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Ehresmann connections; covariant derivatives; connections on vector bundles, principal bundles, ∞-bundles, submersions, bundle gerbes; holonomy and higher holonomy; parallel transport; torsion; curvature. See also the tags [principal-bundles], [vector-bundles], [gerbes], [curvature], [geodesics], [characteristic-classes], [torsion].

3 votes

Comparing holonomies along different connections?

The expression $\sigma_t=(1-t)\sigma+t\sigma'$ is a connection, for every $t \in \mathbb{R}$, giving a path between the holonomies.
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2 votes
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Definition of Connection as G-invariant splitting of a sequence which is a pulled back seque...

(Not how I think about principal bundles and connections, but certainly something Atiyah always does.) …
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4 votes

Existence of connections making a bundle endomorphism parallel

No. To be parallel under a connection, $N$ would have to have the same type at each point. In other words, for any two points, there must be a linear map identifying tangent spaces which identifies $N …
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5 votes

Two ways to differentiate a section of vector bundle

Yes: just write it out in a local basis: $\sigma_i = \sum f_{ij} E_j$ in some local choice of basis $E_j$, and $\sigma_1(p)=\sigma_2(p)$ means that $f_{1j}(p)=f_{2j}(p)$. Then $d(\sigma_1-\sigma_2)$ i …
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4 votes

Affine connections as equivariant maps

So I don't think you really don't get an action of the structure group of $FM^1 \to M$ on $S^2 \mathbb{R}^{n*} \otimes \mathbb{R}^n$ arising in this way: you are not making a difference between connections
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3 votes

Flat covariant derivative

Michael Spivak, A Comprehensive Introduction to Differential Geometry, volume II, p. 383, theorem 19, proves that the vanishing of curvature tensor of a Riemannian manifold implies flatness. But in fa …
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3 votes
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Splitting of higher order jet sequence

Look at the paper P. Jahnke and I. Radloff, Splitting jet sequences. They classify such splittings on compact Kaehler manifolds. Those which admit a vector bundle with splitting jet sequence are preci …
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3 votes
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Torsion free (1,0)-connections on the holomorphic tangent bundle?

Therefore if the $h_a$ form a partition of unity, for local choices of torsion-free $(1,0)$-connections, then $\gamma$ is a torsion-free $(1,0)$-connection. …
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6 votes

Why torsion is only defined for linear connection on TM?

So all connections look the same at a point, to first order. You can only feel that the connection is not flat at second order. …
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10 votes

Flat connection, finite-dimensional space of covariant constant one forms

The covariant constant 1-forms are parallel. The value of a covariant constant 1-form is determined throughout each connected component by its value at any one point: just take that value and parallel …
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1 vote
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Integrability condition for flat connections

On the manifold $X=U\times \operatorname{GL}_r$, with points written $x=(m,a)$, each tangent space $T_x X$ contains a linear subspace $V_x$ consisting of tangent vectors on which $a^{-1}da=-\omega'$. …
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11 votes

When are geodesics straight lines?

See Kobayashi and Nagano, On projective connections, Journal of Mathematics and Mechanics, vol. 13, no. 2, 1964. …
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4 votes
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Confusion about complex differential forms

Forget about vector fields $\partial_{z^{\mu}}$ and $\partial_{z^{\bar\mu}}$. Just think about 1-forms: $\omega^j_i = \Gamma^j_{i\mu}dz^{\mu}$, with $C^{\infty}$ functions $\Gamma^j_{i\mu}(z)$. Then i …
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3 votes

Aren't Riemannian geodesics also geodesics of the associated Cartan geometry?

The geodesics of Euclidean geometry in the plane are straight lines, i.e. curves that do not change direction. Their Cartan geometry is $$\omega=\begin{pmatrix}\gamma&\xi\\0&0\end{pmatrix}$$ on the or …
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28 votes

What is the Levi-Civita connection trying to describe?

I will try to help with the title question. I think that the real motivation for the Levi-Civita connection comes from looking at surfaces in Euclidean 3-space. Differentate one tangent vector field $ …
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