09:15  09:30

JanMichael Rost MPIPKS & Scientific Coordinators
Workshop Opening

09:30  10:00

Felix Ritort
(Universitat de Barcelona)
Experimental measurement of informationcontent in nonequilibrium systems
Biology is intrinsically noisy at all levels, from molecules to cells, tissues, organs, communities and ecosystems. While thermodynamic processes in ordinary matter are driven by freeenergy minimization, living matter and biology delineate a fascinating nonequilibrium state predominantly governed by information flows through all organizational levels. Whereas we know how to measure energy and entropy in physical systems we have poor knowledge about measuring informationcontent in general. Recent developments in the fields of stochastic thermodynamics and thermodynamicinformation feedback combined with single molecule experiments show the way to define informationcontent in nonequilibrium systems. In this talk I will describe how to measure informationcontent in two classes of nonequilibrium systems. First, I will introduce the Continuous Maxwell Demon, a new paradigm of informationtoenergy conversion, and demonstrate how work extraction beats the Landauer limit without violating the second law. Next, I will demonstrate the validity of a fluctuation theorem in nonequilibrium systems under continuoustime feedback and show how to measure informationcontent in such conditions. Second, I will introduce a mutational ensemble of DNA hairpin folders and show how to measure informationcontent in this context. A definition of informationcontent applicable to generic disordered populations is proposed. All results are tested in single molecule pulling experiments.

10:00  10:30

Raphael Chetrite
(CNRS)
On GibbsShannon Entropy
This talk will be focus on the question of the physical contents of the GibbsShannon entropy outside equilibrium.
Article : GavrilovChetriteBechhoeffer : Direct measurement of weakly nonequilibrium system entropy is consistent with GibbsShannon form. PNAS 2017.

10:30  11:00

coffee break

11:00  11:30

Ludovic Bellon
(University of Lyon)
The quest for the missing noise in a micromechanical system out of equilibrium
Equipartition principle plays a central role in the understanding of the physics of systems in equilibrium: the mean potential and kinetic energy of each degree of freedom equilibrates to $k_BT/2$, with $k_B$ the Boltzmann constant and $T$ the temperature. This equality is linked to the fluctuationdissipation theorem (FDT): fluctuations of one observable are proportional to the temperature and dissipation in the response function associated to that observable. In non equilibrium situations however, such relations between fluctuations and response are not granted, and excess noise is usually expected to be observed with respect to an equilibrium state [1].
In this presentation, we show that the opposite phenomenon can also be experimentally observed: a system that fluctuates less than what would be expected from equilibrium ! Indeed, when we measure the thermal noise of the deflexion of a microcantilever subject to a strong stationary temperature gradient (and thus heat flow), fluctuations are much smaller that those expected from the system mean temperature.
We will first present the experimental system, an atomic force microscope (AFM) microcantilever in vacuum heated at its free extremity with a laser. We will show that this system is small enough to have discrete degrees of freedom but large enough to be in a nonequilibrium steady state (NESS). We will then estimate its temperature profile with the mechanical response of the system [2], and observe that equipartition theorem can not be applied for this NESS: the thermal noise of the system is roughly unchanged while its temperature rises by several hundred degrees ! We will explain how a generalized FDT taking into account the temperature field can account for these observations, if dissipation is not uniform. Further experimental evidences of the validity of this framework will conclude the presentation [3].
We acknowledge the support of ERC project OutEFLUCOP and ANR project HiResAFM.
[1] L. Conti, P. D. Gregorio, G. Karapetyan, C. Lazzaro, M. Pegoraro, M. Bonaldi, and L. Rondoni, Effects of breaking vibrational energy equipartition on measurements of temperature in macroscopic oscillators subject to heat flux, J. Stat. Mech. P12003 (2013)
[2] F. Aguilar, M. Geitner, E. Bertin and L. Bellon, Resonance frequency shift of strongly heated microcantilevers, Journal of Applied Physics 117, 234503 (2015)
[3] M. Geitner, F. Aguilar, E. Bertin and L. Bellon, Low thermal fluctuations in a system heated out of equilibrium, Physical Review E 95, 032138 (2017)

11:30  12:00

Livia Conti
(Istituto Nazionale di Fisica Nucleare)
Nonequilibrium fluctuations in gravitational wave interferometers
Gravitational wave interferometers have recently made the first detections, opening the era of gravitationalwave and multimessenger astronomy. In the coming years both LIGO and Virgo will undergo a planned series of experimental upgrades to further increase the sensitivity; moreover a completely new generation of instruments is being studied with the aim of increasing the astrophysical reach by at least a factor 10, while also extending the bandwidth towards lower frequencies. In both cases, the design choices depend critically on the full control of the noise budget: this is a rather complex task due to the level of sophistication of these macroscopic instruments which are designed to be limited by a combination of few fundamental noise sources. Together with quantum noise and local gravity gradients, thermal noise is expected to be a dominating contribution to the instrument ultimate noise. Its contribution is traditionally estimated under the hypothesis of thermal equilibrium, in spite of the thermal gradients and heat fluxes that are present in the instruments' key components. While the deviation may be modest in current detectors, futures designs relying on cryogenic operation foresee much more extreme nonequilibrium conditions that can severely compromise the applicability of predictions made assuming equilibrium. The reason for the widespread and often improper assumption of equilibrium is that, for solids, a viable theory that describes thermal noise away from thermodynamic equilibrium does not exist yet. Experimental data is scarce, but does suggest the possibility, in some cases, of a substantial enhancement of spontaneous fluctuations compared to the equilibrium condition, similarly to what is observed in fluids. I will discuss the design of gravitational wave interferometers focusing on nonequilibrium driving cases and will present experimental data on the spontaneous fluctuations of solids in nonequilibrium steady states.

12:00  12:20

Suriyanarayanan Vaikuntanathan
(University of Chicago)
Dissipation induced transitions in elastic membranes and materials
Stochastic thermodynamics provides a useful set of tools to analyze and constrain the behavior of far from equilibrium systems. In this talk, we will report an application of ideas from stochastic thermodynamics to the problem of membrane growth. Nonequilibrium forcing of the membrane can cause it to buckle and undergo a morphological transformation. We show how ideas from stochastic thermodynamics, in particular, a recent application to selfassembly, can be used to phenomenologically describe and constrain morphological changes excited during a nonequilibrium growth process.

12:20  13:20

lunch

13:20  14:00

discussion

14:00  14:30

Udo Seifert
(University of Stuttgart)
From stochastic thermodynamics to thermodynamic inference
Stochastic thermodynamics provides a framework to describe small driven systems using thermodynamic notions. Since the conceptual basis is now firmly established, the challenge is to explore whether and how these concepts can be used to infer otherwise hidden properties of systems. After recalling the foundations, I will report on our recent progress following this strategy. In particular, I will elucidate the form of entropy production in active systems and derive modelindependent bounds on the efficiency of molecular motors and small heat engines. For the latter, I will resolve the recent debate whether or not Carnot efficiency can be reached at finite power.

14:30  14:50

Matteo Polettini
(University of Luxembourg)
Effective fluctuation and response theory
The response of thermodynamic systems perturbed out of an equilibrium steadystate is described by the reciprocal and the fluctuationdissipation relations. The socalled fluctuation theorems extended the study of fluctuations far beyond equilibrium. All these results rely on the crucial assumption that the observer has complete information about the system. Such a precise control is difficult to attain, hence the following questions are compelling: Will an observer who has marginal information be able to perform an effective thermodynamic analysis? Given that such observer will only establish local equilibrium amidst the whirling of hidden degrees of freedom, by perturbing the stalling currents will he/she observe equilibriumlike fluctuations? We model the dynamics of open systems as Markov jump processes on finite networks. We establish that: 1) While marginal currents do not obey a fullfledged fluctuation relation, there exist effective affinities for which an integral fluctuation relation holds; 2) Under reasonable assumptions on the parametrization of the rates, effective and "real" affinities only differ by a constant; 3) At stalling, i.e. where the marginal currents vanish, a symmetrized fluctuationdissipation relation holds while reciprocity does not; 4) There exists a notion of marginal timereversal that plays a role akin to that played by timereversal for complete systems, which restores the fluctuation relation and reciprocity. The above results hold for configurationspace currents, and for phenomenological currents provided that certain symmetries of the effective affinities are respected  a condition whose range of validity we deem the most interesting question left open to future inquiry. Our results are constructive and operational: we provide an explicit expression for the effective affinities and propose a procedure to measure them in laboratory.

14:50  15:10

Stefano Bo
(Nordic Institute for Theoretical Physics)
Driven anisotropic diffusion at boundaries: noise rectification and particle sorting
We study the diffusive dynamics of a Brownian particle in the proximity of a flat surface under nonequilibrium conditions, which are created by an anisotropic thermal environment with different temperatures being active along distinct spatial directions. By presenting the exact timedependent solution of the FokkerPlanck equation for this problem, we demonstrate that the interplay between anisotropic diffusion and hardcore interaction with the plain wall rectifies the thermal fluctuations and induces directed particle transport parallel to the surface, without any deterministic forces being applied in that direction. Based on current micromanipulation technologies, we suggest a concrete experimental setup to observe this novel noiseinduced transport mechanism. We furthermore show that it is sensitive to particle characteristics, such that this setup can be used for sorting particles of different sizes.

15:10  16:00

discussion

16:00  16:30

coffee break

16:30  17:30

stet18 colloquium
Jukka Pekola (Aalto University)
Thermodynamics of superconducting quantum circuits

17:30  18:30

discussion

18:30  19:30

dinner

19:30

poster session I (focus on even poster numbers)
