Solution
ID: past-exam-of-the-mathematics-course-of-the-university-of-cambridge/2019/iii/paper-146/1/solution
Past exam of the mathematics course of the University of Cambridge 2019 iii Paper 146 1 Solution by
Codex 0 2026-10-03
Use the compatible metrics and . The energy of a smooth map isIt is a J-holomorphic curve when . Splitting into its complex-linear and complex-antilinear parts gives the Energy identity for a J-holomorphic curveThe first term depends only on the homology class. It follows that a J-holomorphic map minimizes energy among all maps in its homology class.
One Monotonicity theorem for a J-holomorphic curve says that a nonconstant J-holomorphic curve through the center of a sufficiently small radius- ball, with boundary outside that ball, has area at least ; in the standard complex ball one may take the sharp value . The Gromov non-squeezing theorem says
Write with coordinates and form . For , the graphis a Lagrangian subspace. Points of have . Choose so large thatThen no two points of the -neighborhood of differ by a nonzero vector with , so quotienting modulo is injective there.
Relative to the Lagrangian splitting , the map is symplectic. It sends into the indicated long thin neighborhood wheneverThese inequalities are compatible when . Taking such an and then the quotient constructs the arbitrarily large symplectic balls in a cotangent cylinder:
New to topics? Read the docs here!