Hugues Chaté CEA-Saclay and Beijing CSRC
Long-range orientational order in 2D active matter
The birth of active matter physics may be traced back to 1995, when Tamas Vicsek and collaborators proposed to see collective motion as a spontaneously broken symmetry phase and introduced the now-famous Vicsek model. The same year, John Toner and Yuhai Tu, inspired by Vicsek, wrote down a field theory for this flying XY spin model, and obtained their landmark result: polar flocks can exhibit true long-range orientational order even in 2D.
I will first come back to these results and offer an updated view of such dry aligning dilute active matter (DADAM), where self-propelled point particles locally align their velocities in the presence of noise. I will then discuss some key facts and issues related to the various instances of long-range order presented by DADAM, including recent results showing that true long-range orientational order is also possible in 2D active nematics.
If time allows, I will discuss the robustness of the long-range ordered phases to various types of disorder.
Video of the lecture