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Durham e-Theses
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Distortion coefficients and exponential map in sub-Riemannian geometry

BORZA, SAMUEL (2021) Distortion coefficients and exponential map in sub-Riemannian geometry. Doctoral thesis, Durham University.

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Available under License Creative Commons Public Domain Dedication CC0 1.0 Universal.



The aim of this thesis is to explore the fields of sub-Riemannian and metric geometry.

We compute the distortion coefficients of the α-Grushin plane. These distortion coefficients are expressed in terms of generalised trigonometric functions. Estimates for the distortion coefficients are then obtained and a conjecture of a synthetic curvature bound for the $\alpha$-Grushin plane is proposed.

We then prove a version of Warner's properties for the sub-Riemannian exponential map. The regularity property is established by considering sub-Riemannian Jacobi fields while the continuity property follows from studying the Maslov index of Jacobi curves. We show how this implies that the exponential map of the Heisenberg group is not injective in any neighbourhood of a conjugate vector.

In the appendix, we prove that the curvature-dimension for negative effective dimension fails to hold in any strict and complete sub-Riemannian manifold.

Item Type:Thesis (Doctoral)
Award:Doctor of Philosophy
Faculty and Department:Faculty of Science > Mathematical Sciences, Department of
Thesis Date:2021
Copyright:Copyright of this thesis is held by the author
Deposited On:18 Oct 2021 12:14

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