A Smooth Isotopy of Volume-preserving Diffeomorphisms on Unit Cube Saving Energy through Extra Dimensions
摘要
We construct an explicit example of a smooth isotopy {ξt}t∈[0,1] of volume- and orientation-preserving diffeomorphisms on [0, 1]n (n ≥ 3) that has infinite total kinetic energy. This isotopy has no self-cancellation and is supported on countably many disjoint tubular neighbourhoods of homothetic copies of the isometrically embedded image of (M, g), a “topologically complicated” Riemannian manifold-with-boundary. However, there exists another smooth isotopy that coincides with {ξt} at t = 0 and t = 1 but of finite total kinetic energy.