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Riemannian Geometry is a subfield of Differential Geometry, which specifically studies "Riemannian Manifolds", manifolds with "Riemannian Metrics", which means that they are equipped with continuous inner products.

2 votes

Riemann's formula for the metric in a normal neighborhood

There is the following way of doing it. Let $\Gamma_{ijk}\equiv g_{is}\Gamma^{s}_{jk}$. Then (see here) $$ g_{jk}(x)=\delta_{jk}+\int_0^1 \alpha ~x^i\Gamma_{[ji]k}(\alpha x)~d\alpha $$ If we expand $\ …
dennis's user avatar
  • 521
3 votes
0 answers
203 views

Volume of sub-manifold of $\mathbf R^n$

Let $M$ be an $n-m$ dimensional sub-manifold of $\mathbf R^n$ defined by the following set of polynomial equations: \begin{equation} P_1(\vec x)=0, \\ \vdots \\ P_m(\vec x)=0, \end{equation} (where $\ …
dennis's user avatar
  • 521
4 votes
0 answers
227 views

To what extent is the Nash embedding not unique?

Consider a smooth Nash embedding, $f$, of a Riemannian manifold $Σ$ into Euclidean space $\mathbb R^n$. To what extent is this embedding not unique? It is clear that the set of all such embeddings con …
dennis's user avatar
  • 521
2 votes
1 answer
333 views

Volume of submanifold as integral of delta-function

Let $M$ be an $n-m$ dimensional sub-manifold of $\mathbf R^n$ defined by the following set of equations: \begin{equation} f_1(\vec x)=0, \\ \vdots \\ f_m(\vec x)=0, \end{equation} (where $\vec x$ are …
dennis's user avatar
  • 521
1 vote
2 answers
261 views

Ricci scalar of submanifold of $\mathbf R^n$

Let $M$ be an $n-m$ dimensional sub-manifold of $\mathbf R^n$ defined by the following set of equations: \begin{equation} f_1(\vec x)=0, \\ \vdots \\ f_m(\vec x)=0, \end{equation} where $\vec x$ are c …
dennis's user avatar
  • 521
0 votes

Ricci scalar of submanifold of $\mathbf R^n$

Thanks Willie but I find your answer slightly hard to follow. The following is what I uncovered. Given a basis $\{e_a\}$ (with $a=1,...,n-m$) for the tangent space $TM$ the second fundamental form, $\ …
dennis's user avatar
  • 521
2 votes
2 answers
380 views

Under what conditions can an orientable Riemannian 3-manifold be defined implicitly?

Under what conditions can an orientable Riemannian 3-manifold $\Sigma$ be defined implicitly? What I mean by implicitly is that there exists a smooth function $f:\mathbb{R}^n\to \mathbb{R}^m$, such th …
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  • 521