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

6 votes
Accepted

Pseudoholomorphic vector fields

I can give you a partial answer- a reformulation of your question. Perhaps others will then be able to give a counterexample. (I think it is not true in general.) Let's start from the beginning. A ma …
Spiro Karigiannis's user avatar
4 votes
Accepted

$L^2$ Hodge cohomology of ALE manifolds

I believe you can find this in the papers of Lockhart and McOwen. Specifically, check Lockhart, Robert B.; McOwen, Robert C. Elliptic differential operators on noncompact manifolds. Ann. Scuola Norm. …
Spiro Karigiannis's user avatar
2 votes

norm of $n$-th covariant derivative of smooth function

If $A$ is any section of a vector bundle $E$ over a smooth manifold $M$ and if $\nabla$ is any covariant derivative on $E$, then $\nabla A$ is a section of $T^*M \otimes E$, and this has a natural (po …
Spiro Karigiannis's user avatar
1 vote
Accepted

Hodge decomposition of a symplectic form.

Using the additional information that the OP provided in the comments to Yael Fregier's answer, I can elaborate as follows: I still don't know what "special complex manifold" means, but in any case, …
Spiro Karigiannis's user avatar
4 votes
Accepted

Paper about Sasaki-Einstein manifolds

Well, now there is a great textbook for Sasaki-Einstein geometry, by Boyer-Galicki: Sasakian Geometry. Here is a link to the book at Oxford University Press, DOI: 10.1093/acprof:oso/9780198564959.001. …
Spiro Karigiannis's user avatar
10 votes

Exterior derivative on almost complex manifolds

Just to follow up on Eric's correct answer: when you have an almost complex structure $J$, you can decompose $1$-forms into type $(1,0)$ and $(0,1)$. Locally, you can find a local basis $e^1, \ldots, …
Spiro Karigiannis's user avatar
9 votes

Flux through a Mobius strip

David Speyer already explained it very well. But if you want more details of the explicit calculations, you can look here: http://www.math.uwaterloo.ca/~karigian/teaching/multivariable-calculus/moebi …
Spiro Karigiannis's user avatar
4 votes
Accepted

How else can we describe the volume of a lagrangian submanifold in a Kahler manifold?

This is probably closer in spirit to what you're looking for than what you've received in the comments. If $(V^{2m}, J, \omega, g)$ is Calabi-Yau (which for me means that $J$ is integrable, and the fi …
Spiro Karigiannis's user avatar
23 votes
2 answers
6k views

Why are they called isothermal coordinates?

On a Riemannian manifold, a coordinate system is called "isothermal" if the Riemannian metric in those coordinates is conformal to the Euclidean metric: $$g_{ij} = e^{f} \delta_{ij}$$ My question is …
Spiro Karigiannis's user avatar
22 votes
4 answers
5k views

What is the best way explain to undergraduates that all 1-dimensional manifolds are orientable?

Let's suppose that $M$ is a connected $1$-dimensional smooth manifold (Haussdorf and paracompact). We know that there are exactly two types, up to diffeomorphism (even up to homeomorphism), namely $\m …
Spiro Karigiannis's user avatar
8 votes

reference for Noether's theorem

Another excellent book that does a proper job with Noether's Theorem is Peter Olver's Applications of Lie Groups to Differential Equations.
Spiro Karigiannis's user avatar
5 votes

Can a metric conformal to a Kahler metric be Kahler?

The paper by Apostolov, Calderbank, and Gauduchon that Francesco mentions find different Kaehler structures whose associated Riemannian metrics are conformal to each other. But they correspond to diff …
Spiro Karigiannis's user avatar
6 votes

book on calabi yau manifolds

I would also add the following book: Dominic Joyce, Compact Manifolds with Special Holonomy The early parts of the book include an introduction to the Riemannian geometry of Calabi-Yau manifolds. It …
Spiro Karigiannis's user avatar
1 vote

local kählerforms on complex manifold

(I decided to repost multiple comments as an answer. It's partly an answer if I understand the OP correctly.) I think the OP does not necessarily want to conclude that these "local" forms are the res …
Spiro Karigiannis's user avatar
5 votes

Hyper-complex and quaternionic Kähler Geometry

[First paragraph has been edited, after Vitali's comments below.] According to one convention, hyperKahler manifolds are not actually quaternionic-Kahler. This is the case if you define hyperKahler as …
Spiro Karigiannis's user avatar

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