Breakup of shearless meanders and "outer" tori in the standard nontwist map.
The breakup of shearless invariant tori with winding number omega=(11+gamma)(12+gamma) (in continued fraction representation) of the standard nontwist map is studied numerically using Greene's residue criterion. Tori of this winding number can assume the shape of meanders [folded-over invariant tori which are not graphs over the x axis in (x,y) phase space], whose breakup is the first point of focus here. Secondly, multiple shearless orbits of this winding number can exist, leading to a new type of breakup scenario. Results are discussed within the framework of the renormalization group for area-preserving maps. Regularity of the critical tori is also investigated.
Fuchss
K
K
Department of Physics and Institute for Fusion Studies, The University of Texas at Austin, Austin, Texas 78712, USA.
Wurm
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Apte
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Morrison
P J
PJ