title: Front aggregation in multiarmed excitation vortices.
abstract: Using the Belousov-Zhabotinsky reaction, we study the pinning of multiarmed spiral waves to nonexcitable obstacles. With increasing obstacle size, the individual arms switch from a repulsive to an attractive state. This transition yields densely aggregated spiral arms and is caused by anomalous dispersion. A kinematic model reproduces the measurements quantitatively and identifies the transition as a supercritical pitchfork bifurcation.
authors.affiliation: Department of Chemistry and Biochemistry, Florida State University, Tallahassee, Florida 32306-4390, USA.
authors.forename: Brent T
authors.initials: BT
authors.lastname: Ginn
authors.forename: Oliver
authors.initials: O
authors.lastname: Steinbock