* 本帖最後由 iheby 於 2013-9-30 15:22 編輯 *
CN -> HK in a week
From http://math.stackexchange.com/qu ... an-chern-kcc-theory
The name 'KCC-theory' was introduced in a book of Antonelli, Ingarden and Matsumoto entitled The Theory of Sprays and Finsler Spaces with Applications in Physics and Biology published in 1993. It is mostly used in the physics and biology fields.
The KCC theory concerns the following. Consider a second order differential equation (d²xi/dt²)+gi(x,x′,t)=0, for i=1,...,n, where x=(x1,...,xn), t is the time parameter, x′ denotes ((dx1/dt),...,(dxn/dt)), and gi's are smooth functions of (x,x′,t) defined on a domain in the (2n+1)-dimensional Euclidean space. The aim is to understand what geometric properties of the system of integral curves - the paths associated with the system of differential equations - remain invariant under nonsingular transformation of the coordinates involved. The theory describes certain invariants, which are specific tensors depending on the gi's, which characterize the geometry of the system, in the sense that two such systems can be locally transformed into each other if and only if the corresponding invariants are equivalent tensors. In particular, a given system as above can be transformed into one for which the gi's are identically 0, so that the integral curves are all straight lines, if and only if the associated tensor invariants are all zero.
The problem may be viewed also as that of realising the integral curves of a second order differential equation as geodesics for an associated linear connection on the tangent bundle. Kosambi introduced a method using calculus of variations, which involves realizing the paths as extremals of a variational principle; this is related to finding a 'metric' for the path space.
By associating a non-linear connection and a Berwald type connection to the dynamical system, five geometrical invariants are obtained, with the second invariant giving the Jacobi stability of the system. |