Edwin,
I did not mean to give the impression that i agree with the assumptions of quantum field theory. Let me explain the point I am interested in regarding "local interaction".
Assume, for the moment, that Newton's law of gravity is valid, namely that gravity is dependent on the inverse square of the distance between masses. If this force were to act instantaneously at a distance, then all masses, even those infinitely far away, would have to be integrated into the total force. But, if the effect of the force has to travel, at a finite speed, then a distance threshold exists, at which masses more distant than the threshold have no effect, since the force has not had enough time to propagate out to that distance. Hence, the force law remains an inverse square, out the the threshold distance, then becomes a step-function, and the force becomes identically zero. Furthermore, the distance threshold constantly increases, so that the amount of mass within the threshold also increases.
Comparing such a force, to Newton's force, would result in an apparent repulsive force (dark energy), that is actually not repulsive, but just diminished effective mass, acting upon very distant objects. The force law appears to evolve, but the cause is not a change in the force per unit mass, but a change in the amount of mass that acts upon another mass.
In your master equation, it is not the del operator acting upon the field, but the other side of the equation that I wonder about. I am not sure how the field times the field could represent the situation described above, in which the "effective" field, is a constantly changing subset of the total field. Unlike Newton's case, one cannot integrate over all space in order to determine the field. Determination of the field would be highly dependent on the initial conditions, namely, the distribution of masses, as they are "swept into" the effective threshold range.
It is also interesting to think about General Relativity, from this non-geometric point-of view. Objects do not respond gravitationally to where other objects are, but instead respond to where they used to be. The greatest differences between these two types of response, occur in situations in which the relative geometry changes the fastest. Hence, in the solar system, one would expect the fastest moving planet, Mercury, to have the greatest discrepancy between the two models; like the advance of the perihelion of Mercury.
Rob McEachern