arXiv subjects

Paul Raux

Publications and source records attributed to Paul Raux.

7 recordsLinked to original sources

arXiv2026

Lower bounds on entropy production from dynamical correlation functions

Entropy production is a key property in stochastic thermodynamics. For partially observed and coarse-grained systems, its inference is challenging and typically rests on proven lower bounds. We derive two versions of such bounds based on the asymmetry of experimentally accessible two-time correlation functions of coarse-grained state observables. For non-equilibrium steady states, the bound is valid for arbitrary correlation lag. For time-dependent processes, it requires the limit of vanishing lag. These bounds hold true for any system that follows either a Markovian dynamics or a coupled set of overdamped Langevin equations on some underlying, unobservable level of description. We illustrate the bounds for both types of dynamics and discuss their optimization and potential tightness.

cond-mat.stat-mech↗

arXiv2024

Thermodynamic Circuits 2: Nonequilibrium conductance matrix for a thermoelectric converter

In the linear regime, Onsager's response matrix provides the coupling between heat and charge currents crossing a section of thermoelectric materials of infinitesimal thickness. Integrating this response over the finite thickness of a one-dimensional Thermoelectric Converter (TEC) leads to quadratic heat-force characteristics (Joule's law) and linear current-voltage characteristics (Ohm's law). However, these non-linear characteristic equations are not matrix relation anymore. This prevents from determining the currents degree of coupling, albeit its central role for optimizing energy conversion. Based on current conservation laws, i.e., the linear dependence between internal physical currents (crossing a section of material) or between external ones (exchanged with the environment), we distinguish two relevant basis of physical and fundamental currents. For those, we define non-equilibrium conductance matrices providing the current-force relations of a TEC in any convenient basis. In doing so, we introduce a degree of coupling between heat and charge currents, in line with the work of Kedem and Caplan but beyond weakly irreversible thermodynamics. This demonstrates by example that non-equilibrium conductance matrices constitute effective models for driven systems, as Onsager response matrices do in the linear regime. The sequel papers of this series focus on associating systems modeled in such way.

cond-mat.stat-mech↗

arXiv2024

Thermodynamic Circuits: Modeling chemical reaction networks with nonequilibrium conductance matrices

We derive the nonequilibrium conductance matrix for open stationary Chemical Reaction Networks (CRNs) described by a deterministic mass action kinetic equation. As an illustration, we determine the nonequilibrium conductance matrix of a CRN made of two pseudo-linear sub-networks, called chemical modules, in two different ways: First by computing the nonequilibrium conductances of the modules that are then serially connected. Second by computing the nonequilibrium conductance of the CRN directly. The two approaches coincide, as expected from our theory of thermodynamic circuits.

cond-mat.stat-mech↗

arXiv2024

Thermodynamic Circuits: Association of thermoelectric converters in stationary non-equilibrium

Following up on the recently published circuit theory for thermodynamic devices, we consider networks of Thermo-Electric Converters (TECs) in stationary non-equilibrium. Assuming constant thermoelectric properties, the integration over a finite thickness of the linear local response of the thermoelectric material yields the non-linear current-force characteristics. We show how to derive a choice of nonequilibrium conductance matrix summarizing the current-force characteristics for every available sets of currents and forces. This problem has infinitely many solutions if one considers only thermodynamic constraints. Each solution differs, among others, by the coupling between the currents. Then, we determine the current-force characteristics of the serial (respectively parallel) association of two TECs using the laws of resistance (respectively conductance) matrix addition. For TECs in series, we find current-dependent boundary conditions for each sub-device. Since currents derive from composite potentials, we also associate the derivability and continuity of these potentials at the interfaces with conditions on thermoelectric coefficients. For TECs in parallel, we discuss the possibility of loop currents that are forbidden for the serial association.

cond-mat.stat-mech↗

arXiv2024

Methods and Conversations in (Post)Modern Thermodynamics

Lecture notes after the doctoral school (Post)Modern Thermodynamics held at the University of Luxembourg, December 2022, 5-7, covering and advancing continuous-time Markov chains, network theory, stochastic thermodynamics, large deviations, deterministic and stochastic chemical reaction networks, metastability, martingales, quantum thermodynamics, and foundational issues.

cond-mat.stat-mech↗

arXiv2023

Thermodynamic Circuits I: Association of devices in stationary nonequilibrium

For a circuit made of thermodynamic devices in stationary nonequilibrium, we determine the mean currents (of energy, matter, charge, etc) exchanged with external reservoirs driving the circuit out of equilibrium. Starting from the conductance matrix describing the nonlinear current--force characteristics of each device, we obtain the conductance matrix of the composite device. This generalizes the rule of resistance addition (serial association) or conductance addition (parallel association) in stationary out-of-equilibrium thermodynamics and for multiple coupled potentials and currents of different natures. Our work emphasizes the pivotal role of conservation laws when creating circuits of complex devices. Finally, two examples illustrate the determination of the conservation laws for the serial and parallel associations of thermodynamic devices.

cond-mat.stat-mech↗

arXiv2023

N-States Continuous Maxwell Demon

Maxwell's demon is a famous thought experiment and a paradigm of the thermodynamics of information. It is related to Szilard's engine, a two-state information-to-work conversion device in which the demon performs single measurements and extracts work depending on the state measurement outcome. A variant of these models, the Continuous Maxwell Demon (CMD), was recently introduced by Ribezzi-Crivellari and Ritort where work was extracted every time $\tau$ in a two state model. The CMD was able to extract unbounded amounts of work at the cost of an unbounded amount of information storage. In this work, we built a generalization of the CMD to the N-states case. We obtained generalized analytical expressions for the average work extracted and the information content. We show that the second law inequality for information-to-work conversion is fulfilled. We illustrate the results for N-states with uniform transition rates and for the N=3 case.

cond-mat.stat-mech↗