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Hamiltonian systems, symplectic flows, classical integrable systems

4 votes
1 answer
1k views

A basic question related to Hamiltonian isotopy in symplectic geometry

In any standard symplectic geometry/topology textbook, the concept of Hamiltonian isotopy was introduced: $(M, \omega)$ is a sympplectic manifold. Given a symplectic isotopy $\phi_t : M \rightarrow M …
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4 votes
0 answers
189 views

Fibers of torus equivariant moment maps

Given a closed (possibly singular) projective variety $V$ with a symplectic structure and a torus action, there is a moment map $\mu: V \rightarrow Lie(T)^*$. Note that the dimension of $T$ could be …
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  • 1,719
0 votes
1 answer
376 views

Moment maps and flat degenerations of toric varieties

We have a flat family of projective varieties with a torus $T$ action, over $\mathbb{A}^1$. How do the moment map images of the fibers change when we pass from the generic fiber to the special fiber …
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  • 1,719
2 votes
1 answer
299 views

connectedness of fibers of torus-equivariant moment maps

Given a possibly singular, connected, symplectic algebraic variety with a torus action, every fiber of the moment map admits a torus action. Is each fiber of this moment map connected? Any examples or …
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  • 1,719
3 votes
1 answer
236 views

Singularity of torus fixed points from combinatorial data

May I ask what are the relations between the geometry and combinatorics near a torus fixed point? Any references? In particular, let $S$ be a scheme that is torus invariant with finitely many zero and …
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  • 1,719
7 votes
1 answer
710 views

Bialynicki-Birula Decomposition and moment polytopes/graphs

Let $X$ be a possibly singular projective scheme which admits a torus $T$ action and has finitely many $T$ fixed points and one-dimensional $T-$orbits. There are many such schemes in the Grassmannian/ …
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