[セミナー]第57回IPBセミナーを以下のように開催します。

[セミナー]第57回IPBセミナーを以下のように開催します。
日時：2024年11月26日（火）16：00-
場所：東大(本郷)理学部1号館445室 hybrid開催
講演者：Hugues Chaté 氏(CEA-Saclay, France & Beijing CSRC, China)
タイトル：Condensation and Synchronization in Aligning Chiral Active Matter
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http://statphys-ml.issp.u-tokyo.ac.jp/2024/11/statphys08303-utokyo-noneq-seminar-ipb.html

Abstract:
Spontaneous segregation of active matter into dense and sparse domains is
ubiquitous. In systems with local interactions, it is usually well
described as phase separation, and occurs not only in scalar active matter
(“motility-induced phase separation”) but also in vectorial, aligning
systems. This is in particular the generic situation for the simple but
important case of self-propelled particles locally aligning their
velocities against some noise. In such dry aligning active matter, the
order-disorder transition is not direct, and the homogeneous
orientationally-ordered liquid is generically separated from disorder by a
coexistence phase in which dense ordered regions evolve in a remaining
vapor.

We show that in collections of aligning circle swimmers with this phase
separation scenario is replaced by a condensation phenomenon. The
condensates, which take the form of vortices or rotating polar packets, can
absorb a finite fraction of the particles in the system, and keep a finite
or slowly growing size as their mass increases. Our results are obtained
both at particle and continuous levels. We consider both ferromagnetic and
nematic alignment, and both identical and disordered chiralities.
Condensation implies synchronization, even though our systems are in 2D and
bear strictly local interactions. We propose a phenomenological theory
based on observed mechanisms that accounts qualitatively for our results.