PS to answer

Murad's or is it Z's question?

In classical

GR the vacuum is assumed to be

non-dispersive in the coupling

8piG/c^4 of applied stress-energy current density's ability to manipulate the local

geometrodynamical field

Ruvwl and its global patterns of geodesic deviation.

If one makes the vacuum's virtual electron-positron pairs disperse light with strong magnetic fields etc in a small region - then it's the same problem as in my

DARPA-NASA Star Ship "Low Power Warp Drive" paper for real meta-materials.

It's clear from Richard

Tolman's 1934 classic "Relativity, Thermodynamics, & Cosmology" that

1) the macroscopic theory of EM fields is not completely derived from the microscopic theory.

2) the way to proceed is to

renormalize all the couplings into zero rank tensor (scalar invariant) form - as I do in my paper - and to keep the local dynamical

Euler-Lagrange field equations of all the matter fields generally covariant as well as locally

Lorentz invariant - which I do.

3) of course we now know as

Tolman did not in 1934 about

P.W. Anderson's More is Different --->

Higgs-Goldstone spontaneous breakdown of continuous dynamical symmetries - modifying

Noether's theorem etc. in which the ground states need not manifest all the symmetries of the

Euler-Lagrange field equations from the Action Principle.

For example, we have an absolute cosmic frame of rest with global time (isotropy of

CMB with a temperature measure of time) not in violation of

GR but as a valid solution of the

GR Euler-Lagrange field equations.