Related Experiment Video
Updated: Jan 8, 2026

Methods for Measuring the Orientation and Rotation Rate of 3D-printed Particles in Turbulence
Published on: June 24, 2016
Local entropy production rate of run-and-tumble particles
Matteo Paoluzzi1, Andrea Puglisi2,3, Luca Angelani2
1Sapienza Università di Roma, Dipartimento di Fisica, Piazzale A. Moro 2, I-00185 Rome, Italy.
None:
We study the local entropy production rate and the local entropy flow in active systems composed of noninteracting run-and-tumble particles in a thermal bath. After providing generic time-dependent expressions, we focus on the stationary regime. Remarkably, in this regime the two entropies are equal and depend only on the distribution function and its spatial derivatives. We discuss in detail two case studies relevant to real situations. First, we analyze the case of space-dependent speed describing photokinetic bacteria, cosidering two different shapes of the speed, namely piecewise constant and sinusoidal. Finally, we investigate the case of external force fields, focusing on harmonic and linear potentials, which allow analytical treatment. In all investigated cases, we compare exact and approximated analytical results with numerical simulations.
More Related Videos
11:03An Analog Macroscopic Technique for Studying Molecular Hydrodynamic Processes in Dense Gases and Liquids
Published on: December 4, 2017
11:51Visually Based Characterization of the Incipient Particle Motion in Regular Substrates: From Laminar to Turbulent Conditions
Published on: February 22, 2018
Related Concept Videos
Entropy
Entropy
When an ideal gas expands isothermally, the disorder in the gas increases. From the molecular perspective, the gas molecules have more volume to move around in.
Consider an infinitesimal step in the expansion, which...
Entropy and the Second Law of Thermodynamics
The relation between entropy and disorder can be illustrated with the example of the phase change of ice to water. In ice, the molecules are located at specific sites giving a solid state, whereas, in a liquid form, these molecules are much freer to move. The molecular arrangement has therefore become more randomized. Although the change in average...
The Second Law of Thermodynamics
Third Law of Thermodynamics
Entropy Change in Reversible Processes
The statement can be further generalized to prove that entropy is a state function. Take a cyclic process between any two points on a p-V diagram.