  It was proposed by Haisch, Rueda and Puthoff (Phys. Rev. A, 49, 678, 1994)
that the inertia of matter could be interpreted at least in part as a reaction
force originating in interactions between the electromagnetic zero-point field
(ZPF) and the elementary charged consitutents (quarks and electrons) of matter.
Within the limited context of that analysis, it appeared that Newton's equation
of motion, f=ma, could be inferred from Maxwell's equations as applied to the
ZPF, i.e. the stochastic electrodynamics (SED) version of the quantum vacuum.
We report on a new approach which avoids the ad hoc particle-field interaction
model (Planck oscillator) of that analysis, as well as its concomitant
formulational complexity. Instead, it is shown that a non-zero ZPF momentum
flux arises naturally in accelerating coordinate frames from the standard
relativistic transformations of electromagnetic fields. Scattering of this ZPF
momentum flux by an object will yield a reaction force that may be interpreted
as a contribution to the object's inertia. This new formulation is properly
covariant yielding the relativistic equation of motion. Our approach is related
by the principle of equivalence to Sakharov's conjecture of a connection
between Einstein action and the vacuum. If correct, this concept would
substitute for Mach's principle and imply that no further mass-giving
Higgs-type fields may be required to explain the inertia of material objects,
although extensions to include the zero-point fields of the other fundamental
interactions may be necessary for a complete theory of inertia.
