Stellar Senescence: The Red Giant Phase as Action Collapse

The transition from main sequence to red giant phase is conventionally modeled as hydrogen exhaustion followed by shell burning and envelope expansion. This study reframes red giant evolution as catastrophic Action collapse—the simultaneous decay of density and spin that terminates the dynamic compression required for core fusion. As stellar radius increases, both structural density (D) and rotational velocity (S) decrease, causing Action (A= M (D·S)) to approach zero. Analysis of a 1.16 M⊙ star demonstrates Action reduction by a factor of∼400, 000 during red giant transition. The framework explains red giant expansion as the physical manifestation of Action stagnation and connects envelope shedding to second generation stellar succession