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Complex, contact, Riemannian, pseudo-Riemannian and Finsler geometry, relativity, gauge theory, global analysis.
7
votes
Accepted
Does $(M\times M, \omega\times -\omega)$ admit a Lagrangian fibration?
No (independent of the full meaning of the question) in general it does not.
Any manifold which admits a Lagrangian fibration to a half dimensional base, also admits a Lagrangian foliation, and hence …
1
vote
Accepted
If the second derivative of a function on $\mathbb R^n$ is everywhere nondegenerate, does it...
The counter example given in the comments by Brian Conrad (and Dylan Thurston) is very nice. However, it oscillates wildly at $\infty$, and I believe that if you assume some nice properties at $\infty …
3
votes
Existence of Fermi coordinates on a Riemannian manifold
It is not enough to be within the injective radius. Let $(M,g)$ be an $(n+1)$-dimensional manifold and $\gamma\colon (-a,a) \to M$ a geodesic. One way to define Fermi coordinates
$\phi \colon (-a,a)\ …
5
votes
Diameter of a circle in an embedded Riemannian manifold
The answer to the first is NO.
As mentioned by another answer you can use Do Carmo to prove a local result of the type:
at points where the normal curvature is non-zero the 0-directions defines a fol …
3
votes
0
answers
267
views
Maps of loop spaces with infinity-bounded differential.
I am currently working with loop spaces of manifold and finite dimensional manifolds approximating these and the following comes up very naturally:
In the following piece-wise smooth means smooth on …
6
votes
Are there topological obstructions to the existence of almost quaternionic structures on com...
It seems to me that if I understood the comments to my comment correctly that the map
$$\mathrm{Sp}(1) \times \mathrm{Sp}(n) \to \mathrm{SO}(4n)$$
induced by right unit quarternionic multiplaction o …
12
votes
3
answers
3k
views
Are the stiefel-Whitney classes of the tangent bundle determined by the mod 2 cohomology?
Let $G=\mathbb{Z}/2\mathbb{Z}$. Let $f\colon L \to N$ be a smooth map of connected smooth closed $n$-dimensional manifolds such that the induced map
$$f^* \colon H^*(N,G) \to H^*(L,G)$$
is an isomor …
9
votes
0
answers
248
views
Parametrized cancelations in stable Morse theory
Let $B$ be a closed manifold. Let $\pi : M\to B$ be a submersion such that each fiber is a manifold without boundary. Let $f : M \to \mathbb{R}$ be a function such that the restrictions $f_x$ to each …