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Self-organization of active mixtures

Alberto Dinelli

Self-organization of active mixtures.

Rel. Alessandro Pelizzola, Julien Tailleur, Martin Lenz. Politecnico di Torino, Corso di laurea magistrale in Physics Of Complex Systems (Fisica Dei Sistemi Complessi), 2021

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Self-organization is ubiquitous in biological systems at all scales, from the animal world down to the intra-cellular environment. In all these systems, the dynamics of micro-constituents can lead to emergent large-scale behaviours, such as static patterns or collective motion. Active matter provides a solid framework to explain the physics behind these processes at many different scales. So far, the literature on the subject has mostly focused on single-component active systems; nonetheless, monodispersity imposes strong limitations on the complexity of the emergent macroscopic phases. In order to obtain less idealised self-assembling structures like the ones encountered in biology, heterogeneity must be included. In this work we study the macroscopic phenomenology of N-component active mixtures of run-and-tumble particles (RTPs) interacting via quorum-sensing (QS), with both numerical and analytical tools. Microscopic simulations are employed to study the macroscopic phases of binary active mixtures, with a special focus on dynamic patterns. To explain the emergence of the observed phases, we coarse-grain the microscopic theory to derive the macroscopic dynamics of the density fields. Via mean-field approximation and linear stability analysis of the field theory, we relate the microscopic parameters to the emergent large-scale patterns. Finally, we study under which conditions on the microscopic dynamics an active mixture of RTPs exhibits time-reversal symmetry (TRS) at the macroscopic level. When this occurs, the active mixture is macroscopically equivalent to an equilibrium passive system. In particular, we show that such a mapping to equilibrium can exist only if microscopic QS-interactions between different strains are reciprocal.

Relators: Alessandro Pelizzola, Julien Tailleur, Martin Lenz
Academic year: 2020/21
Publication type: Electronic
Number of Pages: 59
Corso di laurea: Corso di laurea magistrale in Physics Of Complex Systems (Fisica Dei Sistemi Complessi)
Classe di laurea: New organization > Master science > LM-44 - MATHEMATICAL MODELLING FOR ENGINEERING
Aziende collaboratrici: CNRS LPTMS
URI: http://webthesis.biblio.polito.it/id/eprint/19142
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