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Complex, contact, Riemannian, pseudo-Riemannian and Finsler geometry, relativity, gauge theory, global analysis.

3 votes
1 answer
377 views

A question about curvature for linear connections

Let $M$ be a manifold and $\pi : E \to M$ a rank $n$ vector bundle on $M$. We can define a connection on $E$ in two ways: We can specify the covariant derivatives $\nabla_X s$ or We can choose a co …
Daniel Barter's user avatar
1 vote
1 answer
840 views

A question about horizontal lifts for an Ehresmann connection

I was just reading the Ehresmann connection wikipedia page and noticed that it defines an Ehresmann connection to be complete if a curve in the base can be horizontally lifted over its entire domain. …
Daniel Barter's user avatar
2 votes

Distance metric on the unit sphere in R^3?

let $(M,g)$ be a Riemannian Manifold, let $ \gamma : [a,b] \rightarrow M$ be a piecewise smooth curve and let $\Omega : M \rightarrow \mathbb{R}^{n}$ be a coordinate chart. The length of $\gamma$ on t …
Daniel Barter's user avatar
4 votes
2 answers
6k views

Is an injective smooth map an immersion?

Suppose $M$ and $N$ are smooth manifolds. An immersion is a smooth map $f: M \rightarrow N$ whose pushforward is injective at each point. Is a smooth injective map an immersion? We can actually si …
Daniel Barter's user avatar
9 votes
1 answer
2k views

Is there a geometric proof for the upper semicontinuity of fiber dimension in algebraic geom...

One of the first theorems encountered in algebraic geometry is the upper semicontinuity of fiber dimension: Let $ f : X \to Y $ be a surjective regular map between irreducible varieties with irreduci …
Daniel Barter's user avatar
6 votes

Hessian as a tensor, multi-dimensional taylor series, and generalizations

Sorry for reviving this question. Everything Tom said is correct, but there is more to say about "coordinate-free Taylor series". It is true that arbitrary jet bundles $J^k(M,N)$ are subtle. The fib …
Daniel Barter's user avatar
2 votes

Breaking up the free Lie algebra into GL irreps

What you are describing is the algebraic operad Lie. More details can be found here. The Whitehouse modules are exactly what you get when you take Lie onto the other side of Schur Weyl duality. The s …
Daniel Barter's user avatar