Questions tagged [sg.symplectic-geometry]

Hamiltonian systems, symplectic flows, classical integrable systems

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Bubbling off a sphere in a splitting/stretching manifold

This question is related to my old question Bubbling off of a pseudo holomorphic sphere on surface with cylindrical ends about the bubbling off argument in Seidel's paper The symplectic Floer homology ...
Riccardo's user avatar
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Index of Floer operator for Hamiltonian vs Lagrangian Floer Homology

I am trying to see if there is a way to translate the computation of the index of the Floer operator for Hamiltonian Floer to Lagrangian Floer. Hamiltonian Floer homology is a theory that counts (...
Y.H. Chan's user avatar
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Obstructions to maximal number of independent constants of motion in a given symplectic manifold

Given a compact symplectic manifold $(X, \omega)$, are there any invariants (topological or easily computable geometric/analytic ones) which give an estimate of the maximal number of independent ...
user197284's user avatar
10 votes
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Simple examples of Gromov-Witten invariants not being enumerative

I understand why Gromov-Witten invariants in general are not enumerative, so it's not necessary to explain this. However to test something I'm working on, I'm looking for examples of concrete ...
user290289's user avatar
1 vote
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Seidel's calculation of the Floer cohomology of a cotangent fibre and its Dehn twist

I am reading Seidel's paper on exact Lagrangian submanifolds in $T^*S^n$ and the graded Kronecker quiver, and in Lemma 2 (2) he claims the following fact: if $F_0$ is a cotangent fibre and $F_1$ is $\...
B. S.'s user avatar
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Hamiltonian action as a group homomorphism

It is sometimes demanded that a Hamiltonian group action $G \times M \to M$ allow for a Lie algebra homomorphism from $\mathfrak{g}$ to $C^\infty(M)$ with the Poisson bracket. Is there a natural ...
MomentumMap's user avatar
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Connected components of Isotropy types as strata of Poisson leaves

Let $X$ be a smooth affine variety with an algebraic symplectic form $\omega$. Let $G$ be a finite subgroup of the group of symplectomorphisms of $X$. We can say that $X$ is trivially a normal variety ...
Flavius Aetius's user avatar
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Symplectic (or alike) integrator for system with Coulomb singularity and time-dependent potentials

I am trying to calculate classical trajectories for a single a ion and a single electron inside an RF trap. Therefore, I am dealing with a two-body system that possesses: Coulomb potential with a ...
michalt's user avatar
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In what topology does Gromov's lemma hold on noncompact symplectic manifolds?

In symplectic geometry, it is commonly said that ``the set of almost complex structures tamed to a symplectic form is contractible'' even on noncompact symplectic manifolds. In my understanding one ...
user500669's user avatar
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Symplectic quasi-states and displaceability of subsets of symplectic manifolds

In the paper "Quasi-states and symplectic intersections", Entov and Polterovich, introduced the notion of a partial symplectic quasi-state and used it the prove the following theorem: Let $(...
Someone's user avatar
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How to calculate the exterior derivative on manifolds of smooth mappings?

Let $S$ be a compact finite-dimensional manifold $S$ and $(M, \omega)$ a symplectic manifold. The space of smooth maps from $S$ to $M$, denoted by $\mathcal{M}$, has a canonical infinite-dimensional ...
Dorado Toro's user avatar
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Explicit Lagrangian fibrations of a K3 surface

I would like to look at the behaviour of the fibres of a Lagrangian fibration (such that at least some fibres are not special Lagrangian) $X\to\mathbb{CP}^1$ under the mean curvature flow (in relation ...
Quaere Verum's user avatar
2 votes
1 answer
201 views

Why are symplectic toric varieties projective?

Let $X$ be a symplectic toric manifold meaning a compact symplectic manifold $(X, \omega)$ with $\dim{X} = 2n$ equipped with a Hamiltonian action of a maximal-dimension torus $\mathbb{T} = (\mathbb{S}^...
Ben C's user avatar
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Weinstein's neighborhood theorem for exact symplectic manifolds

Let $(M, \omega)$ be a symplectic manifold and $L\subset M$ a Lagrangian submanifold. The Lagrangian Neighborhood Theorem says that there exists a neighborhood $U$ of $L$ in $M$ and a ...
Asier López-Gordón's user avatar
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Seeing $\mathbb{CP}^2 \mathbin\# \overline{\mathbb{CP}^2}$ as a symplectic reduction of different manifolds

I have been reading the paper "Remarks on Lagrangian intersections on toric manifolds" by Abreu and Macarini, which gives several non-displaceability results by avoiding the use of ...
Someone's user avatar
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What are known properties of the boundary curves of J-holomorphic curve with boundary

Suppose $\Sigma$ be a punctured Riemann surface with punctured boundary, and $(M, J)$ be a $2n$-manifold with almost complex structure $J$. Let $L$ be a totally real submanifolds of $M$ in smooth ...
ChoMedit's user avatar
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Deformation of a Liouville form with a diffeotopy

Let $M$ be a surface with boundary and let $f_t: M \to M, t \in [0,1]$ be a differentiable family of diffeomorphisms (I think this is usually called a diffeotopy). Suppose I have a Liouville form $\...
Eduardo de Lorenzo's user avatar
6 votes
1 answer
255 views

A geometric interpretation of the fractional Fourier transform

I was reading Joe Polchinsky’s autobiography which contains the following anecdote from his time at Caltech (page 18): Once a week, Feynman led Physics X, where freshman and sophomores could ask ...
Luke's user avatar
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Lagrangian cobordisms from a Legendrian knot to its scaled version

Having a Legendrian knot L in $\mathbb R^3$ and its scale aL (the length of Reeb chords of it are scaled by a>0), are these two Legendrians Legendrian isotopic? Maybe weaker, is there an exact ...
Anya Seaver's user avatar
2 votes
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Transformation of Morse function in $\mathbb{CP}^n$ trough symplectomorphism

I have a question I have been thinking for a while and feel like it should be true but have no idea of how to prove it. First let me introduce a piece of notation. Consider $(\mathbb{CP}^n,\omega)$ ...
kvicente's user avatar
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The homotopy type of the space of symplectic structures

While reading the book Introduction to the $h$-Principle by Y. Eliashberg and N. Mishachev, I noticed that the authors state, at the end of section 9.1.A, that the space of all symplectic structures ...
Akerbeltz's user avatar
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Is there a relation between symplectic toric orbifolds and semi-toric systems?

So recently I have been studying semi-toric systems which are a generalization of toric symplectic manifolds and allow for the presence of focus-focus fibers. These were proved to be classified by $5$ ...
Someone's user avatar
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6 votes
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Homology and cohomology of free loop spaces

String topology, as well as Hochschild (co)homology, give a rich perspective on the homology and cohomology of a free loop space $LM$ of a manifold $M$. Let $k$ be a field and let $M$ be $n$-...
skr's user avatar
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Question about symmetric bilinear form and convex geometry

Consider a Finsler norm $\varphi$ in $R^4$, and a positive definite symmetric bilinear form $S$, there also exists a vector-valued symmetric linear form $Q$, such that if $S(v, w) = 0$, then $Q(v, w)$ ...
threeautumn's user avatar
6 votes
1 answer
386 views

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

I am interested in Lagrangian correspondences in the context of symplectic manifolds, namely Lagrangian submanifolds $L_{12}$ of $M_1\times \bar M_2$ where $M_1$ and $M_2$ are symplectic manifolds ...
AlexArvanitakis's user avatar
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Question on the proof of doing a nodal trade, almost-toric fibrations

I am trying to understand the details of the proof of lemma $6.3$ of the following notes https://arxiv.org/pdf/math/0210033.pdf, which give us specific conditions of when we can swap a neighborhood of ...
Someone's user avatar
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Doing a nodal trade in a semi-toric system

Recently I have been studying semi-toric systems and almost toric fibrations. For the purpose of semi-toric fibrations I have been reading these notes https://arxiv.org/pdf/math/0210033.pdf. ...
Someone's user avatar
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Could this be a Hamiltonian symplectomorphism on a symplectic toric manifold

Suppose we have a sympletic toric manifold $(M,\omega)$ of dimension $4$ and let $\triangle$ be its corresponding Delzant polytope. Suppose that this polytope is "nice" enough so that we are ...
Someone's user avatar
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Neighborhood theorem for conical Lagrangian

Let $(M,\omega)$ be a compact $2n$ dimensional symplectic manifold and $T$ be a compact smooth $(n-1)$ dimensional manifold. Let $CT$ be the cone over $T$, i.e. $CT = T\times [0,1] / \sim $ where $\...
Soham's user avatar
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Doubt in the proof of Mcduff''s method of probes

I have been reading the paper "Displacing Lagrangian toric fibers by probes" by Dusa Mcduff, here is the arxiv link https://arxiv.org/pdf/0904.1686.pdf. I have a doubt in the proof of lemma $...
Someone's user avatar
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Overtwisted contact structures on $S^3$

All the isotopy classes of overtwisted contact structures are classified by the Hopf invariant. Are any of these contact structures contactomorphic? Suppose $d_{3}(\xi_{n}) = n$, then my guess is that ...
no_idea's user avatar
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Displaceability questions of fibers on integrable hamiltonian systems

Alot is known about the (non)-displaceability of the fibers of a toric symplectic manifold. For example there is Mcduff's method of probes to prove displaceability results using the moment polytope, ...
Someone's user avatar
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1 answer
157 views

Question about coadjoint orbits of compact connected Lie groups

Let $G$ be a compact Lie group with Lie algebra $\mathfrak{g}.$ Denote by $\mathfrak{g}^*$ the dual space of $\mathfrak{g}$. Let $r$ be an element of $\mathfrak{g}^*$ such that $G_r$ the stabilizer of ...
Mira's user avatar
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1 answer
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Question on Gromov-Witten invariants when $A=0$

I started trying to learn about Gromov-Witten invariants by reading the book "$J$-holomorphic curves and Symplectic Topology" and I have a doubt in an example the authors provide. It's ...
Someone's user avatar
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3 votes
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Is there an analogy of Austin-Braam approach to Bott-Morse type Hamiltonian Floer homology?

Austin-Braam approach uses the multicomplexes of de Rham complex on critical submanifolds to describe Bott-Morse theory. For more details, see the follows: https://link.springer.com/chapter/10.1007/...
ChoMedit's user avatar
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Relation between weight spaces of fixed loci of Hamiltonian $S^1$-actions

Consider an almost Kähler manifold $(M,\omega,I)$ with a $I$-(pseudo)holomorphic $\mathbb{C}^*$-action, whose $S^1$-part is Hamiltonian and the fixed locus $F=M^{S^1}$ is compact. Then, it breaks $F=\...
Filip's user avatar
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Weinstein fillings of a unit cotangent bundle

Given a closed, orientable manifold M, and its unit cotangent bundle $ST^{\ast}M$. I wonder under which conditions $ST^{\ast}M$ admits a subcritical Weinstein filling?
Alex Son's user avatar
4 votes
1 answer
114 views

Almost toric mutations

I'm trying to understand the details of the almost toric mutation process as explained in Section 8.4 in https://arxiv.org/pdf/2110.08643.pdf. More specifically, given an almost toric fibration $f: (M,...
cr1t1cal's user avatar
  • 755
3 votes
0 answers
115 views

Smooth handle attachment vs Weinstein handle attachment

Given a closed smooth manifold $M$ of dimension $n$, to which we attach a $k$-handle $H_k$. Take $T^{\ast} M$, can one realize $T^{\ast} (M\cup H_k)$ as a result of symplectic or Weinstein handle ...
Sergey Antonov's user avatar
7 votes
1 answer
475 views

Are holomorphic Lagrangians locally graphs?

Let $(M, \omega)$ be a holomorphic symplectic manifold of (complex) dimension $2n$. Let $x$ be a point in $M$. My understanding from the discussion and answers to this MO question is that there exists ...
Chris Schommer-Pries's user avatar
5 votes
0 answers
116 views

Isotopy classes of $CP^1$ in 4-manifolds

Let $S_1$, $S_2$ be homologous embedded 2-spheres in a compact smooth 4-manifold. Under which additional conditions are they smoothly isotopic? I am interested in the state of the art picture when $...
Misha Verbitsky's user avatar
1 vote
2 answers
237 views

Question about the Kähler structure on generic coadjoint orbits

Let $G$ be a compact connected Lie group. We denote by $\mathfrak{g}$ the Lie algebra of $G$ and by $\mathfrak{g}^*$ the dual space of $\mathfrak{g}$. Let $\mathcal{O}_r: = G\cdot r$ be a generic ...
Mira's user avatar
  • 129
2 votes
0 answers
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Manifold whose symplectic structure of the cotangent bundle is intrinsically different from any symplectic structure arising from $\mathbb{C}^n$

Inspired by this question Symplectic structure of $TS^{n-1}$ we ask: What is an example of a manifold $M$ whose cotangent bundle $T^*M$ is an Stein manifold but the canonical symplectic ...
Ali Taghavi's user avatar
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 ...
Mtheorist's user avatar
  • 1,135
6 votes
1 answer
524 views

Relation between symplectic (co)homology and Hochschild (co)homology and deformations

A very fluffy question in which I'm ignorant of homology/cohomology, grading etc: The open-closed and closed-open string maps relating the symplectic (co)homology and Hochschild (co)homology of the ...
86846515312's user avatar
6 votes
0 answers
210 views

Iterating exact triangles (particularly in Floer homology)

There are several different Floer-homological invariants of 3-manifolds (and knots). The most prominent of these are Heegaard Floer homology, monopole Floer homology, and instanton Floer homology. It ...
John Baldwin's user avatar
4 votes
2 answers
264 views

Realizing closed manifolds as Legendrian submanifolds of the standard contact vector space

I started learning some basic contact geometry, in particular its flexible side, and I got stuck with the following naive question. Given a closed manifold of dimension $n$, we can always embed it ...
Sam Lee's user avatar
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6 votes
1 answer
370 views

The norm-squared of a moment map behaves like a Morse-Bott function

Let $G$ be a compact Lie group with Lie algebra $\mathfrak{g}$. Let $<.,>$ denote a $G$-invariant inner product on $\mathfrak{g}$. Let $(M,\omega)$ be a symplectic compact manifold endowed with ...
Mira's user avatar
  • 129
1 vote
1 answer
93 views

Cotangent bundles to Riemannian manifolds and submanifolds

Let $N$ be a Riemannian manifold, and $\widetilde{N}\subset N$ a closed submanifold. If we look at the total spaces of the tangent bundles, we get that $T\widetilde{N}$ is a submanifold of $TN$. If ...
Johan's user avatar
  • 616
3 votes
1 answer
116 views

Holomorphic/Symplectic embedding of Riemann surfaces

Let $\Sigma_g$ denote a Riemann surface and let $X$ denote the complex surface $\Sigma_g \times \Sigma_g$. Then can there exist holomorphic embeddings of $\Sigma_l$ into $X$ for $l < g$? What about ...
cr1t1cal's user avatar
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