Active Matter

I first caught wind of Active Matter through the work of one of my favorite researchers, Tamas Vicsek, whose intellectual bling includes a fractal bearing his name.

My understanding of this sprawling sub-domain of physics is that we can study the activity of individuals agents and systems as though studying something like hydrodynamics, kinematics, and non-equilbrium statistical phsyics. Crowds become streams. Flocks become rivers. Networks of agents become oceans.

It is this vision of Active Matter that I’ll be discussing in this post, and on my site in general, but make no mistake of it, this field is awesome and sprawling, and worthy of a more extensive tour than I will ever be able to give.

Collective Motion

What governs the shape of a moving crowd leaving a moving theater? We know there’s not a central choreographer, and I don’t think we’d go so far as to say we have a genetic predisposition to filing out of a theater, so why is it we can identify patterns in crowd dynamics?

The interesting behavior outlined in Vicsek et al’s paper Novel Type of Phase Transition in a System of Self-Driven Particles is a phase transition as agents fall into sync. Just as there is a specific moment, a phase transition, from gas to liquid, there is a point of inflection in system. There are a lot of assumptions in the model though, including particles that maintain a constant absolute velocity, with an update to the average direction of neighbors in each time step. How are neighbors calculated (the range of perception)? Does doubt play a role?

Spiderwebs

I remember seing Tomas Saraceno’s spiderwebs in glass cubes at the SFMOMA and was struck by their archictectural beauty. Saraceno developed a scanning system to study the materiality of spiderwebs so that their learnings could be applied to art, architecture, and structural design. In discussing this work in Active Matter (edited by Skylar Tibbits), he shares an interesting idea pulled from Giorgio Agamben’s The Open: Man and Animal - “the two perceptual worlds of the fly and the spider are absolutely uncommunicating, and yet so perfectly in tune that we might say that the original score of the fly, which we can also call its original image or archetype, acts on that of the spider in such a way that the web the spider weaves can be described as ‘fly-like’“.

Speaking of The Open, in it Agamben describes the open with a nod to Rilke’s Duino Elegy, “the open, in which every being is freed … is being itself”. “For in the eighth Elegy it is the animal (die Kreatur) that sees the open ‘with all its eyes’, in distinct contrast to man, whose eyes have instead been ‘turned backward’ and placed ‘like traps’ around him”.