# Experimental study of the energy flux between two NESS thermostats

When |
Oct 26, 2021
from 11:00 to 12:00 |
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Where | Salle des thèses |

Attendees |
Antoine Naert |

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We address the question of energy transport in dissipative systems as a pivotal out-of-equilibrium feature. The experimental setup consists in two coupled granular gas Non-Equilibrium Steady State (NESS) heat baths, in which 2 cm scale rotors are embedded. These 1D Brownian-like mobiles are electro-mechanically coupled by a resistor R, allowing energy to flow between them. This resistor R allows measuring the flux and the temperatures in each bath simultaneously. The mean flux is non-zero if the effective temperatures of the baths differ: we observe that the mean flux is proportional to the temperature gradient. Varying R, we show that, in the limit of non-dissipative coupling (R —> 0), the heat flux obey the ‘eXchange Fluctuation Theorem’ (XFT), in a form proposed by Jarzynski and Wòjcik in 2004, for the fluctuations of the flux between finite-size equilibrium heat baths. We also varied the gas density on one side, which amounts to vary the Kramers time in one of the coupled stochastic equations of motion of the rotors. We investigated the statistics of the flux in such configuration for various densities but zero gradient. A simple model is derived to describe these PDFs. We also obtained preliminary results on the transport coefficients of the associated Fokker-Planck equation for the fluctuations of the energy flux. These results, obtained with granular gas thermostats experiments, are representative of a large class of NESS systems.