Non-equilibrium processes play important and often vital roles at many length- and time-scales, ranging from those characteristic of the organisation of the cell nucleus to those relevant for the flocking of birds. Non-equilibrium statistical mechanics encompasses fundamental tools that are actively being developed and refined to understand such complex phenomena. A crucial factor that has hindered, so far, the formulation of a unified approach to nonequilibrium is the variety of different ways in which various systems can be out of equilibrium. Biological living complexes, glasses or active matter, represent such different systems and pose different challenges that are generally approached from different perspectives.
A key step to improve our understanding of universal non-equilibrium mechanisms at play across scales is to discuss and compare different ideas coming from all different research fields. The meeting will focus on finding a common denominator for theoretical, computational and experimental approaches, so to maximally promote collaborations and knowledge exchange among early career researchers.
We envisage 4 sessions focussing on the following topics: 1) biophysics & polymers, 2) active matter, 3) non-equilibrium statistical mechanics, 4) glasses & disordered systems.
These selected topics are at the forefront of the application of statistical mechanics of non-equilibrium phenomena and represent areas where a significant conceptual progress has been achieved.
Session 1 will cover problems in biophysics and polymers. Polymers are ubiquitous at the cellular level, from the cytoskeleton to the DNA. Contrarily to polymer scientists, tough, biophysicists need to work in the complex environment of the cell, involving elements such as molecular machines that drive the system out of equilibrium. It is important thus for them to be able to combine and utilize the concepts coming from polymer science, active matter and non-equilibrium statistical physics [1]. One important open problem that will be addressed in the workshop is how the genome is organised inside the nucleus of the cells [2-4].
Session 2 will cover active matter, a research area that has attracted high interest in the last decade. Active matter is typically defined as consisting of particles able to pump energy from their environment and convert it into autonomous motion, making the system out-of-equilibrium. Thus, all living systems constitute examples of active matter due to a continual rate of energy consumption at microscopic level (e.g. ATP-to-ADP chemical reactions). One important question we aim to discuss is the effect of the surrounding environment on the non-equilibrium collective behaviour displayed by active systems [5,6], from swimmers in viscoelastic media [7] to topologically protected modes in active fluids [8].
Session 3 will provide theoretical tools and methods from the field of non-equilibrium statistical mechanics to deal with complex non-equilibrium phenomena. Transport and molecular machines will be at the heart of this session, with theoretical discussions on efficiency bounds, simulations of confined systems as well as the application of stochastic thermodynamics to the design of efficient machines, relevant for simple colloidal systems and active molecular processes [9-11].
Session 4 will cover the physics of glasses and dynamical slowing down. This includes systems with complex patterns of relaxation and emerging properties: liquids at very low temperature or dense assemblies of colloidal particles under external stresses, as well as systems in crowded environments such as confined protein systems [12-15]. Their response to non-equilibrium conditions (e.g. during ageing or external/internal driving) is one of the core questions in this area of research, connecting to a variety of competing theoretical scenarios and other fields such as rheology, biophysics and computer science [16].
These topics have been chosen so as to cover a broad spectrum of different research directions in which non-equilibrium physics plays a major role and that display some degree of overlap. This is to ensure: (i) smooth transitions between the sessions, thus conveying the idea that all these topics are interconnected, (ii) stimulating cross-talks among invited speakers from all sessions and (iii) opportunities for the participants to discuss ideas and take them further in the form of new collaborations (independent of their respective PIs) or joint applications for research grants.
References:
[1] Le, Y., Ravasio, R., Brito, C. & Wyart, M., (2017). Architecture and coevolution of allosteric matter. Proceedings of the National Academy of Sciences, Mar, 114 (10)
[2] Brackley, C. A., Johnson, J., Michieletto, D., Morozov, A. N., Nicodemi, M., Cook, P. R., & Marenduzzo, D. (2018). Extrusion without a motor: a new take on the loop extrusion model of genome organization. Nucleus, 9(1), 95-103.
[3] Gibcus, J. H., Samejima, K., Goloborodko, A.,Samejima, I., Naumova, N., Nuebler, J., Kanemaki, M. T., Xie, L., Paulson, J. R., Earnshaw, W. C., Mirny, L. A., Dekker, J., (2018), A pathway for mitotic chromosome formation, Science, 359, 6376.
[4] Tan, L., Xing, D., Chang, C. H., Li, H., & Xie, X. S. (2018). Three-dimensional genome structures of single diploid human cells. Science, 361(6405), 924-928.
[5] Zampetaki, A., Schmelcher, P., Löwen, H., & Liebchen, B. (2019). Taming polar active matter with moving substrates: directed transport and counterpropagating macrobands. New Journal of Physics, 21(1), 013023.
[6] Ramananarivo, S., Mitchel, T., & Ristroph, L. (2019). Improving the propulsion speed of a heaving wing through artificial evolution of shape. Proceedings of the Royal Society A, 475(2221), 20180375.
[7] Zöttl, A., & Yeomans, J. M. (2019). Enhanced bacterial swimming speeds in macromolecular polymer solutions. Nature Physics, 1.
[8] Banerjee, D., Souslov, A., Abanov, A. G., & Vitelli, V. (2017). Odd viscosity in chiral active fluids. Nature communications, 8(1), 1573.
[9] Pietzonka, P., & Seifert, U. (2018). Universal trade-off between power, efficiency, and constancy in steady-state heat engines. Physical Review Letters, 120(19), 190602.
[10] Puertas, A. M., Malgaretti, P., & Pagonabarraga, I. (2018). Active microrheology in corrugated channels. The Journal of chemical physics, 149(17), 174908.
[11] Bain, N., & Bartolo, D. (2019). Dynamic response and hydrodynamics of polarized crowds. Science, 363(6422), 46-49.
[12] Truzzolillo, D., Sennato, S., Sarti, S., Casciardi, S., Bazzoni, C., & Bordi, F. (2018). Overcharging and reentrant condensation of thermoresponsive ionic microgels. Soft matter, 14(20), 4110-4125.
[13] Lattuada, E., Buzzaccaro, S. and Piazza, R., 2016. Colloidal swarms can settle faster than isolated particles: enhanced sedimentation near phase separation. Physical review letters, 116(3), p.038301.
[14] Parisi, G., Procaccia, I., Rainone, C. and Singh, M., 2017. Shear bands as manifestation of a criticality in yielding amorphous solids. Proceedings of the National Academy of Sciences, 114(22), pp.5577-5582.
[15] Jabbari-Farouji, S., Lame, O., Perez, M., Rottler, J. and Barrat, J.L., 2017. Role of the intercrystalline tie chains network in the mechanical response of semicrystalline polymers. Physical review letters, 118(21), p.217802.
[16] Berthier, L. & Ediger, M. Facets of Glassy Physics, Physics Today 69, 1, 40 (2016)
Coming soon.