Sinklike spiral waves in oscillatory media with a disk-shaped inhomogeneity

Spiral wave propagation in oscillatory media with a disk-shaped inhomogeneity is examined. Depending on the properties of the medium as well as the inhomogeneity (different frequencies in two regions), distinct spiral waves including sinklike spirals and dense-sparse spirals, are able to emerge. We find that, unlike the previously found outward group velocity for spiral waves (normal spirals or antispirals), the direction of the velocity of the sinklike spiral wave points inward. A qualitative analysis of the possible mechanism underlying their formation is discussed, considering the inhomogeneity as a wave sink or source. Numerical simulations performed on other typical reaction-diffusion models confirm this analysis and suggest that our findings are robust and could be observed in experiments.