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Complex, contact, Riemannian, pseudo-Riemannian and Finsler geometry, relativity, gauge theory, global analysis.
4
votes
Accepted
What does it mean for a space to be a differentiable stack?
Stacks form an (∞,1)-category. The latter informal notion has many equivalent implementations: simplicial category, topological category, quasicategory (also known as ∞-category), Segal category, com …
6
votes
Analogue of vector for differential operators
Yes. If $E→M$ and $F→M$ are vector bundles over a smooth manifold $M$, then differential operators $E→F$ of order less than $k≥0$ can be identified with sections of a finite-dimensional vector bundle …
3
votes
Germs of left invariant differential operators on a group
I presume “group” means “Lie group”.
Invariant differential operators on the Lie group $\def\R{{\bf R}}\R$ have the form $∑_{k≥0}a_k {∂^k\over ∂x^k}$, where $a_k∈\R$.
Thus, any linear differential dif …
7
votes
Accepted
A complex version of the Cahiers topos
This has already been done, see the article EFC-algebra and references therein.
In particular, the paper of Pridham constructs the topos of ∞-sheaves on the site of (derived) Stein spaces and explores …
3
votes
An identity for the higher form Levi-Civita connection
Both $m∘∇$ and $d$ are natural operations from $k$-forms to $(k+1)$-forms.
By Palais's theorem, all such operations are proportional to the de Rham differential.
That is, $m∘∇=λd$ for some $λ$.
By exa …
2
votes
Accepted
Regarding first order differential operator and derivative endomorphism
Substituting $f=f_1f_2$ in the definition of a derivative endomorphism immediately implies that $D_M$ is a derivation, using the fact that $g_1ψ=g_2ψ$ for all vector fields $ψ$ implies $g_1=g_2$, wher …
9
votes
Obstructions to the existence of a flat connection on a vector bundle
A $d$-dimensional flat real vector bundle $E→M$ is classified by a map $\def\B{{\sf B}}\def\GL{{\rm GL}}M→\B\GL(d)_δ$, where $\GL(d)_δ$ is the orthogonal group equipped with the discrete topology.
Arb …
3
votes
Accepted
Lie's third theorem via graded geometry
This is the Duistermaat–Kolk construction of a simply connected Lie group that integrates the given Lie algebra $\def\g{{\frak g}}\g$.
The starting observation is that for any simply connected Lie gro …
6
votes
Groupoid objects in the category of derived manifolds
Would this be of any interest to solve some geometric questions. Is there a notion of "derived stack" in the differential geometry setting.
The notion of a derived stack in the setting of differenti …
5
votes
Accepted
Holonomy as integration of curvature for principal $G$-bundles?
The curvature form descends to a genuine 2-form on the base space (unlike the connection 1-form). In fact, locally on the base space, we can pick a trivialization of the principal bundle and compute …
4
votes
Accepted
Connections on bundle gerbes from cocycle data
A gerbe on a manifold $M$ is a morphism of simplicial presheaves
$$\def\tB{{\sf B}}\def\U{{\rm U}}\def\cC{{\sf\check C}}\cC(U)→\tB^2\U(1),$$
where $\{U_i\}_{i∈I}$ is an open cover of $M$, $\cC(U)$ is …
4
votes
Accepted
Why is the transgression of differential forms a form?
After integration we have a number so isn't it a function?
Differential $k$-forms can be integrated along a submersion with $d$-dimensional fibers, which yields a differential $(k-d)$-form.
Fiberwis …
3
votes
What is the space of maps between superplane $\mathbb{R}^{0|2}$ and a smooth manifold $M$?
The manifold $\def\Hom{\mathop{\rm Hom}}\def\R{{\bf R}}\Hom(\R^{0|2},M)$ is isomorphic to the pullback of the parity-reversed bundle vector bundle $TM⊕TM$ along the projection map $TM→M$.
This is Lemm …
3
votes
references to learn the general theory Lie $\infty$-groupoids and Lie $\infty$-algebroids
There is no introductory book on Lie ∞-groupoids and ∞-algebroids analogous to Mackenzie's book.
The only book-length treatment that covers these subjects is Urs Schreiber's Differential cohomology in …
5
votes
Applications of “Homotopical algebra” in the set up of Lie groupoids
There are many connections between Lie groupoids and homotopical algebra. In recent years, a particularly prominent connection is to the theory of simplicial presheaves, originally developed in the c …