לוח שנה משולב

Cells, tissues and organs can rotate spontaneously in vivo and in vitro. These motions are remarkable for their robustness and for their potential functions. However, physical mechanisms coordinating these dynamics are poorly understood. Active matter formalisms are required to understand these out-of-equilibrium phenomena with quantitative comparisons between theory and experiments.I will present two examples of spontaneous rotation with experiments synergized with theory (1, 2). In a first study (1), we report that rings of epithelial cells can undergo spontaneous rotation below a threshold perimeter. We demonstrate that the tug-of-war between cell polarities together with the ring boundaries determine the onset to coherent motion. The principal features of these dynamics are recapitulated with a numerical simulation (Vicsek model). In a second study (2), we show that cell doublets rotate in a 3D matrix and we identify mesoscopic structures leading the movement. Our theoretical framework integrates consistently cell polarity, cell motion, and interface deformation with equations capturing the physics of cortical cell layers. We also report that the Curie principle is verified in these cellular doublets with its symmetry relations between causes and effects. Altogether both examples could set generic rules to quantify and predict generic motion of tissues and organs as well as active synthetic materials.1- S. Lo Vecchio et al. Nature Physics 20:322–331(2024).2- L. Lu et al. Nature Physics 20:1194–1203 (2024).

Symplectic capacities are invariants that quantify the size of symplectic manifolds using themes from Hamiltonian dynamics and symplectic topology. While convexity is not preserved under symplectomorphisms, convex domains nevertheless exhibit notable behavior with respect to these capacities. Viterbo's volume-capacity conjecture (2000) suggests that, among convex domains of equal volume, the ball has maximal capacity. By capturing the interplay between convex and symplectic geometries, this simply formulated conjecture has become highly influential in the study of symplectic capacities, prompting extensive research. One result in this direction shows that smooth domains which are symplectic Zoll—a dynamical property—are local maximizers. In this talk, I will present a counterexample to Viterbo’s conjecture developed jointly with Yaron Ostrover and discuss follow-up questions. One implication is that a capacity maximizer cannot be smooth and strictly convex, raising the question of characterizing nonsmooth dynamical properties that detect local maximizers. I will propose a dynamical extension of the Zoll property to nonsmooth domains and discuss its equivalence with certain topological properties.

Nonreciprocal interactions in which the influence of A on B differs from that of B on A are abundant in physical, chemical, biological, and ecological systems, and are known to give rise to oscillatory states. Yet, it remains unclear whether these states represent true phases of matter: Can they maintain long-range order in spatially extended, noisy environments in the thermodynamic limit? And what kinds of phase transitions do they exhibit? To address these questions, we introduce a minimal generalization of the Ising model with two species having opposing goals. We demonstrate that oscillatory phases are stable in three dimensions but not in two, and that nonreciprocity changes the critical exponents from those of the Ising model to those of the XY model. We further extend this framework to a nonreciprocal XY model and develop a Harris-like criterion that determines when nonreciprocity fundamentally alters universal behavior. Finally, we apply these insights to a recent model of biomolecular condensates, predicting exotic dynamical phases and suggesting experimental tests.

perovskites are among the most promising materials for next-generation solar cells, offering exceptionalefficiency gains and driving major investment in large-scale production. Yet, as the technology moves toward realworlddeployment, corrosion has emerged as a critical but often overlooked challenge. It arises not only fromenvironmental exposure but also from the intrinsic reactivity of the perovskite itself, which can attack metalelectrodes such as gold through complex chemical pathways.This show highlights why corrosion in perovskite devices is both subtle and important. Light and heat can triggerchemical changes that produce reactive species, either directly corroding metals or transforming the perovskite intoa more aggressive state. By connecting principles from corrosion science and semiconductor physics, we revealhow these reactions originate and what must be done to control them at their source.

Dear colleagues,Attached is the flyer for our Demonstration & Training Seminar: Advanced NEW Technologies for Extracellular Vesicle Research, taking place on December 11th, 2025, Benozio Building, 2nd floor.The session will feature two new platforms at WIS:ZetaView Nanoparticle Analyzer (now available at WIS) – particle concentration, size measurements, zeta potential and fluorescence-based phenotyping.Exodus Bio automated EV-isolation systems – high-purity, reproducible EV isolation with minimal hands-on time.You are welcome to join onsite or online:https://us02web.zoom.us/j/86837215413?pwd=iRTFVP4C2ykvJspMsZ8b2cJj8r5oJl.1Looking forward to seeing you there,Avi

Satellite instruments, such as TROPOMI, are routinelyused to quantify tropospheric nitrogen dioxide (NO2)based on its narrowband light absorption in the UV/visible spectral range. The key limitation of suchretrievals is that they can only return the „verticalcolumn density“ (VCD), defined as the integral of theNO2 concentration profile. The profile itself, whichdescribes the vertical distribution of NO2, remainsunknown.This presentation showcases „NitroNet“, the first NO2profile retrieval for TROPOMI. NitroNet is a neuralnetwork, which was trained on synthetic NO2 profilesfrom the regional chemistry and transport model WRFChem,operated on a European domain for the month ofMay 2019. The neural network receives NO2 VCDs fromTROPOMI alongside ancillary variables (meteorology,emission data, etc.) as input, from which it estimates NO2concentration profiles.The talk covers:• an introduction to satellite remote sensing of NO2.• the theoretical underpinnings of NitroNet, how themodel was trained, and how it was validated.• practical new applications that NitroNet enables.

A fundamental theorem states that a two-dimensional Riemannian manifold with boundary, equipped with a symmetric tensor field, is locally isometrically embedded in Euclidean space if and only if the symmetric tensor field satisfies the Gauss-Mainardi-Codazzi equations—in which case, the tensor field is the second fundamental form.

When the intrinsic metric is Euclidean, it is a classical result that such tensor fields are Hessians of functions satisfying the Monge-Ampère equation. I shall present a version of this result to arbitrary Riemannian metrics, using a generalized Hodge theory I developed for a broader class of geometric boundary-value problems. I will discuss this theory, its main features, and perhaps give a glimpse of more complicated examples it addresses.

Living systems often operate at critical states – poised on the border between two distinct dynamical behaviours, where unique functionality emerges [1]. A striking example is the ear’s sensory hair cells, which amplify faint sounds by operating on the verge of spontaneous oscillations [2]. How such finely tuned states are maintained, and what statistical signatures characterise them, remain major open questions.In this talk, I will present a generic mechanism for critical tuning in population dynamics [3]. In our model, the consumption of a shared resource drives the population towards a critical steady state characterised by prolonged individual lifetimes. Remarkably, we find that in its spatially extended form, the model exhibits hyperuniform density correlations. In contrast to previously studied hyperuniform systems, our model lacks conservation laws even arbitrarily close to criticality. Through explicit coarse-graining, we derive a hydrodynamic theory that clarifies the underlying mechanism for this striking statistical behaviour. I will highlight several biological contexts in which this mechanism is expected to operate, including biomolecular complex assembly in the developing C. elegans embryo. Here, together with experimental collaborators, we identify signatures of critical tuning that may arise from resource competition.More broadly, our framework motivates future work on how living systems harness resource-mediated interactions to regulate their dynamical states.[1] T. Mora, W. Bialek, J Stat Phys (2011)[2] S. Camalet, T. Duke, F. Jülicher and J. Prost, PNAS (1999)[3] T Agranov, N. Wiegenfeld,O. Karin and B. D. Simons arXiv:2509.08077 (2025)FOR THE LATEST UPDATES AND CONTENT ON SOFT MATTER AND BIOLOGICAL PHYSICS AT THE WEIZMANN, VISIT OUR WEBSITE: https://www.bio