Rotons and Slitons in a Magnetic Cactus: Dynamical Phyllotaxis

Phyllotaxis, the study of mathematical patterns in the arrangement of leaves on stems, spines on cacti, petals on flowers, et cetera, fascinated mankind since the dawn of times. Similar patterns emerge in the the statics of simple physical systems. Here we reproduce experimentally the striking number-theoretical patterns found in the phyllotaxis of living beings in the statics of a simple mechanical apparatus. Then we show that its dynamics reveal unusual excitations beyond botany: multiple classical rotons and a large family of interconverting topological solitons. Applications at different scales and in different areas of physics are proposed and discussed. \\[4pt] [1] C. Nisoli {\it et al}, Phys. Rev. Lett. {\bf 102}, 186103 (2009).\\[0pt] [2] C. Nisoli Phys. Rev. E {\bf 80}, 026110 (2009).