles, so by assumption there is no force acting on them.

Of course, the "negative energy sea" is sort of an outdated way of
looking at the Dirac equation. A more elegant approach treats the
"negative-energy" (really, negative-frequency) states as
positive-energy states of antiparticles. This is implemented by
re-defining what it is to multiply the Dirac wavefunction by a complex
number: when "multiplying by i," you multiply the positive-frequency
part by +i and the negative-frequency part by -i. This gives positive
energy for all solutions.

[sjtjohnson2004@yahoo.com]

re:diracs negative energy . i believe he meant it as a logical
consequence arising from the square root in einstein's energy equation
for a particle with a velocity approaching c . as told by himself in
book "Directions in Physics"P.A.M.Dirac. edited by H hora snd j.r.
shepanski 1978 John Wiley and Sons