Johann Bernoulli Stichting voor de Wiskunde te Groningen

Johann Bernoulli lezing 16

(dinsdag 27 maart 2007)

Ian Stewart (University of Warwick)

All the World’s a Network

The talk will be highly illustrated and will avoid mathematical technicalities. It will describe some of the exciting research currently being done on the dynamics of networks, concentrating on applications to biology. Networks, and how they behave, have been propelled to the forefront of todays science. An epidemic is a disease that spreads through a network of people, linked by their contacts. The Internet is a network of computers, linked by phone lines. Mobile phones rely on a networks of base stations. Living creatures function because of networks of genes and their interactions, ecosystems are driven by predator-prey food webs, and the brain is a gigantic network of neurons. Even simple networks are remarkably versatile, and can be very puzzling. Scientists desperately need to understand how networks behave, but only recently have some of the basic principles been understood. A prominent example is the small world network, which explains old experiments showing that <91>six degrees of separation link any two people on the planet. The Kevin Bacon game (link actors together by films in which they have both played, with a link to Kevin Bacon as a final step) relies on the same phenomenon. The main focus of the talk will be on the dynamics of networks: patterns in the way they change over time. A good example is animal movement, where many different patterns can occur in the same animal. For instance, a horse can walk, trot, canter, or gallop. These patterns arise because of the form of the network of nerve cells that generates the basic rhythms. An unusual application is the formation of new species in evolution. Here a good example is "Darwin's finches" on the Galapagos Islands.

Laudatio: Jan van de Craats (Universiteit van Amsterdam)