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Hamiltonian systems, symplectic flows, classical integrable systems
21
votes
Is there a high level reason why the inverse square law of gravitation yields periodic orbit...
There are:
Bertrand’s theorem, which says that the isotropic oscillator and Kepler potentials are the only analytic radial ones all of whose nonrectilinear bounded orbits are closed. (Recommendation …
19
votes
Accepted
Symplectic formulation of statistical physics
You want to read Chapter IV "Statistical Mechanics" in Structure of Dynamical Systems (1970 French original available here) by J.-M. Souriau, one of the pioneers of symplectic mechanics.
Given a symp …
18
votes
Accepted
Is a symplectic submanifold of a Kähler manifold Kähler?
No. In $\mathbf C^2$ with standard 2-form and complex structure, the real span of $U=\left(\begin{smallmatrix}1\\0\end{smallmatrix}\right)$ and $V=\left(\begin{smallmatrix}i\\1\end{smallmatrix}\right) …
12
votes
Darboux-like theorems
I think you have in mind the integrability (a.k.a. "flatness") problem for $G$-structures. Beyond the cases mentioned at that link (symplectic, Kähler, and complex structures, corresponding to $G=Sp(n …
10
votes
Information from Moment Polytopes
The difference $\frac12\dim(X)-\dim(T)$ is known as the complexity of the $T$-space (assumed effective), so that's the keyword you want to use. Such results as I've heard of are mainly for complexity …
8
votes
Can I bring the Kirillov 2-form on coadjoint orbits to adjoint orbits?
For $G$ semisimple as you assume, the Killing form gives a $G$-equivariant map $\mathfrak g\to\mathfrak g^*$, which identifies adjoint to coadjoint orbits. That is all you need.
7
votes
symplectic structure of tangent bundle of $\mathbb{S}^{n-1}$
$
\def\C{{\mathbf C}}
\def\d{\delta}
\def\e{{\mathbf e}}
\def\r{{\mathbf r}}
\def\u{{\mathbf u}}
\def\x{{\mathbf x}}
\def\y{{\mathbf y}}
\def\z{{\mathbf z}}
\def\<{\langle}
\def\>{\rangle}
$
If I unde …
7
votes
Special Cases of Duistermaat-Heckman Formula
Nice examples are worked out in Audin (2004, §VI.3.d), Arvanitoyeorgos (1999)(pdf), McDuff-Salamon (1998, §5.6). It’s not true that $\omega$ is rarely explicit: e.g. on all coadjoint orbits (including …
6
votes
Accepted
Level sets of Hamiltonians of S^1 actions
Michael F. Atiyah, Convexity and commuting Hamiltonians (1982), Lemma 2.3.
Dusa McDuff and Dietmar Salamon, Introduction to symplectic topology (2nd ed., 1998), Lemmas 5.51 and 5.54.
Michèle Audin, …
6
votes
Accepted
Compact simply-connected homogeneous symplectic manifold
Let your manifold be $X=G/H$. First of all, since it is simply connected, we can write it as $K/U$ where $K$ and $U=K\cap H$ are compact in $G$ (Montgomery’s theorem, 1950). Next, since $K/U$ is homog …
6
votes
Is every symplectic manifold a Hamiltonian reduction of a cotangent bundle?
That reminds me of a paper that I believe should answer your question: $\mathbf R^{2n}$ is a universal symplectic manifold for reduction (available here):
The authors show that if a manifold $Q$ i …
5
votes
Accepted
How to find Darboux coordinates?
There is a large literature on this. I would recommend the papers
MR0379752 Vergne, Michèle La structure de Poisson sur l'algèbre symétrique d'une algèbre de Lie nilpotente. Bull. Soc. Math. France …
5
votes
Accepted
Contradiction between fixed points of a hamiltonian diffeomorphism of a torus and quasi-peri...
1) is correct: by saying “hamiltonian diffeomorphism of” you imply that the torus has a symplectic structure $\omega$ and the diffeo is (something like) time 1 flow of a hamiltonian vector field $X$: …
5
votes
Deformation of Lagrangian manifolds
You already know that the pair $(M,L)$ of a symplectic manifold and a Lagrangian submanifold is locally isomorphic to $(T^*L, L)$. This is the beginning of Corollary 6.2 of Weinstein, who continues: " …
5
votes
Accepted
Flag manifolds as homogeneous Kahler manifolds
Flag manifolds $G/C(S)$ even exhaust homogeneous symplectic manifolds of $G$: Borel-Weil (1954, Thm 1). Also restated with fewer details in (1954, Thm 1).