Simple Gravity II: Strong-Field Structure and Radiative Dynamics (Revised Version)

We present a nonlinear scalar-field formulation of gravity in which the strong-field regime is derived directly from the field equation without introducing spacetime curvature. The theory is defined by a single scalar potential with intrinsic nonlinear self-interaction. An exact field redefinition reduces the vacuum equation to Laplace’s equation, allowing a closed-form spherical solution. This solution naturally produces key strong-field features, including a photon sphere and an innermost stable circular orbit (ISCO), emerging from the internal structure of the field. Using this framework, we derive the orbital dynamics of compact binaries and obtain a finite inspiral cutoff associated with the breakdown of stable circular motion. The radiative sector is described by perturbations of the exponential field variable, leading to a consistent quadrupole radiation model with a single scalar degree of freedom. The theory predicts a slower inspiral relative to general relativity, a larger accumulated phase, and a dynamically determined high-frequency cutoff. The formulation provides a non-geometric interpretation of gravity and offers an alternative perspective on strong-field gravitational phenomena. The internal consistency between the static, dynamical, and radiative sectors is demonstrated explicitly, while the full quantitative normalization of the radiative sector is identified as an area for further refinement. This version supersedes a previous upload of the same work, correcting internal inconsistencies in the radiative sector and ensuring full consistency between power, chirp, and phase evolution.