Definition:Variation Field of Family of Curves
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Definition
Let $M$ be a smooth manifold.
Let $\gamma$ be an admissible curve on $M$.
Let $I = \closedint a b$ is a closed real interval.
Let $J$ is an open real interval.
Let $\Gamma : J \times I \to M$ be the variation of $\gamma$, where $\times$ denotes the cartesian product and:
- $\ds \forall s \in J : \forall t \in I : \tuple {s, t} \stackrel \Gamma \mapsto \map \Gamma {s, t}$
Let $T_p M$ be the tangent space at $p \in M$.
Let $V : M \to T_\gamma M$ be a piecewise smooth vector field along $\gamma$ such that:
- $\map V t = \valueat{\dfrac {\partial \map \Gamma{s, t} }{\partial s}}{s \mathop = 0}$
Then $V$ is said to be the variation field of $\Gamma$.
Sources
- 2018: John M. Lee: Introduction to Riemannian Manifolds (2nd ed.) ... (previous) ... (next): $\S 6$: Geodesics and Distance. Geodesics and Minimizing Curves