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Hamiltonian systems, symplectic flows, classical integrable systems

3 votes
Accepted

Are Gromov-Witten invariants birational invariants?

On a complex projective variety, Gromov-Witten invariants can be interpreted as virtual counts of curves, so they are biregular invariants. However, they are not birational invariant in general. The …
Francesco Polizzi's user avatar
7 votes

Is the mirror of a hyperkaehler manifold always a hyperkaehler manifold?

I think Verbisky proves a refined form of the Mirror Conjecture for hyperkaehler manifolds, not the conjecture in the strict form. This is explained at page 3 of the paper that you link. In fact, th …
Francesco Polizzi's user avatar
2 votes
Accepted

Computing the coefficients of the polynomial $\dim H^0(X,L^k)$ in non-smooth case

Sometimes one can at least compute $\chi(\mathcal{O}_X(X, \, L^k))$. The formula that one expects will be of the form "ordinary Riemann-Roch formula plus correction terms depending on the singularit …
Francesco Polizzi's user avatar
41 votes
Accepted

What is a Lagrangian submanifold intuitively?

Lagrangian submanifolds arise naturally in Hamiltonian Mechanics, because of the classical Arnold-Liouville theorem. Let me state it here: Theorem (Arnold-Liouville). Let $(M, \omega, H)$ be an inte …
Francesco Polizzi's user avatar
4 votes

Calculating the decomposition of a vector bundle over rational curve

Since you know the explicit equation of the conic, you can compute everything by using Macaulay2. The following script should be clear: i1 : k=ZZ/32003; i2 : ringP1=k[x, y]; i3 : ringP4=k[z1, z2, …
Francesco Polizzi's user avatar
8 votes
Accepted

Hyperbolicity for algebraic varieties and relation to curves on them

Take a very general hypersurface $j \colon X \hookrightarrow \mathbb{P}^n$ of sufficiently high degree, $3 \leq n \leq 4$. Then $X$ is Kobayashi hyperbolic (Kobayashi actually conjectured that this is …
Francesco Polizzi's user avatar
10 votes
Accepted

Why are the following varieties symplectomorphic?

In order to obtain an explicit description of the diffeomorphism, one can use the following argument. Take $B=\mathbb{C}^{n-1}$, with coordinates $t_1, \ldots, t_{n-1}$, and consider the complex spac …
Francesco Polizzi's user avatar