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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 …
Francois Ziegler's user avatar
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 …
Francois Ziegler's user avatar
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) …
Francois Ziegler's user avatar
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 …
Francois Ziegler's user avatar
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 …
Francois Ziegler's user avatar
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.
Francois Ziegler's user avatar
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 …
Francois Ziegler's user avatar
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 …
Francois Ziegler's user avatar
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, …
Francois Ziegler's user avatar
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 …
Francois Ziegler's user avatar
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 …
Francois Ziegler's user avatar
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 …
Francois Ziegler's user avatar
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 $X$: …
Francois Ziegler's user avatar
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: " …
Francois Ziegler's user avatar
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).
Francois Ziegler's user avatar

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