Simple Gravity II: Dynamical Structure and Radiation

This work presents Simple Gravity II, a scalar-field formulation of gravitation that reproduces key observational features of compact binary inspirals without invoking spacetime curvature. The theory is based on a nonlinear scalar field equation and a modified particle Lagrangian incorporating both temporal and spatial coupling to the gravitational potential. Within this framework, we derive orbital dynamics, energy balance, and gravitational radiation in a self-consistent manner. The formulation admits a well-defined radiative sector, including waveform generation, energy flux, and chirp evolution. The frequency-domain phase is obtained explicitly and follows the characteristic f^{-5/3} scaling observed in gravitational-wave signals. The normalization of the radiative sector is fixed internally through consistency conditions, eliminating free parameters at leading order. The results show that a scalar-field approach can provide an effective description of inspiral phenomenology while maintaining consistency with known observational behavior. This work represents Part II of the Simple Gravity program, focusing on the dynamical and radiative structure of the theory. The strong-field regime remains under investigation and will be addressed in future developments.