Spiral waves are ubiquitous in two-dimensional systems of chemical or
biological oscillators coupled locally by diffusion. At the center of such
spirals is a phase singularity, a topological defect where the oscillator
amplitude drops to zero. But if the coupling is nonlocal, a new kind of spiral
can occur, with a circular core consisting of desynchronized oscillators
running at full amplitude. Here we provide the first analytical description of
such a spiral wave chimera, and use perturbation theory to calculate its
rotation speed and the size of its incoherent core.Comment: 4 pages, 4 figures; added reference, figure, further numerical test
