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Hamiltonian systems, symplectic flows, classical integrable systems

7 votes

Simple examples of Gromov-Witten invariants not being enumerative

I'm not sure if this is quite what you're looking for, but I always found it a useful example to keep in mind. Take the genus 1 invariant for degree 1 maps into $P^1$. There are no degree 1 holomorphi …
Jonny Evans's user avatar
  • 7,005
1 vote

Why are symplectic toric varieties projective?

Not a full answer, but a partial answer to your question 1a. Torus-invariant Kaehler metrics (in particular complex structures) were constructed by Guillemin, just starting with data on the moment pol …
Jonny Evans's user avatar
  • 7,005
2 votes
Accepted

Could this be a Hamiltonian symplectomorphism on a symplectic toric manifold

Sometimes it is, sometimes it isn't. The spheres living over the edges generate the second homology, so you can read off the action on $H_2$ from that. For $S^2\times S^2$ (square) the action on homol …
Jonny Evans's user avatar
  • 7,005
5 votes
Accepted

Progress on composition of Lagrangian correspondences/definition of symplectic categories?

Though not about solving the nontransversality problem, Fukaya's paper Unobstructed immersed Lagrangian correspondence and filtered A infinity functor is the state of the art in why nontransversality …
Jonny Evans's user avatar
  • 7,005
5 votes
Accepted

Question on Gromov-Witten invariants when $A=0$

In this case, the J-holomorphic curves are all constant, so the evaluation pseudocycle is the tridiagonal $\{(x,x,x) : x\in M\}$. You take cycles $A_1,A_2,A_3$ Poincare dual to $a_1,a_2,a_3$ respectiv …
Jonny Evans's user avatar
  • 7,005
5 votes
Accepted

Almost toric mutations

Mutation doesn't even change the integral affine base, which is why it doesn't change the symplectic manifold. All you're doing is changing the way the integral affine base is drawn. If you're given a …
Jonny Evans's user avatar
  • 7,005
3 votes

From Delzant polytope to lattice polytope

If you have a lattice polytope then you get a projective toric variety. If your polytope is not a lattice polytope then you can still construct a symplectic toric manifold (e.g. by performing symplect …
Jonny Evans's user avatar
  • 7,005
0 votes
Accepted

Maslov index equal to $2$ implies that the disk is not multiply covered

First, I assume you want $w$ to be holomorphic (or else it isn't true). If the target is really $S^2$ with boundary on the equator $L$ then this should be easy to prove directly. Take a point $p$ not …
Jonny Evans's user avatar
  • 7,005
4 votes
Accepted

$\mathbb{R}\mathbb{P}^n$ is monotone in $\mathbb{C}\mathbb{P}^n$, Lagrangian floer cohomology

The relative homology long exact sequence puts this group in between $H_2(\mathbb{CP}^n)=\mathbb{Z}$ and $\mathbb{Z}/2$. It maps surjectively to $\mathbb{Z}/2$. Let D be a generator for relative homol …
Jonny Evans's user avatar
  • 7,005
8 votes
Accepted

Cotangent bundles of surfaces as varieties

This is not possible. There is something called the growth rate of symplectic cohomology which is subexponential for affine varieties and exponential for cotangent bundles of higher genus surfaces (am …
Jonny Evans's user avatar
  • 7,005
2 votes
Accepted

Boundary Maslov index of holomorphic disks in Calabi-Yau manifolds

I assume you're asking about embedded or at least immersed discs, in order to make sense of the normal bundle. If so, let's fix an immersion $\iota\colon\Sigma\to M$ and observe that the pullback bund …
Jonny Evans's user avatar
  • 7,005
12 votes

Why believe Kontsevich cosheaf conjecture?

On the suggestion of DamienC, I'm converting my comments into an answer. I didn't do this before because I don't really know the answer to the deeper question of why the microlocal sheaf category is t …
Jonny Evans's user avatar
  • 7,005
5 votes

Infinity local systems

Since you tagged this with "symplectic geometry", I'm going to give an answer from a symplectic geometry perspective, which may not be what you're looking for, but (as a symplectic person) I find it i …
Jonny Evans's user avatar
  • 7,005
9 votes

How not to use J-holomorphic curves

One classic thing to do is to take a sequence of holomorphic curves with a tangency condition and assume that the tangency condition still holds in the limit: if the limit is a multiple cover with a b …
Jonny Evans's user avatar
  • 7,005
3 votes

Symplectic mapping class group and the "Lagrangian sphere complex"

I only just noticed this question, so maybe it's too late, but here's an answer. Note that some symplectic manifolds (like $\mathbf{CP}^2$) contain no Lagrangian spheres, so this complex is then empt …
Jonny Evans's user avatar
  • 7,005

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