1 | Dirac’s original expression actually involved
the rate of change of the acceleration vector on the right-hand
side. The resulting equation gives rise to the well-known problem
of runaway solutions. To avoid such unphysical behaviour I have
submitted Dirac’s equation to a reduction-of-order procedure
whereby ![]() ![]() ![]() ![]() |
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2 | His analysis was restricted to a
minimally-coupled scalar field, so that ![]() |
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3 | Note that I use ![]() |