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abstract: 'We compute the length of geodesics on a Riemannian manifold by regular polynomial interpolation of the global solution of the eikonal equation related to the line element $ds^2=g_{ij}dx^idx^j$ of the manifold. Our algorithm approximates the length functional in arbitrarily strong Sobolev norms. Error estimates are obtained where the geometric information is used. It is pointed out how the algorithm can be used to get accurate approximation of solutions of parabolic partial differential equations leading obvious applications to finance and physics.'
author:
- 'Jörg Kampen $^{1}$'
title: How to compute the length of a geodesic on a Riemannian manifold with small error in arbitrary Sobolev norms
---

Introduction
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Let $(M,g)$ is a Riemannian manifold, i.e. a differentiable $n$-dimensional manifold with a function $g$, which defines for all $p\in M$ a positive definite symmetric bilinear form $$g_p:T_pM\times T_pM\rightarrow {\mathbb R}$$ such that for any given vector fields $X,Y\in X(M)$ the map $$g(X,Y): M\rightarrow {\mathbb R},~p\rightarrow g(X,Y)(p):=g_p(X_p,Y_p)$$ is differentiable. The Riemannian metric $g$ allows to define a metric $d_M$ on $M$ via the length of curves $$d_M(x,y):=\inf_{\mbox{$\gamma$ diff.}}\left\lbrace L(\gamma)|\gamma :[0,1]\rightarrow M, \gamma(0)=x, \gamma(1)=y\right\rbrace,$$ with $$L(\gamma)=\int_0^1 \sqrt{g_{\gamma(t)}(\dot \gamma(t),\dot \gamma(t))} \,\mathrm dt.$$ With this definition any connected Riemannian manifold becomes a metric 