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Bulletin of the American Mathematical Society

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Nonlinear dynamics of networks: the groupoid formalism

Authors: Martin Golubitsky and Ian Stewart
Journal: Bull. Amer. Math. Soc. 43 (2006), 305-364
MSC (2000): Primary 37G40, 34C23, 34C25, 92B99, 37G35
Published electronically: May 3, 2006
MathSciNet review: 2223010
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Abstract: A formal theory of symmetries of networks of coupled dynamical systems, stated in terms of the group of permutations of the nodes that preserve the network topology, has existed for some time. Global network symmetries impose strong constraints on the corresponding dynamical systems, which affect equilibria, periodic states, heteroclinic cycles, and even chaotic states. In particular, the symmetries of the network can lead to synchrony, phase relations, resonances, and synchronous or cycling chaos.

Symmetry is a rather restrictive assumption, and a general theory of networks should be more flexible. A recent generalization of the group-theoretic notion of symmetry replaces global symmetries by bijections between certain subsets of the directed edges of the network, the `input sets'. Now the symmetry group becomes a groupoid, which is an algebraic structure that resembles a group, except that the product of two elements may not be defined. The groupoid formalism makes it possible to extend group-theoretic methods to more general networks, and in particular it leads to a complete classification of `robust' patterns of synchrony in terms of the combinatorial structure of the network.

Many phenomena that would be nongeneric in an arbitrary dynamical system can become generic when constrained by a particular network topology. A network of dynamical systems is not just a dynamical system with a high-dimensional phase space. It is also equipped with a canonical set of observables--the states of the individual nodes of the network. Moreover, the form of the underlying ODE is constrained by the network topology--which variables occur in which component equations, and how those equations relate to each other. The result is a rich and new range of phenomena, only a few of which are yet properly understood.

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Additional Information

Martin Golubitsky
Affiliation: Department of Mathematics, University of Houston, Houston, Texas 77204-3008

Ian Stewart
Affiliation: Mathematics Institute, University of Warwick, Coventry CV4 7AL, UK

Received by editor(s): May 2, 2005
Published electronically: May 3, 2006
Additional Notes: Part of this material was presented by M. Golubitsky in the SIAM plenary lecture “Coupled cell systems: A potpourri of theory and examples", given at the Joint Mathematics Meetings in Phoenix, AZ, January 2004.
Article copyright: © Copyright 2006 American Mathematical Society
The copyright for this article reverts to public domain 28 years after publication.