The Origin of Particle Stability, Particle Generation in the Early Universe, the Nature of Neutron Decay, and the Structure of Dark Matter ——A Particle Physics Review Based on the First-Principle Unified Theory of Light Strings

Based on the axiom system of the First-Principle Unified Theory of Light Strings, this paper systematically addresses four fundamental problems: the origin of particle stability, the generation and screening of particles in the early universe, the microscopic mechanism of neutron decay, and the physical configuration of dark matter. Using the intrinsic elasticity of light strings, same-frequency resonant phase locking, and standing-wave closure conditions, this paper derives the stable frequency interval of closed light string particles and clarifies that electrons and protons are the only two stable elementary particles in the universe. Neutrons are asymmetric metastable composites formed under high field pressure. Three kinds of proton–electron composite structures (ordinary atoms, neutrons, dark matter) are compared. The symmetric proton–two-electron configuration is proposed as the physical essence of dark matter, which is electromagnetically neutral, purely gravitational, long-term stable, and consistent with astronomical observations. This paper completes the logical chain of particle physics and cosmology under the First-Principle Unified Theory of Light Strings.