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Non-reciprocity across scales in active mixtures.

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Dinelli, Alberto 
Curatolo, Agnese 


In active matter, particles typically experience mediated interactions, which are not constrained by Newton's third law and are therefore generically non-reciprocal. Non-reciprocity leads to a rich set of emerging behaviors that are hard to account for starting from the microscopic scale, due to the absence of a generic theoretical framework out of equilibrium. Here we consider bacterial mixtures that interact via mediated, non-reciprocal interactions (NRI) like quorum-sensing and chemotaxis. By explicitly relating microscopic and macroscopic dynamics, we show that, under conditions that we derive explicitly, non-reciprocity may fade upon coarse-graining, leading to large-scale equilibrium descriptions. In turn, this allows us to account quantitatively, and without fitting parameters, for the rich behaviors observed in microscopic simulations including phase separation, demixing, and multi-phase coexistence. We also derive the condition under which non-reciprocity survives coarse-graining, leading to a wealth of dynamical patterns. Again, our analytical approach allows us to predict the phase diagram of the system starting from its microscopic description. All in all, our work demonstrates that the fate of non-reciprocity across scales is a subtle and important question.


Acknowledgements: J.T. acknowledges the financial support of ANR Thema. A.D. acknowledges an international fellowship from Idex Universite de Paris. P.S. acknowledges support by a RSE Saltire Facilitation Network Award. Y.Z. acknowledges support from start-up grant NH10800621 from Soochow University.


38 Economics, 51 Physical Sciences, 3803 Economic Theory

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Nat Commun

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Springer Science and Business Media LLC
Agence Nationale de la Recherche (French National Research Agency) (THEMA)