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Hamiltonian systems, symplectic flows, classical integrable systems

1 vote

Blowup and Delzant Polytope

This is Homework 22 in Ana Cannas da Silva's Lectures on Symplectic Geometry (2001). It's also described in her articles Symplectic toric manifolds (2003, p.124) and Symplectic Geometry (2006, p.172). …
Francois Ziegler's user avatar
1 vote
Accepted

Marsden–Weinstein: example of not proper action

(Comment $\to$ answer as requested.) Let $G=\mathbf R$ act on the 2-torus $Z=\mathrm U(1)\times\mathrm U(1)$ by $g(z_1,z_2)=(e^{ig}z_1, e^{i\pi g}z_2)$. Lift the action to $T^*Z$ and use any $G$-invar …
Francois Ziegler's user avatar
2 votes
Accepted

Kostant-Kirillov form versus Fubini-Study form on Plucker embedding

The answer is yes, due to formal properties of moment maps (that depend on almost no details of your situation). Namely, suppose $K$ acts transitively on any symplectic manifold $(X,\omega_X)$, with e …
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
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
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
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
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
4 votes
Accepted

When do commuting Hamiltonian flows have commuting generators?

This is not so much an answer as a suggestion to change the question. When $(P,\Omega)$ is prequantizable, i.e. there exists over $P$ a hermitian line bundle with connection $(L,\nabla)$ having curva …
Francois Ziegler's user avatar
3 votes
Accepted

Symplectic submanifolds of cotangent bundles of Lie groups

The preimage of a coadjoint orbit under a moment map is, under a mild transversality assumption, a coisotropic submanifold; so its null foliation $\smash{\ker(\omega_{|\Phi^{-1}(\mathcal O)})}$ is not …
Francois Ziegler's user avatar
2 votes

How are Poisson brackets and the variational principle related?

The direct connection between Poisson bracket and non-commutativity is pretty clear, at least if you agree that the (later introduced) Lie bracket $[X,Y]$ of vector fields measures the non-commutativi …
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
4 votes

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

I don’t think your characterization of the vector field is quite correct; I would recommend Cartan (1922, §§184-185), Godbillon (1969, Proposition XI.3.7), or Souriau (1970, Theorem 7.29). Or this ans …
Francois Ziegler's user avatar

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