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

1 vote

Invariant definition of the space of symbols on a vector bundle (pseudo-differential operators)

I think the following should work: Let $M$ be a compact manifold (just to be safe) and $\pi :E \to M$ a vector bundle. Since $E$ carries an action of $\mathbb{R}^{\times}$ there's an invariant notion …
Saal Hardali's user avatar
  • 7,799
5 votes
1 answer
259 views

What are the minimal local models for Riemannian manifolds? A local question about isometric...

There are many results about isometric embeddings of Riemannian manifolds but I haven't been able to find one that quite answers this question (which I believe must have some kind answer in the litera …
Saal Hardali's user avatar
  • 7,799
5 votes

What is torsion in differential geometry intuitively?

Let $M$ be a manifold and let $\nabla$ be a connection on its tangent bundle and let $(E, \tilde \nabla )$ be a vector bundle with connection. These two connections together extended uniquely to conn …
Saal Hardali's user avatar
  • 7,799
17 votes
1 answer
3k views

Integrals of pullbacks and the Inverse function theorem(s?)

The usual story goes like this: Smooth picture (?): For a smooth bijection $\phi: M \to N$ between $n$-manifolds the following is true: $\phi^{-1}$ is a local diffeomorphism a.e. …
Saal Hardali's user avatar
  • 7,799
6 votes
2 answers
1k views

A systematic canonical construction of the Hodge star operator

I'm struggling to make sense of the Hodge star as a global canonical object. Here are my struggles so far and some questions: Let $M$ be a finitely generated projective $R$-module (hence locally free …
Saal Hardali's user avatar
  • 7,799
6 votes
2 answers
1k views

Proof of the holomorphic Frobenius theorem in Voisin's book on Hodge theory (Theorem 2.26)

I'm trying to understand the proof of the holomorphic version of the Frobenius integrability theorem given in p. 51-52 of Voisin's text "Hodge Theory and Complex Algebraic Geometry I". Statement: …
Saal Hardali's user avatar
  • 7,799
16 votes
1 answer
2k views

A careful roadtrip from locally symmetric spaces to algebra

I'm trying to break the classification of locally riemannian symmetric spaces to little steps to make it more comprehensible (and s.t. the technical details can be verified without drowning completely …
Saal Hardali's user avatar
  • 7,799
6 votes
1 answer
591 views

Vector fields, diffeomorphism subgroups and lie group actions

Let $M$ be a compact smooth manifold. Since any vector field is complete we get a $1$-parameter subgroup for each vector field. Consider the following generalization: Let $\{X_j\} \in Vect(M)$ be a f …
Saal Hardali's user avatar
  • 7,799
7 votes
1 answer
2k views

Tangent bundle of a homogeneous space and the euler exact sequence

Let $H \subset G$ be a closed subgroup of a lie group and $G/H$ the homogeneous coset space. There's an exact sequence of adjoint representations of $H$: $$0 \to \mathfrak{h} \to \mathfrak{g} \to \ma …
Saal Hardali's user avatar
  • 7,799
9 votes
0 answers
376 views

Is there any notion of "smoothification" from $\mathbb{R}$-schemes to generalized smooth spa...

I will write $\operatorname{Diff}$ to denote a category of generalized smooth spaces e.g. $Sh(\mathsf{CartSp})$. Is there a version of $\operatorname{Diff}$ for which there exists a functor $\mathcal{ …
Saal Hardali's user avatar
  • 7,799
12 votes
2 answers
881 views

Representation viewpoint on Chern–Weil (cohomology computations done with rep theory?)

$\DeclareMathOperator\Sym{Sym}$Let $G$ be a compact lie group. Chern–Weil theory tells us that there's a homomorphism: $$H^{*}(BG;\mathbb{R}) \to (\Sym^{\bullet} \mathfrak{g^*})^G$$ which in our case …
Saal Hardali's user avatar
  • 7,799
3 votes
1 answer
224 views

"Canonical" form for gauge equivalence classes of matrices in $\mathfrak{gl}_n(x)$

Let $\mathfrak{gl}_n(x)= \mathfrak{gl}_n \otimes_\mathbb{C}\mathbb{C}(x)$ be the algebra of matrices taking values in rational functions. Definition: Two matrices $A, B \in \mathfrak{gl}_n(x)$ ar …
Saal Hardali's user avatar
  • 7,799
17 votes
0 answers
641 views

Is there an Infinite dimensional sheaf theory for analysis on manifolds?

I apologize if this question is slightly vague but I don't know how to ask it non-vaguely. Moreover, my question is about an ideal situation. If there's a close answer which doesn't satisfy all the co …
Saal Hardali's user avatar
  • 7,799
6 votes
1 answer
2k views

Transferring connection information to associated bundles and back

This might not be research level but I've tried more than once to ask about this in MSE and it got nowhere. So I thought It's fair to at least try. At the risk of repeating well known stuff I tried t …
Saal Hardali's user avatar
  • 7,799
18 votes
3 answers
4k views

What is an "Instanton" in classical gauge theory? (to a mathematician)

There's already a question about the same topic but I think its aim is different. Classical (non-quantum) gauge theory is a completely rigorous mathematical theory. It can be phrased in completely di …
Saal Hardali's user avatar
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