On the second law of thermodynamics: An ideal-gas flow spontaneously induced by a locally nonchaotic energy barrier

TL;DR

This paper demonstrates that local nonchaotic particle dynamics can induce a spontaneous, global flow in an isolated system, challenging traditional thermodynamic principles and expanding understanding of entropy and energy behavior.

Contribution

It introduces the concept of local nonchaoticity via a narrow energy barrier, showing how it can generate spontaneous flows and entropy decrease beyond the second law.

Findings

Entropy can decrease in isolated systems.

Spontaneous global flow can be induced by local nonchaotic barriers.

Energy properties of large systems can be nontrivial and non-Boltzmann.

Abstract

People are well aware that, inherently, certain small-scale nonchaotic particle movements are not governed by thermodynamics. Usually, such phenomena are studied by kinetic theory and their energy properties are considered "trivial". In current research, we show that, beyond the boundary of the second law of thermodynamics where Boltzmann's H-theorem does not apply, there are also large-sized systems of nontrivial energy properties: when the system is isolated, entropy can decrease; from a single thermal reservoir, the system can absorb heat and produce useful work without any other effect. The key concept is local nonchaoticity, demonstrated by using a narrow energy barrier. The barrier width is much less than the nominal particle mean free path, so that inside the barrier, the particle-particle collisions are sparse and the particle trajectories tend to be locally nonchaotic. Across the barrier, the steady-state particle flux ratio is intrinsically in a non-Boltzmann form. With a step-ramp structure, the nonequilibrium effect spreads to the entire system, and a global flow is generated spontaneously from the random thermal motion. The deviation from thermodynamic equilibrium is steady and significant, and compatible with the basic principle of maximum entropy. These theoretical and numerical analyses may shed light on the fundamentals of thermodynamics and statistical mechanics.