English

Toric degenerations and symplectic geometry of smooth projective varieties

Symplectic Geometry 2018-09-26 v3 Algebraic Geometry

Abstract

Let XX be an nn-dimensional smooth complex projective variety embedded in CPN\mathbb{C}\mathbb{P}^{N}. We construct a smooth family X\mathcal{X} over C\mathbb{C} with an embedding in CPN×C\mathbb{C}\mathbb{P}^{N} \times \mathbb{C} whose generic fiber is XX and the special fiber is the torus (C)n(\mathbb{C}^*)^n sitting in CPN\mathbb{C}\mathbb{P}^{N} via a monomial embedding. We use this to show that if ω\omega is an integral K\"ahler form on XX then for any ϵ>0\epsilon > 0 there is an open subset UϵXU_\epsilon \subset X such that vol(XUϵ)<ϵvol(X \setminus U_\epsilon) < \epsilon and UϵU_\epsilon is symplectomorphic to (C)n(\mathbb{C}^*)^n equipped with a (rational) toric K\"ahler form. As an application we obtain lower bounds for the Gromov width of (X,ω)(X, \omega) in terms of its associated Newton-Okounkov bodies. We also show that if ω\omega lies in the class c1(L)c_1(L) of a very ample line bundle LL then (X,ω)(X, \omega) has a full symplectic packing with dd equal balls where dd is the degree of (X,L)(X, L).

Keywords

Cite

@article{arxiv.1508.00316,
  title  = {Toric degenerations and symplectic geometry of smooth projective varieties},
  author = {Kiumars Kaveh},
  journal= {arXiv preprint arXiv:1508.00316},
  year   = {2018}
}

Comments

Revised in many places, applications to symplectic packing problem and lower bounds on Gromov width in terms of Newton-Okounkov bodies added, 26 pages, 1 figure