Questions tagged [sg.symplectic-geometry]

Hamiltonian systems, symplectic flows, classical integrable systems

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7 votes
1 answer
377 views
+200

Goldman symplectic form vs Weil–Petersson symplectic form

I'm confused about the exact multiplicative factor that relates Goldman symplectic form on the $\operatorname{SL}(2,\mathbb R)$-character variety and the Weil–Petersson symplectic form on Teichmüller ...
3 votes
1 answer
83 views

Fredholm property of linearization of Floer map

I am reading Audin and Damian's book "Morse theory and Floer homology". In Proposition 8.1.4 which reveals the transversality property of moduli space of solutions of Floer equation, the ...
2 votes
1 answer
285 views

Sectional curvature and injectivity radius of natural metric in cotangent bundles

In the following paper by Cielibak, Ginzburg and Kerman (arXiv link, Comm. Math. Helv. 2004 DOI link) they claim in page $3$ that the natural metric $\tilde g$ on $T^*M$ the sectional curvature is ...
6 votes
1 answer
131 views

Symplectic diffeomorphism of the cylinder moving a point to 0

I am currently reading though part of Zehnder's Lectures on Dynamical Systems. In Chapter VII, I have found myself in the following situation: $Z(1)$ is a subset of standard symplectic space $(\...
3 votes
1 answer
272 views

Image of the moment map

Let $(M^{2n}, \omega ,\mathbb T)$ be non-compact symplectic manifold with an effective and Hamiltonian torus $\mathbb T$-action. Suppose its moment map $\mu$ is proper and the fixed point set of $\...
6 votes
3 answers
1k views

How is the Euler-Lagrange equation derived without local coordinates?

The Euler-Lagrange equation states that the time flow is given by a vector field such that the vector field contracted with the symplectic form gives dL, where L is the Lagrangian function on the ...
1 vote
1 answer
176 views

Special Darboux chart for tranverse Lagrangians

In the notes of Fukaya-Oh-Ohta-Ono (Lagrangian intersection Floer theory), Chapter 10 §54.1, it is stated: Let $L_{1}$ and $L_{2}$ be a pair of oriented Lagrangian submanifolds in $(M, \omega)$ that ...
4 votes
1 answer
117 views

Size of Hilbert space in geometric quantization from index theorem

In these notes on geometric quantization by Nair, on page 24, the Bohr-Sommerfeld rule in quantum mechanics is interpreted in terms of the Atiyah-Singer index theorem. To be precise, the polarization ...
2 votes
0 answers
135 views

Spectrum of an almost Hamiltonian matrix

I have a complex-valued block matrix $N=\begin{bmatrix} A & B \\ C & -A^* \end{bmatrix}$, where $A$ is diagonal, $B=B^*$, and $C$ is rank-1 but not Hermitian. If $C$ were Hermitian, $N$ would ...
2 votes
1 answer
109 views

Symplectic compatification of a cotangent bundle, or of a neighbourhood of its zero section

Take a closed manifold $\mathcal{L}$ and endow its cotangent bundle $T^*\mathcal{L}$ by the standard symplectic form $\omega = -d\lambda$, $\lambda$ being the Liouville form. I was wondering if it was ...
17 votes
4 answers
1k views

Can you tell the volume of a symplectic manifold from the Poisson brackets?

Suppose $(X^{2n},\omega)$ is a compact symplectic manifold. Knowing the algebra $C^\infty(X)$ is equivalent to knowing the manifold $X$, and knowing the Poisson bracket $\{\cdot,\cdot\}:C^\infty(X)\...
4 votes
0 answers
74 views

Pre-Symplectic Mapping

I have been studying symplectic integrators and their pre-symplectic extensions for dissipative systems. According to França, Jordan, and Vidal - On dissipative symplectic integration with ...
2 votes
1 answer
56 views

Displaceability of the sublevels below the Mane critical value

Recently I have been reading the paper "Symplectic topology of Mané's critical values" by Cielibak, Frauenfelder and Paternain. I am mostly interested in the part of the paper regarding the ...
0 votes
1 answer
216 views

How to express the Euler-Lagrange equation in arbitrary coordinates where $\omega \neq \sum dp_i \wedge dq_i$

I posted my questions in a previous post MO, but it seems that a more refined version for question on the Euler-Lagrange equation is needed. So, I post my question again. In standard symplectic ...
1 vote
0 answers
36 views

Displaceability questions in the symplectic 2-sphere for level sets of a Morse function

Consider the symplectic $2$-sphere $S^2$ with the canonical symplectic form $\omega$. A subset $A$ is called displaceable if there exists $H:S^2\rightarrow\mathbb{R}$ smooth such that $\Phi_H^{1}(A)\...
0 votes
1 answer
100 views

How does the symplectic form $\omega$ manifests itself in the Euler-Lagrange equation? + Extreme confusion with time

Let $\omega$ be a symplectic manifold on $\mathbb{R}^n$ and the smooth function $H : \mathbb{R}^n \times \mathbb{R}^n \to \mathbb{R}$ be a Hamiltonian. For $p,q \in \mathbb{R}^n$ let us assume that \...
1 vote
0 answers
64 views

Hyperkähler quotient of left $\operatorname{SU}(2)$-action on $(\mathbb{C}^2)^m \cong \mathbb{H}^m$

The natural $\operatorname{SU}(2)$-action on quaternions $\mathbb{H}\cong\mathbb{C}^2$ is hyperkähler. Extending it naturally to $\mathbb{H}^m$, one can make a hyperkähler quotient (where $\mu=(\mu_I,\...
0 votes
1 answer
163 views

Density of the set of convex polygons in the Banach-Mazur distance

Is the set of convex polygons dense in the set of convex domains in $\mathbb{R}^2$, for the Banach-Mazur distance? Any insight for a negative or positive answer is very much welcome!
4 votes
0 answers
120 views

Coulomb branches which are not of cotangent type

To each $3d \, N=4$ supersymmetric quantum field theory $\mathcal{T}$, there is a related space called the Coulomb branch of this theory, $\mathcal{M}_C(\mathcal{T})$ (it is a piece of the moduli ...
1 vote
1 answer
84 views

Derivative of the symplectomorphism evaluated at a point of the zero section of the cotangent bundle

It might be an easy question, possibly not worth posting here. In the proof of the Lagrangian neighborhood theorem, the authors have written the expression for the derivative of a symplectomorphism at ...
0 votes
0 answers
54 views

existence of moment maps for non-nef toric varieties

The noncompact toric variety $X_1 = \operatorname{Tot} \mathcal{O}(-1) + \mathcal{O}(-1) \to \mathbb{CP}^1$, the total space of the sum of two line bundles over the complex line, is defined as the ...
2 votes
0 answers
73 views

Can Coulomb branches have symplectic resolutions?

My question is about Coulomb branches of a $3D$ $\mathcal{N}=4$ supersymmetric gauge theory, in the sense of Bravermann, Finkelberg and Nakajima Towards a mathematical definition of Coulomb branches ...
2 votes
1 answer
200 views

Influence of symplectic invariants of the complement on being superheavy

Let $(M,\omega)$ be a symplectic manifold. I'm trying to show that a compact subset $K\subset M$ is $1$-superheavy [1, Definition 1.3] where $1=PD([M])$ is the unit in $QH^0(M)$. My question is: How ...
3 votes
1 answer
323 views

Coulomb branch varieties and symplectic singularities

I was recently looking at the survey article of Fu on symplectic resolutions which has a number of open questions and conjectures at the end. (I think one of these was existence of a classification ...
6 votes
1 answer
227 views

From time-dependent Hamiltonians to time-dependent symplectic/Poisson structures

Let $(M,\{.,.\})$ be a smooth Poisson manifold, and let $H\in C^\infty(M\times\mathbb{R},\mathbb{R})$. Question: Does there exist $H_0\in C^\infty(M,\mathbb{R})$ and smooth parameter-dependent Poisson ...
18 votes
2 answers
4k views

What is a Futaki invariant, what is the intuition behind it, and why is it important?

As the question title suggests, what is a Futaki invariant, what is the intuition behind it, and why is it important?
5 votes
1 answer
473 views

Definition of a moment map with physical context

This was originally posted on Math Stack Exchange, but without an answer. I thus move it here, and hope it's not because I express it unclearly. Suppose $(M,\omega)$ is a symplectic manifold "well" ...
6 votes
1 answer
226 views

Question about a remark on quantization of Coulomb branches

I will follow the definition of Coulomb branches of $3d$ $\mathcal{N}=4$ gauge theories from the paper by Braverman, Finkelberg and Nakajima, Towards a mathematical definition of Coulomb branches of 3-...
6 votes
0 answers
188 views

Does this pseudo-holomorphic triangle contribute to the product $\mu_2$ in Lagrangian Floer cohomology?

I'm computing the product map $$\mu_2 : CF(L_0,V)\otimes CF(V,L_1)\to CF(L_0,L_1)$$ in Seidel's exact triangle for this specific case: This is a genus 2 surface, and I color-coded the three (...
25 votes
1 answer
1k views

What can we say about the Cartesian product of a manifold with its exotic copy?

Let $M$ be a smooth oriented manifold, and let $M^E$ be an exotic copy, i.e homeomorphic but not diffeomorphic to $M$. Is it true that $M\times M$ is diffeomorphic to $M\times M^E$? I am ...
1 vote
1 answer
213 views

Question about the paper "Infinitely many monotone Lagrangian tori in del Pezzo surfaces"

In the paper "Infinitely many monotone Lagrangian tori in del Pezzo surfaces" by Renato Vianna, the author constructs an infinite amount of non-symplectomorphic monotone Lagrangian tori in ...
0 votes
0 answers
20 views

The effect that applying a nodal slide has on the fibers above the eigenline

So recently I've come across the following question posed to me by myself. Suppose I have an almost toric fibration that was obtained from a Delzant polyope by applying a nodal trade. Now in this ...
3 votes
1 answer
300 views

In which ways did geometric flows and variational methods from Riemannian geometry enter the symplectic world?

I am interested to learn about the role of geometric analytic methods for solving problems in symplectic geometry, In particular, I would like to know what results heavily rely on this machinery (incl....
1 vote
0 answers
37 views

Potential function in the smoothing of toric degenerations when not collapsing all $-2$-Spheres

In the paper "An-type singularity and nondisplaceable Lagrangian tori", https://arxiv.org/pdf/1710.11221.pdf, by Sun the author proves that when taking the toric degeneration of a semi-Fano ...
1 vote
0 answers
142 views

Invariants associated to a principal bundle whose total space is a symplectic manifold acted symplectically by group structure

The following question - proposal came to my mind about 4 years ago but I did not find any solution to this question and did not find any answer via e-personal comunication with some ...
1 vote
0 answers
114 views

Smooth action on cotangent space of the plane

Assuming that $S^1$ acts on $\mathbb{R}^2$ by smooth maps (which are diffeomorphisms), the induced action on the cotangent bundle given by $$g\cdot(x,\xi)=(g\cdot x,\varphi^∗_{g^{−1}}\xi)$$ acts via ...
1 vote
0 answers
56 views

Lagrangian Floer theory for negative monotone symplectic manifolds and Lagrangians

In the paper "Floer cohomology of Lagrangian intersections and pseudo-holomorphic Disks I", Oh shows that for a compact monotone Lagrangian $L$ in a closed monotone symplectic manifold $M$ ...
21 votes
3 answers
2k views

Proof of Giroux's correspondence

It is extensively used and cited the following statement due to Giroux: Given a closed $3$-manifold $M$, there is a $1:1$ correspondence between oriented contact structures on $M$ up to isotopy and ...
2 votes
0 answers
127 views

What is the topology on the space of differential forms $\Omega^2(M)$?

I have posted this question on MSE one year ago, but till now I did not received an answer. Therefore I have decided to post it here. I have difficulty in understanding the meaning of "A ...
17 votes
2 answers
2k views

Why Donaldson's Four-Six Conjecture?

Simon Donaldson apparently made the following conjecture: Two closed symplectic 4-manifolds $(X_1,\omega_1)$ and $(X_2,\omega_2)$ are diffeomorphic if and only if $(X_1\times S^2,\omega_1\oplus\omega)$...
1 vote
0 answers
171 views

Is the Poincare Birkhoff theorem valid if we change the volume form of the annulus region?

Is the Poincare-Birkhoff theorem valid if we change the volume form of the annulus region? Note: A possible approach could be the following: Is it true to say that the answer is affirmative ...
2 votes
0 answers
248 views

When is $f^*:T^*M\to T^*M$ an ergodic map for a diffeomorphism $f:M\to M$?

Let M be a differentiable manifold and $f:M \to M$ be a diffeomorphism. Then $f$ induces a natural map $f^* :T^*M \to T^*M$. The pull back map $f^*$ is a symplectomorphism wrt the ...
2 votes
1 answer
156 views

Is a simple J-holomorphic curve injective everywhere except for finitely many points?

Let $(M^{2n},J)$ be an almost complex manifold and $(\Sigma,j)$ a closed Riemann surface. Suppose $u: \Sigma \to M$ is a simple, nonconstant, $J$-holomorphic curve. Can we prove that the set $$ Z:=\{z\...
0 votes
0 answers
152 views

Structure maps of $\mathcal{A}_\infty$-bimodules

For Fukaya categories there are functors naturally induced by symplectomorphisms. Twisted versions of symplectic homology (fixed point Floer homology), open-closed maps and bimodules can be defined. ...
3 votes
0 answers
53 views

Complex structures compatible with a symplectic toric manifold

Let $(M^{2m},\omega)$ be a compact symplectic manifold with equipped with an effective Hamiltonian torus $\mathbb T^m$ action. Suppose $J_0$ and $J_1$ are two $\mathbb T^m$-invariant compatible ...
3 votes
1 answer
410 views

Integrability of Schroedinger's equation

Consider the periodic nonlinear Schrödinger equation $$-i \partial_t u + \Delta u = f(|u|)u, \qquad u=u(t,x) \in \mathbb{C}, \; t\in \mathbb{R}, \; x\in \mathbb{T}^n,$$ where $\mathbb{T}:= \mathbb{R}/\...
2 votes
0 answers
63 views

Why should we restrict the multiplicitiy of hyperbolic orbit to be one in Embedded contact homology?

Embedded contact homology(abbreviated by ECH) is a Floer type theory specially designed for three dimensional contanct manifolds(or generally, manifold with stable Hamiltonian structure) invented by ...
4 votes
0 answers
85 views

A couple of questions about the moduli space of annuli with some marked points on the boundary components

I'm trying to work out an answer for my previous question and I'm stuck with the following issue: In the paper Deformations of Bordered Riemann surfaces and associahedral polytopes by Devadoss, Heath ...
19 votes
3 answers
939 views

How big can a wedge of $n$ 2-forms in $\mathbb{R}^{2n}$ be?

$\def\RR{\mathbb{R}}$Let $\omega$ be a $2$-form on $\RR^{2n}$, where $\RR^{2n}$ has the usual Euclidean norm. The comass of $\omega$ is defined to be $\max_{|u|, |v| \leq 1} \omega(u,v)$. Here is the ...
14 votes
3 answers
4k views

Question about Hodge number

Hi. I am studying Hodge theory on Kahler manifolds. I have several questions. Is Hodge number a topological invariant? (I mean, is it independent of the choice of Kahler structure?) If the question ...

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