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Hamiltonian systems, symplectic flows, classical integrable systems
5
votes
Accepted
Embeddings of magnetic cotangent bundles over surfaces into closed symplectic 4-manifolds
This can always be done.
Let's first treat the case when $\Sigma$ is not a torus. Then take any symplectic $4$-manifold $(M,\omega)$ where $\Sigma$ can be embedded as a Lagrangian surface. Now, take a …
3
votes
Comparing the minimal Chern number and the cup-length of a symplectic manifold
I had a look at the paper of Givental, https://math.berkeley.edu/~giventh/papers/tor.pdf and don't see this statement... If this statement were true, Conjecture 6.1
of Eliashberg from 2015 would be …
6
votes
Contactomorphisms have in general no fixed points
I hope that the following answers some parts of the question.
1) a) It is not true that a generic contactomorphim doesn't have fixed points. For example, let $M$ be the three-dimensional torus that …
3
votes
Accepted
Hamiltonian $S^1$ actions with isolated fixed points
Nick Lindsay and have just proved that such a manifold indeed exists. And surprise, surprise, this is Tolman's manifold. See Theorem 1.3 and Corollary 1.4 of our paper: https://arxiv.org/abs/1912.027 …
2
votes
Accepted
Symplectic structure vanishing simultaneously on two totally real subspaces
I'll give a positive answer for two generic totally real planes in $\mathbb C^2$. I believe this generalises to larger $n$, though I don't prove it - just give a possible plan of a proof with one step …
2
votes
Large isometry groups of Kaehler manifolds
A positive answer to this question should follow from Berger's holonomy classification and the following statement, which I believe is correct:
Statement. For any dimension $n$ there exists a positi …
2
votes
Accepted
Star-shaped domain in $\mathbb{C}P^2$
One way to prove this is as follows.
First, from the assumption $B(1)\subset \mathbb C^2$ and the centre of $B(1)$ is $(0,0)$. Now we need the following two claims.
Claim 1. Any straight geodesic u …
9
votes
Accepted
Half-dimensional torus fibration vs Lagrangian torus fibration
This doesn't need to hold. For example, if one takes a $(T^4,\omega)$ with a constant symplectic structure $\omega$, in order for it to have a fibration by Lagrangian tori one should be able to find a …
3
votes
Accepted
Uniqueness of a compatible Kahler-Einstein structure on a symplectic manifold?
Concerning 2) one can, of course, take the product of two curves of higher genus to get a counter-example. In general, to have a statement as you want, one should look for rigid complex surfaces of ge …
5
votes
Accepted
Smooth projective toric varieties which are quotients of product of spheres and torii by a f...
Let us consider the case of toric varieties of real dimension $4$ and prove they
can not be represented as such a quotient unless they have second Betti
number $1$ or $2$.
Proof.
Let us introduce …
2
votes
Hamiltonian actions and contractible loops
There are counter-examples, hope they answer your question completely, just take
any non-simply connected $G$ and consider its action on $T^*G$. The simplest case is:
Let $M$ be the cylinder $S^1\tim …
9
votes
Reasons for the Arnold conjecture
In a certain sense, symplectic geometry (or safer to say symplectic topology) as we know it now was not existing before Arnold formulated these conjectures. So many would say that Arnold conjectures g …
2
votes
Accepted
Isometric embedding of a real-analytic Riemannian manifold in a compact Kähler manifold
I think the answer to your question should be positive and below is a sketch of what should work (I think).
Any real analytic manifold can be realised as the real part of a complex projective manifol …
14
votes
Accepted
How Many 4-Manifolds are Symplectic?
I have to apologize, in fact the answer to the second question is still unknown. Namely, up to now all known symplectic manifolds of dimension 4 that have negative Euler characteristic are blow ups of …
5
votes
Hyperbolic Coxeter polytopes and Del-Pezzo surfaces
I tried to investigate the question for some time and sent emails to several experts in the field. For the moment the conclusion seems to be the following:
The statement is well known to experts, was …