This function evaluates for with fixed and the differenital
It is calculated a corresponding Jacobi field
Since we can rewrite the problem as computing the differential of the reverted geodesic , this differential is computed using the differential of the start point of a geodesic.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 % xi = DxGeo(x,y,t,eta) Derivative of the geodesic(x,y,t) wrt y. % % % INPUT % x : start point of a geodesic, g(x,y,0)=x % y : end point of a geodesic, geo(x,y,1) = y % t : [0,1] a point on the geodesic to be evaluated, % may exceed [0,1] to leave the segment between x and y % eta : (in TyM) direction to take the derivative of. % % OUTPUT % xi : ( in Tg(x,y,t)M ) - DyGeo with respect to eta % --- % MVIRT R. Bergmann, 2017-12-04