Pd. Mannheim et D. Kazanas, NEWTONIAN LIMIT OF CONFORMAL GRAVITY AND THE LACK OF NECESSITY OF THE2ND-ORDER POISSON EQUATION, General relativity and gravitation, 26(4), 1994, pp. 337-361
We study the interior structure of a locally conformal invariant fourt
h order theory of gravity in the presence of a static, spherically sym
metric gravitational source. We find, quite remarkably, that the assoc
iated dynamics is determined exactly and without any approximation at
all by a simple fourth order Poisson equation which thus describes bot
h the strong and weak field limits of the theory in this static case.
We present the solutions to this fourth order equation and find that w
e are able to recover all of the standard Newton-Euler gravitational p
henomenology in the weak gravity limit, to thus establish the observat
ional viability of the weak field limit of the fourth order theory. Ad
ditionally, we make a critical analysis of the second order Poisson eq
uation, and find that the currently available experimental evidence fo
r its validity is not as clearcut and definitive as is commonly believ
ed, with there not apparently being any conclusive observational suppo
rt for it at all either on the very largest distance scales far outsid
e of fundamental sources, or on the very smallest ones within their in
teriors. Our study enables us to deduce that even though the familiar
second order Poisson gravitational equation may be sufficient to yield
Newton's Law of Gravity it is not in fact necessary.