Entropy and Non-Collapse in Lorentzian Geometry

In this paper, we establish a geometric correspondence between the Lorentzian Raychaudhuri equation and Perelman’s non-collapsing theorem for the Ricci flow. By interpreting the Raychaudhuri equation as a Lorentzian analogue of Ricci flow, we connect geodesic focusing in general relativity to the monotonicity and entropy functionals in geometric analysis. Through this correspondence, we derive a Lorentzian non-collapsing theorem and introduce a covariant entropy functional governing causal volume evolution. Finally, we propose the concept of geodesic entropy capacity—a curvature-bounded limit on the information that can be stored in spacetime regions—which unifies geometric, thermodynamic, and informational aspects of gravity.