The Lorenz gauge and the Coulomb gauge are in
some sense the extremes in behavior of
the scalar potential. In the one the effects of
a source point propagate with the speed c; in the
other the propagation is at infinite speed. But
there is no reason for a restriction to such limiting
cases. We define the velocity gauge ( v-gauge
for short and actually a class of gauges) to be one in
which the speed of propagation for the scalar
potential is v, an arbitrary speed relative to c. The
velocity gauge has been discussed in classical
electrodynamics by Yang, Brown and
Crothers, and Drury, and in quantum
electrodynamics by Baxter,18 with the names " -
Lorentz gauge," and "velocity gauge."
Brown and Crothers are most explicit; Drury
discusses the equations but does not solve them.
http://arxiv.org/abs/physics/0204034

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