TY - INPR A1 - Calin, Ovidium A1 - Der-Chen, Chang T1 - The geometry on a step 3 Grushin model N2 - In this article we study the geometry associated with the sub-elliptic operator ½ (X²1 +X²2), where X1 = ∂x and X2 = x²/2 ∂y are vector fields on R². We show that any point can be connected with the origin by at least one geodesic and we provide an approximate formula for the number of the geodesics between the origin and the points situated outside of the y-axis. We show there are in¯nitely many geodesics between the origin and the points on the y-axis. T3 - Preprint - (2004) 08 KW - Grushin operator KW - subRiemannian geometry KW - geodesics KW - Hamilton-Jacobi theory KW - elliptic functions KW - Euler's theta functions Y1 - 2008 UR - https://publishup.uni-potsdam.de/frontdoor/index/index/docId/2471 UR - https://nbn-resolving.org/urn:nbn:de:kobv:517-opus-26724 ER -