Selection of the number of spiral arms in an optical pattern-forming system

This paper investigates the selection between target patterns and multi-armed spirals. This study shows that the selection between different spirals as well as the mere occurrence of target patterns arid spirals in the present experiment rely on the presence of radial phase gradients. Thus there does not seem to exist an intimate relation to target, patterns and spirals occurring in other systems which do not require inhomogeneous driving.