Forced Snaking

We study spatial localization in the real subcritical Ginzburg-Landau equation ut = m0u + Q(x)u + uxx + d|u|u − |u|u with spatially periodic forcing Q(x). When d > 0 and Q ≡ 0 this equation exhibits bistability between the trivial state u = 0 and a homogeneous nontrivial state u = u0 with stationary localized structures which accumulate at the Maxwell pointm0 = −3d/16. When spatial forcing is included its wavelength is imprinted on u0 creating conditions favorable to front pinning and hence spatial localization. We use numerical continuation to show that under appropriate conditions such forcing generates a sequence of localized states organized within a snakes-and-ladders structure centered on the Maxwell point, and refer to this phenomenon as forced snaking. We determine the stability properties of these states and show that longer length scale forcing leads to stationary trains consisting of a finite number of strongly localized, weakly interacting pulses exhibiting foliated snaking.