Questions tagged [geodesic]
A geodesic is a generalisation of the notion of a straight line to curved spaces, and can be sometimes be thought of as the locally shortest or extremal path between points.
1,257 questions
2 votes
0 answers
52 views
Is there a way to rewrite a differential equation to obtain uniqueness? Lipschitz
Motivation: I am trying to find and plot the Geodesics on the Torus, and obtained the following ODE: $$ \dot{\theta}(\varphi)=f_P(\theta) \qquad f_P(\theta)=\frac{1}{Pr}(R+r\cos\theta)\sqrt{(R+r\cos\...
4 votes
1 answer
58 views
Are the motion equations of an optimal control problem geodesics on a manifold?
Let us consider a Lagrangian system for which the equations of motion come from Hamilton's principle and are such that the control variable $\tau$ equals the equations of motion of a free system, ...
0 votes
0 answers
25 views
Finding the minimum distance path on the surface of an ellipsoid [duplicate]
Suppose I have the ellipsoid $$ \dfrac{x^2}{a^2} + \dfrac{y^2}{b^2} + \dfrac{z^2}{c^2} = 1 $$ And I have two points on this surface, $P_1 = (x_1, y_1, z_1)$, and $P_2= (x_2, y_2, z_2) $. I am ...
0 votes
0 answers
71 views
How do geodesics in 2D change under conformal change of the metric?
Let $g_{ij}$ be the components of a smooth 2D metric tensor with the quadratic line element $$ds_0^2 = g_{ij}\, dx^i \, dx^j = e^0 \cdot g_{ij}\, dx^i \, dx^j.$$ Perturb the metric into $$ds^2_\...
0 votes
0 answers
39 views
Geodesics on spheres (from Taylor’s classical mechanics) [duplicate]
I'm tying to find where I went Wrong in my efforts to solve problem 6.1 in Taylor’s book on classical mechanics. Using spherical polar coordinates $(r,\theta,\phi)$, show that the length of a path ...
1 vote
0 answers
30 views
Are $SO(n)$ and/or $SE(n)$ CAT spaces?
I am fairly new to the theory of CAT spaces, and I am trying to understand which familiar matrix spaces are CAT($\kappa$) for some $\kappa$. For instance, the space of real symmetric positive definite ...
4 votes
1 answer
119 views
If the Riemannian metric is known for each point along a curve, can you compute the parallel transport of a vector along the curve?
We have a curve in a Riemannian manifold $\gamma: [0,1] \to \mathcal{M}$. We know the Riemannian metric at each point $\gamma(t)$. Is this sufficient to do parallel transport of a vector along the ...
1 vote
0 answers
54 views
Do geodesics from an interior point intersect the boundary of a convex body only once?
Let $(M,g)$ be a Cartan-Hadamard manifold (simply connected, complete and with sectional curvature K≤0 ) and let $K \subset M$ be a closed convex body with $C^{1,1}$ boundary. Fix an interior point $p ...
3 votes
0 answers
41 views
Space that is strictly convex by balls but not strictly convex by distances
There are several notions of strict convexity for geodesic metric spaces. I showed that if $X$ is strictly convex by distances, then $X$ is strictly convex by balls. Proof. Let us fix $x,a,b \in X$ ...
1 vote
1 answer
58 views
In $\Bbb{R}^2\setminus\Bbb{D}^2$ with warped metric write the limit of θ-coordinate as the geodesic reaches the boundary in terms of initial data
In the manifold $$ M=\{x\in\mathbb{R}^2:\ |x|>a\}\quad(a>0), $$ you can write $M\cong (a,\infty)\times S^1$ with polar coordinates $(s,\theta)$ and take a conformal rescaling of the Euclidean ...
0 votes
0 answers
42 views
Geodesic on crescent-shaped 3-d uv-surface
How do you find the parametrization of the shortest curve between two points on the following surface: I am primarily interested in the parametrization r(t), more so than the length. Although ...
1 vote
1 answer
137 views
calculation discrepancy measuring arclength between points in Cartesian vs. spherical coordinates
I am calculating the length of an arc between two points on a sphere labeled in both Cartesian coordinates and spherical coordinates to confirm that my conversions and formulas are correct. I'm ...
3 votes
1 answer
145 views
What is the convention for notating geodesics in hyperbolic geometry?
Given the triangle in the Poincare model, would most mathematicians notate a side of the triangle $\overline{\text{BC}}$ or ? Basically, is there a standard convention based on function/visual ...
0 votes
0 answers
36 views
Is the Riemannian exponential locally bi-Lipschitz?
I was discussing with a friend and he said that the Riemannian exponencial is Locally bi-Lipschitz. But it is not clear to me why and I coundn't find this fact in any textbook. I tryied working it out ...
6 votes
1 answer
171 views
Flat torus defined by a lattice and minimal length of closed geodesics
I'm working on this exercise for my riemannian geometry course, but I’m a bit stuck. It's about the flat torus $T^2(v_1,v_2)=\mathbb R^2/\Lambda$ where $\Lambda=\mathbb Zv_1\oplus\mathbb Zv_2$. ...