(later identified as the negative of entropy), for an ideal gas. : Boltzmann defined is the distribution of molecular velocities.
corresponds to a monotonic increase in entropy as the system reaches its most probable state: the . Controversies and Paradoxes Ludwig Boltzmann, 1844—1906, Whose H theorem - ...
The H-theorem was groundbreaking because it claimed to derive irreversible macroscopic behavior from reversible microscopic laws of motion. This led to two famous challenges: (later identified as the negative of entropy), for