- Commit
- e650504db371aa9e0dce48f8c65ee01b4ce47fc9
- Parent
- 058d983138e4b97ff2cfd024e25441a39e2b4f02
- Author
- Pablo <pablo-escobar@riseup.net>
- Date
Changed the notation for the length function
Riemannian Geometry course project on the manifold H¹(I, M) of class H¹ curves on a Riemannian manifold M and its applications to the geodesics problem
Changed the notation for the length function
3 files changed, 10 insertions, 10 deletions
Status | File Name | N° Changes | Insertions | Deletions |
Modified | sections/applications.tex | 8 | 4 | 4 |
Modified | sections/introduction.tex | 4 | 2 | 2 |
Modified | sections/structure.tex | 8 | 4 | 4 |
diff --git a/sections/applications.tex b/sections/applications.tex @@ -493,7 +493,7 @@ however, is the following consequence of Morse's theorem. i : B^k \to \Omega_{p q} M \] of the unit ball \(B^k = \{v \in \RR^k : \norm{v} < 1\}\) with \(i(0) = - \gamma\), \(E(i(v)) < E(\gamma)\) and \(\ell(i(v)) < \ell(\gamma)\) for + \gamma\), \(E(i(v)) < E(\gamma)\) and \(L(i(v)) < L(\gamma)\) for all nonzero \(v \in B^k\). \end{enumerate} \end{theorem} @@ -535,15 +535,15 @@ however, is the following consequence of Morse's theorem. = E(\gamma) - \frac{1}{2} \delta^2 \sum_j \lambda_j \cdot v_j + \cdots \] we find that \(E(i(v)) < E(\gamma)\) for sufficiently small \(\delta\). In - particular, \(\ell(i(v))^2 \le E(i(v)) < E(\gamma) = \ell(\gamma)^2\). + particular, \(L(i(v))^2 \le E(i(v)) < E(\gamma) = L(\gamma)^2\). \end{proof} We should point out that part \textbf{(i)} of theorem~\ref{thm:jacobi-darboux} is weaker than the classical formulation of the Jacobi-Darboux theorem -- such as in theorem 5.5.3 of \cite{gorodski} for example -- in two aspects. First, we do not compare the length of curves \(\gamma\) and \(\eta \in U\). This could -be amended by showing that the length functional \(\ell : H^1(I, M) \to \RR\) -is smooth and that its Hessian \(d^2 \ell_\gamma\) is given by \(C \cdot d^2 +be amended by showing that the length functional \(L : H^1(I, M) \to \RR\) +is smooth and that its Hessian \(d^2 L_\gamma\) is given by \(C \cdot d^2 E_\gamma\) for some \(C > 0\). Secondly, unlike the classical formulation we only consider curves in an
diff --git a/sections/introduction.tex b/sections/introduction.tex @@ -51,8 +51,8 @@ we are interested is the infamous \emph{energy functional} \end{align*} as well as the \emph{length functional} \begin{align*} - \ell : H^1(I, M) & \to \RR \\ - \gamma & \mapsto \int_0^1 \norm{\dot\gamma(t)} \; \dt + L : H^1(I, M) & \to \RR \\ + \gamma & \mapsto \int_0^1 \norm{\dot\gamma(t)} \; \dt \end{align*} In section~\ref{sec:structure} we will describe the differential structure of
diff --git a/sections/structure.tex b/sections/structure.tex @@ -55,7 +55,7 @@ are the topologies induces by the norms \end{align*} respectively. -The problem with the first candidate is that \(\ell : {C'}^\infty(I, \RR^n) \to +The problem with the first candidate is that \(L : {C'}^\infty(I, \RR^n) \to \RR\) is not a continuous map under the uniform topology. This can be readily seen by approximating the curve \begin{align*} @@ -64,8 +64,8 @@ seen by approximating the curve \end{align*} with ``staircase curves'' \(\gamma_n : I \to \RR^n\) for larger and larger values of \(n\), as shown in figure~\ref{fig:step-curves}: clearly \(\gamma_n -\to \gamma\) in the uniform topology, but \(\ell(\gamma_n) = 2\) does not -approach \(\ell(\gamma) = \sqrt 2\) as \(n\) approaches \(\infty\). +\to \gamma\) in the uniform topology, but \(L(\gamma_n) = 2\) does not +approach \(L(\gamma) = \sqrt 2\) as \(n\) approaches \(\infty\). \begin{figure}[h]\label{fig:step-curves} \centering @@ -91,7 +91,7 @@ approach \(\ell(\gamma) = \sqrt 2\) as \(n\) approaches \(\infty\). The issue with this particular example is that while \(\gamma_n \to \gamma\) uniformly, \(\dot\gamma_n\) does not converge to \(\dot\gamma\) in the uniform -topology. This hints at the fact that in order for \(E\) and \(\ell\) to be +topology. This hints at the fact that in order for \(E\) and \(L\) to be continuous maps we need to control both \(\gamma\) and \(\dot\gamma\). Hence a natural candidate for a norm in \({C'}^\infty(I, \RR^n)\) is \[