LPTMC Seminars

Motility regulation in active (eco)systems

Active matter describes systems whose constituents generate non-conservative forces on their environment, leading to the wealth of emergent phenomena encountered in the living world. In particular, the regulation of motility at the particle scale, either via external cues or quorum-sensing interactions with peers, can dramatically affect the self-organization of active systems.
In the first part of my talk, I will show how one can bridge the gap between particle-based dynamics and hydrodynamic descriptions of motility-regulated active systems, by deriving generalized Green-Kubo relations for a broad class of motility-regulated active systems. [1,2]
Building on these results, I will investigate the role of random motility regulation in the self-organization of microbial ecosystems consisting of N >> 1 species. Combining particle-based simulations with random matrix theory, I will show how weak, random interactions are sufficient to fragment the ecosystem into distinct, spatially segregated communities. Our results hold for a variety of motility-regulation mechanisms, and highlight the need to characterize the role of motility regulation in experimentally relevant situations. [3]

[1] AD, P. L. Muzzeddu, arXiv 2604.09447 (2026)
[2] AD, P. L. Muzzeddu, arXiv 2604.09453 (2026)
[3] AD, A. Altieri, J. Tailleur, Phys. Rev. E 114, 014404 (2026)

Quantum chaos and complexity in Krylov space

The dynamics of a quantum system is confined to a subspace of the state or operator space, the Krylov space, which is often smaller than the full Hilbert/operator space. Krylov space methods therefore provide a compact and computationally efficient description of quantum evolution, which is particularly useful for nonequilibrium phenomena in many-body systems with large Hilbert spaces. In this talk, I will discuss a notion of complexity defined in Krylov space and its use as a probe of operator growth, quantum chaos, information scrambling, and state evolution in both closed and open quantum systems. Illustrative examples include quantum spin chains, Sachdev–Ye–Kitaev models, and random matrix theory. The talk is based on selected topics from the review article arXiv:2405.09628 (Physics Reports) and more recent developments.