English

Monads on projective varieties

Algebraic Geometry 2018-06-18 v1

Abstract

We generalise Fl\o{}ystad's theorem on the existence of monads on the projective space to a larger set of projective varieties. We consider a variety XX, a line bundle LL on XX, and a base-point-free linear system of sections of LL giving a morphism to the projective space whose image is either arithmetically Cohen-Macaulay (ACM), or linearly normal and not contained in a quadric. We give necessary and sufficient conditions on integers aa, bb, and cc for a monad of type 0(L)aOXbLc0 0\to(L^\vee)^a\to\mathcal{O}_{X}^{\,b}\to L^c\to0 to exist. We show that under certain conditions there exists a monad whose cohomology sheaf is simple. We furthermore characterise low-rank vector bundles that are the cohomology sheaf of some monad as above. Finally, we obtain an irreducible family of monads over the projective space and make a description on how the same method could be used on an ACM smooth projective variety XX. We establish the existence of a coarse moduli space of low-rank vector bundles over an odd-dimensional XX and show that in one case this moduli space is irreducible.

Keywords

Cite

@article{arxiv.1801.00151,
  title  = {Monads on projective varieties},
  author = {Simone Marchesi and Pedro Macias Marques and Helena Soares},
  journal= {arXiv preprint arXiv:1801.00151},
  year   = {2018}
}

Comments

22 pages, to appear in Pacific Journal of Mathematics

R2 v1 2026-06-22T23:32:55.742Z