BEGIN:VCALENDAR VERSION:2.0 PRODID:-//Talks.cam//talks.cam.ac.uk// X-WR-CALNAME:Talks.cam BEGIN:VEVENT SUMMARY:Spatial organisation in 3d active matter: from colloids to fish - Paddy Royall (ESPCI ParisTech) DTSTART:20231128T110000Z DTEND:20231128T120000Z UID:TALK208708@talks.cam.ac.uk DESCRIPTION:Fig. 1. Interactions and correlations in Active Matter. (a) Hy drodynamic coupling of Quince Rollerdumbbells to form an excited tetramer state [2\,3]. (b) Active labyrinth in self-propelled januscolloids [5]. (c ) Zebrafish as a tristable state: schooling\, milling and swaming.We prese nt results from three active matter model systems: Quincke Rollers (2d col loids) metaldielectric Janus particles (3d colloids) and zebrafish.In the bulk\, Quincke Rollers exhibit an intriguing phase behavior in which two r egimes ofmesophase separation similar to passive systems such as diblock c opolymers and short rangeattraction-long range repulsion systems are found . At low driving\, activity suppresses phaseseparation while at high drivi ng\, activity-induced banding leads to mesophase separation [1].Clusters o f Quincke Rollers exhibit a hierarchy of novel bound states\, reminiscent of excited stateis molecules\, only here the coupling is a combination of steric and hydrodynamic interactions [2\,3].In passive matter\, dimensiona lity has a profound effect upon phase behaviour. To realise 3d activecollo ids\, we use metal-dielectric Janus particles\, and explore their dynamics and phase behaviour.The latter is somewhat akin to a passive system of di polar colloids\, which forms an array ofpolymorphic colloidal crystal stru ctures. Beyond this already rich and complex behaviour\, the activesystem forms novel long-lived structures such as sheets and a labyrinthine phase [5].Finally\, we consider zebrafish. These are a convent and well-characte rised laboratory based modelsystem. Their bulk behaviour can be mapped ont o a modied Vicsek model with surprising accuracy[6]. Now the zebrafish can be tuned\, via genetic modification. We find that the Vicsek parametersfo r the modified zebrafish can be understood through the physiological chang e achieved throughthe gene change. Finally\, we show that just three zebra fish exhibit a tristable state and aresufficient to capture the many-body behaviour of much larger systems\, with only a weak change insystem proper ties as a function of size.[1] Mauleon-Amieva A\, Mosayebi M\, Hallett JE\ , Turci F\, Liverpool TB\, van Duijneveldt JS and Royall CP\,Phys. Rev. E 102 032609 (2020).[2] Mauleon-Amieva A\, Allen MP\, Liverpool TB and Royal l CP\, &ldquo\;Dynamics and Interactions of Quincke RollerClusters: from O rbits and Flips to Excited States&rdquo\;\, Sci. Adv. 9 eadf5144 (2023).[3 ] Schwarzendahl FJ\, Mauleon-Amieva A\, Royall CP\, Lö\;wen H\, Phys. Rev. E 107 054606 (2023).[4] Mauleon-Amieva A\, Liverpool TB\, Williams\, IP\, Souslov\, A and Royall CP ArXiV 2311.04288 (2023).[5] Sakaï\; N a nd Royall CP\, ArXiV 2010.03925 (2020).[6] Yang Y\, Turci F\, Kague E\, Ha mmond CL\, Russo J and Royall CP\, PLOS Comp. Biol. 18 e1009394 (2022).&nb sp\;\n \; LOCATION:Seminar Room 2\, Newton Institute END:VEVENT END:VCALENDAR