Entropies for severely contracted configuration space

TL;DR

This paper explores how dual Tsallis entropy expressions naturally describe systems with severely contracted configuration spaces, linking entropic indices to phase-space contraction and extensivity restoration in nonlinear maps.

Contribution

It introduces a dual entropy framework for systems with contracted configuration spaces, connecting entropic indices to phase-space contraction and extensivity in nonlinear dynamical systems.

Findings

Dual entropy expressions apply to systems with contracted configuration space.

The entropic index $eta>1$ characterizes contraction, while $eta' = 2 - eta$ restores extensivity.

Application to nonlinear maps at chaos transitions demonstrates phase-space contraction effects.

Abstract

We demonstrate that dual entropy expressions of the Tsallis type apply naturally to statistical-mechanical systems that experience an exceptional contraction of their configuration space. The entropic index $\alpha>1$ describes the contraction process, while the dual index $\alpha ^{\prime }=2-\alpha<1$ defines the contraction dimension at which extensivity is restored. We study this circumstance along the three routes to chaos in low-dimensional nonlinear maps where the attractors at the transitions, between regular and chaotic behavior, drive phase-space contraction for ensembles of trajectories. We illustrate this circumstance for properties of systems that find descriptions in terms of nonlinear maps. These are size-rank functions, urbanization and similar processes, and settings where frequency locking takes place.