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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 …
11
votes
Manifolds distinguished by Gromov-Witten invariants?
Here is an answer to the REFINED question given to me by Richard Thomas.
In this refined version one looks for an example such that the cohomology
classes of two symplectic forms coincide.
In a late …
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
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 …