Are robots the next condensed matter?

September 23, 2009
Modular robots on the march... Is this the next condensed matter?

Modular robots on the march... Is this the next condensed matter?

Because condensed matter deals with concepts as fundamental as as scale invariance and broken symmetry, it is sometimes hard to predict where the next big condensed matter physics problem will turn up. For example (continuing from my latest post) who would have guessed twenty years ago that atomic physicists and high-energy physicists would today be furnishing some of the most interesting examples of strongly correlated matter? So it is interesting to be wild and speculate where the next big realm of condensed matter physics may lay. (After all, wild speculation is one of the things a blog may be useful for.)

In this spirit, I dare suggesting a look at modular reconfigurable robotics: robots made up of many individual, but interacting, identical elements. There are a number of groups around the world working on it. At the time of writing, there is a fairly detailed overview of the field on Wikipedia.

The Wikipedia article list a number of challenges for the future. It starts with the following (I quote):

Demonstration of a system with >1000 units. Physical demonstration of such a system will inevitably require rethinking key hardware and algorithmic issues, as well as handling noise and error.

A way to phrase this problem is to say that we want a large assembly of robots to behave like a condensed matter system, where a very large collection of individual, interacting elements (e.g. all the individual atoms in a magnetic material) conspire to produce a collective behaviour (e.g. ferromagnetism) in spit of the presence of errors and imperfections (e.g. impurities, missing atoms at indivudal lattice sites, and so on). So in some sense this problem of modular reconfigurable robotics has already been solved by Nature in condensed matter systems. Thus some important problems in modular reconfigurable robotics might be solved by looking to condensed matter for inspiration (e.g. find the conditions to achieve in the robots the equivalent of generalised rigidity).

Indeed researchers in that field are already having to draw on some elementary condensed matter concepts. See, for example, the PARC Modular Robotics website: the section on the Proteo project even has a good old-fashioned discussion of close packing structures.

Conversely, and perhaps even more interestingly (at least from a condensed matter theorist’s point of view) the robots could be used to realize new states of classical condensed matter – just as novel forms of quantum condensed matter are currently being created through chemical synthesis and in ultra-cold atom labs. Interestingly, the individual building blocks in the case of robots can be a lot more complex than in any form of condensed matter we currently know of e.g. the rules governing element-element interactions may be very complicated – for example, the interactions could be time-dependent or depend on the history of previous interactions for each individual particle (i.e. each individual robot module). It will be interesting to see whether such complexity of the individual particles will find a manifestation at the collective (macro) level or rather we will find that the beahviour of the whole always obeys simpler, emergent organisational principles. The latter is the case of, for example, a human crowd – though the interactions between individual components of a human crowd are in fact simple, while in the case of robots we might engineer them to be very complex.

John Hubbard’s challenge 45 years on

September 22, 2009

A very brief Highlight feature we wrote some time ago on the complementarity between condensed matter and cold-atom experiments has now appeared on the ISIS website:

* J Quintanilla, C Hooley, ST Carr, JJ Betouras, VL Campo Jr and K Capelle, “John Hubbard’s challenge 45 years on”.

Strong correlations in ultra-cold atom gases and at the RHIC – the string connection

September 17, 2009

You may remember a brief mention of Brookhaven’s Relativistic Heavy Ion Collider (RHIC) in our article on strong correlations of a couple of months ago. This month Physics World carries another article, by Barbara Jacak, that discusses that type of strongly-correlated quantum matter in a lot more detail. The new article explains how string theory can be used to connect the experiments at RHIC to others carried out on another type of strongly-correlated system: ultra-cold atomic gases. Well worth reading:

PS: there was also a much more technical article on strongly interacting matter (as the quark-gluon soup is now known) in Rev. Mods. Phys. a few months ago:

Colloquium: Phase diagram of strongly interacting matter
P. Braun-Munzinger and J. Wambach, Rev. Mod. Phys. 81, 1031 (2009)