A numerical solution of a generalized Swift-Hohenberg equation in two
dimensions reveals the existence of a spatio-temporal chaotic state comprised
of a large number of rotating spirals. This state is observed for a reduced
Rayleigh number ϵ=0.25. The power spectrum of the state is isotropic,
and the spatial correlation function decays exponentially, with an estimated
decay length ξ≈2.5λc, where λc is the critical
wavelength near the onset of convection. Our study suggests that this spiral
defect state occurs for low Prandtl numbers and large aspect ratios.Comment: LaTeX. 4 PostScript figures. Appende