Questions tagged [connections]
In mathematics, a connection on a fiber bundle is a device that defines a notion of parallel transport on the bundle; that is, a way to "connect" or identify fibers over nearby points. (Def: https://en.wikipedia.org/wiki/Connection_(vector_bundle))
1,182 questions
4 votes
2 answers
144 views
Do affine connections always come from immersions in $\mathbb{R}^n$?
Consider $\mathbb{R}^n$ with its standard inner product and usual affine connection $\nabla^{\mathrm{eucl}}$. Let $M$ be a manifold and suppose that one is given an immersion $f:M\to\mathbb{R}^n$. At ...
-2 votes
0 answers
57 views
Exterior covariant derivative of a vector valued $k$-form [closed]
Given a connection on the tangent bundle $TM$ of $M$, how can we define an exterior derivative of a vector valued (with values in a vector bundle) $k$-form? Thank you for your answers.
0 votes
0 answers
44 views
Showing that the trace of the difference of the square of the curvatures of two connections on a vector bundle is exact
Let $E$ be a rank 2 complex vector bundle over a 4-dimensional manifold $X$. (I believe that the argument below does not depend on the rank of $E$ and the dimension of $X$.) I want to try to show, for ...
-1 votes
0 answers
82 views
Why is the connection necessary?
Let $M$ be a $n$-dimensional Riemannian manifold, i.e. $M = \cup_{\lambda \in \Lambda}\, (U_{\lambda}, g_{\lambda})$ with each $U_{\lambda}$ being an open ball around the origin of ${\Bbb R}^n$ and $...
0 votes
0 answers
54 views
Recovering the formula for curvature from matrix form using Cartan formalism
There is an old issue I couldn't fix by myself. I consider a manifold $M$, with frame bundle $E$, a flat and torsionfree affine connection $\nabla_0$ and an affine connection $\nabla$. I consider them ...
1 vote
1 answer
67 views
Flat connections and Lie-algebra homomorphisms from Der to End
I'm reading a classical paper by Katz and Oda on the Gauss-Manin connections, and I have question on one of its claims. Let $S$ be a smooth $k$-scheme and $\mathscr{E} \in \operatorname{QCoh}(S)$. Let ...
2 votes
1 answer
56 views
Meromorphic Connections on an Elliptic Curve
Let $E$ denote an elliptic curve over $\mathbb{C}$. I would like to consider meromorphic connections on the trivial line bundle $O_E^{\oplus r}$ with regular singularities occuring at some finite set ...
0 votes
1 answer
165 views
Levi-Civita connection for ${\mathrm{S}}^1$.
Let ${\mathrm{S}}^1$ be a circle with the radius $\frac{1}{2}$, which is a one-dimensional Riemannian manifold. I would like to give the chart on ${\mathrm{S}}^1$ by the affine $x$-real line and the ...
1 vote
1 answer
172 views
Line bundle and the ‘‘algebraic’’ Levi-Civita connection.
Let $P_{\Bbb C}^1$ be a projective line over the complex number field ${\Bbb C}$. We have $P_{\Bbb C}^1 \thickapprox S_{\Bbb R}^2$ as the Riemannian manifolds. There is the Levi-Civita connection on $...
0 votes
1 answer
69 views
Why are these two notions of Affine Connections equivalent?
There are two definitions of the affine connection on the tangent bundle of a $\mathcal{C}^\infty$ manifold $M$. One being in terms of a Differential Operator i.e. Definition: An Affine Connection is ...
0 votes
0 answers
54 views
Intrinsic derivative
In singularity theory, one defines an intrinsic derivative for a vector bunle homomorphism $\phi: E \rightarrow F$ where $E\xrightarrow{\pi_E}B$ and $F\xrightarrow{\pi_F}B$ are vector bundles with ...
2 votes
0 answers
50 views
Patching connections with partitions of unity preserves torsion?
In Section 10.2 of Loring W. Tu’s Differential Geometry: Connections, Curvature, and Characteristic Classes, he explains how to patch connections on a vector bundle using partitions of unity. He uses ...
1 vote
0 answers
64 views
Riemann Tensor with Torsion Intuition
I am trying to find an intuitive interpretation to the Riemann tensor in the presence of torsion. If we look at the index definition: \begin{equation} x^by^cR^a{}_{ bcd}z^d=x^by^c\left[\nabla_b,\...
1 vote
1 answer
48 views
Question about proof of proposition 10.2 in Nakahara's book $(R_{a*} X)^H = R_{a*}(X^H)$
This is about Nakahara's "Geometry, Topology and Physics", second edition, proposition 10.2. I am not understanding the simple statement at the very beginning of the proof. $$ (R_{a*} X)^H = ...
0 votes
0 answers
57 views
problem about connection in Lie group(solved)
I'm working on problem 4-11 of Lee's Introduction to Riemannian manifolds,here is it: Suppose $G$ is a Lie group. (a) Show that there is a unique connection $\nabla$ in $TG$ with the property that ...