Seminars
The Theory Club seminar series
If you are interested, please contact ada.altieri@u-paris.fr to be added to the mailing list
09/07/24 - Giulia Pisegna
Emergent polar order in non-polar mixtures with non-reciprocal interactions
Phenomenological rules that govern the collective behaviour of complex physical systems are powerful tools because they can make concrete predictions about their universality class based on generic considerations, such as symmetries, conservation laws, and dimensionality. While in most cases such considerations are manifestly ingrained in the constituents, novel phenomenology can emerge when composite units associated with emergent symmetries dominate the behaviour of the system. I will present the study of a generic class of active matter systems with non-reciprocal interactions where we demonstrate the existence of true long-range polar order in two dimensions and above, both at the linear level and by including all relevant nonlinearities in the Renormalization Group sense. We achieve this by uncovering a mapping of our scalar active mixture theory to the Toner-Tu theory of dry polar active matter by employing a suitably defined polar order parameter. I will then show that the complete effective field theory of fluctuations -- which includes all the soft modes and the relevant nonlinear terms -- belongs to the (Burgers-) Kardar-Parisi-Zhang universality class. This classification allows us to prove the stability of the emergent polar long-range order in scalar non-reciprocal mixtures in two dimensions, and hence a conclusive violation of the Mermin-Wagner theorem. Finally, I will briefly show how to extend this dry system to a wet case, where hydrodynamic interactions are taken into consideration in the presence of a momentum-conserving fluid. The mapping to a polar active fluid is again crucial to uncover a fluid mediated linear instability for traveling waves.
18/06/24 - Aparna Baskaran
From molecules to moduli : Data driven approaches to controlling active nematics
This talk will describe recent attempts at building quantitative theories of active nematics guided by experimental data. Two examples will be considered - a confined 3D flow aligned fluid and a 2D bulk fluid. Further, some ongoing work on optimal control theory for control of active flows will be discussed.
17/06/24 - Anna Poggialini
Novel Approaches in Network Analysis and Dynamical Systems Modeling
In this talk, I will provide an overview of my recent research. The first part focuses on the main line of my thesis project, exploring network theory issues using the formalism of statistical mechanics.
The recent Laplacian renormalization group [1] has introduced a new perspective on treating networks within this framework, opening up several research avenues. Notably, we developed a community detection method that resolves information aggregation in networks at various resolutions [2]. We also investigated nodes that act as bottlenecks for temporal diffusion, proposing an alternative centrality measure. This measure connects with the fluctuation dissipation theorem, analogized with the Laplacian formalism.
Additionally, we identified new methods for detecting spectral dimensions, which under certain conditions, are related to the specific heat of graphs.
The second part briefly covers part of my research on dynamical systems. The project I would like to share aims to describe the dynamical effects of feed-forward and cyclic coupling structures in a modified Wilson-Cowan model.
[1] Villegas, P., Gili, T., Caldarelli, G. et al. Laplacian renormalization group for heterogeneous networks. Nat. Phys. 19, 445–450 (2023)
[2] arXiv:2301.04514
Full List of speakers ( from September 2023 )
14/06/24 - Serge Dmitrieff Pushing and pulling forces by actin : from microscopic to macroscopic models
11/06/24 - Nirbhay Patil Into the multiverse: Eigenvalue spectra of matrices of matrices
21/05/24 - Manon Michel Symmetries, conservation laws and (non-)reversibility
18/03/24 - Joël Mabillard Statistical mechanics of dissipative transport in systems with broken symmetries
08/03/24 - Ivan Palaia Shaping matter out of equilibrium: colloid assembly and membrane remodelling
07/03/24 - Deepak Gupta Optimal control of the F1-ATPase molecular motor
05/03/24 - Louise Budzynski Statistical mechanics of inference and optimization problems in high dimensions: application to spreading processes on random networks
04/03/24 - Pierre Barrat-Charlaix Eco-evolutionary dynamics of adapting pathogens and host immunity
29/02/24 - Cristóvão Dias Modeling Active Matter: from Newton’s mechanics to Machine Learning
27/02/24 - Jaron Kent-Dobias Where does a descending system come to rest? Ideas to revive a geometric answer
19/02/24 - Pratik Mullick Computational Strategies for Analyzing Collective Behavior in Human Crowds
12/02/24 - Efe Ilker Energetics of cellular processes and metabolic constraints in living organisms
06/02/24 - Loïc Marrec Evolutionary dynamics in subdivided populations
31/01/24 - Benjamin Guiselin Emergence of spontaneous collective oscillations in dense Human crowds
30/01/24 - Kailasham Ramalingam Dissipation as an organizing principle in soft materials: from polymers to active drops
24/01/24 - Valerio Sorichetti Transverse Fluctuations Control the Assembly of Semiflexible Filaments
17/01/24 - Arthur Genthon Non Equilibrium Transitions in Polymer Replication Accuracy
21/13/23 - Bertrand Lacroix-A-Chez-Toine Fluctuations of the ground-state energy for spherical spin-glasses
14/12/23 - Peter Olmsted How does the glass transition temperature in polymers depend on molecular weight?
11/12/23 - Francesco Mori Optimal control of living systems: from insect navigation to oscillating active fluids
05/12/23 - Alia Abbara Structured populations and other stories
22/11/23 - Tommaso Rizzo Mean-Field Theory of Kinetically Constrained Models
11/10/23 - Benoît Mahault Emergent organization and pattern formation induced by motility regulation
05/10/23 - Gustavo Lozano Dissipative Dynamics of Vortices and Domains in Nematic Superconductors
04/10/23 - Grzegorz Szamel Active matter: stochastic single active particle engine and emergent behavior in many-particle systems
27/09/23 - Marco Baity-Jesi Class Imbalance And Things That Look Like It
13/09/23 - Tristan Guyon Beyond translations in non-reversible sampling: general flows in Event-chain Monte Carlo
07/09/23 - Grant Rotskoff Tuning response with nonequilibrium control