In the genuine thought of its author, synergy should encompass any space energy of interaction. Nevertheless the relationship S = m.c2 doesn't clearly explain why charges are repelling or attracting.
A charge Q, which creates a field around it, should have a similar influence in the surrounding space such as a mass has with gravitation. In that case the synergy S = m.c2 would contain the electrostatic energy so that:
S = m.c2 = S0 + 1/2.ε.E2
Where:
S is the synergy around the charge
S0 is the space synergy without charge
E is the electric field generated from Q
The space influence around the charge having a spherical symmetry, does S only depend on a distance r to the charge. Applying the formula of the electric field generated from Q, expression (1) becomes:
S - S0 = 1 / ( 32.π2 .ε ). ( Q / r2 )2 (2)
|grad S| = -1 / ( 8.π2 .ε ).Q2 /r5 (3)
|grad S| = dS/dr = c2 .dm/dr + 2.m.c.dc/dr (4)
Up to now, has a gravitation field never be observed around an electrical charge, so that no gravitation acceleration is generated by Q and seemingly dc/dr = 0. Thus only the mass density of space would decrease around the charge by following the expression below:
dm/dr = -1 / ( 8.π2 .ε.c2 ).Q2 /r5 (3)
Although Synergetics clearly establishes the relationship between gravitation and a decrease of the space speed of light around mass, the mechanism of electrostatics forces remains a mystery that ends upon two possible tracks of research:
That Synergy encompasses electrostatics energy would imply the space density of mass around a charge to drop down. First, that decrease has yet no physical interpretation (although it could explain why Lorentz's forces don't fit the principle of reaction). Second, it doesn't explain anymore the reason of the electrostatics force.
Synergy doesn't include the electrostatics energy, so that its definition should be restricted to inertial energy. In that case, electrostatics influences space by another kind of influence which has no consequence on the inertial synergy of space.
While STEM-physics can't encompass electrostatics, it can't actually be qualified a unifying theory. Moreover the question remains and also illustrates how Synergetics is a promising but unachieved theory that needs your involvement.