Unique Einstein Gravity from Feynman’s Lorentz Condition

The Principle of Equivalence is a central concept of Einstein’s theory of gravitation, which makes gener-ally covariant presentation of that theory extremely convenient for working out and communicating its dynamical detail. Weinberg has pointed out, however, that part of the base physics content of the theory, e.g., its overall stress-energy and conserved four-momentum, is inaccessible to formulations which main-tain strict general covariance. Feynman, whose lectures on gravitation initially pursue an order-by-order construction of the theory, as a by-product arrived at a revelatory insight into the dynamical character of the gravitational field that reaches one step beyond Weinberg’s not yet theory-stipulating separation of the Einstein tensor into its physically dissimilar linear and nonlinear parts. While Einstein’s gauge-imposition of a local conservation principle is a common theme in physical theory, permitting it to spill over into outright solution nonuniqueness clearly isn’t acceptable classical physics. Thus stipulation of Feynman’s gravitational Lorentz condition, which pins down the dynamical character of the gravitational field, is fundamental to physically sensible application of Einstein’s gravity theory