Monads on projective varieties

We generalize Fløystad's theorem on the existence of monads on projectivespace to a larger set of projective varieties. We consider a varietyX, a linebundleLonX, and a basepoint-free linear system of sections ofLgiving amorphism to projective space whose image is either arithmetically Cohen-Mac...

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Veröffentlicht in:Pacific journal of mathematics 2018-05, Vol.296 (1), p.155-180
Hauptverfasser: Marchesi, Simone, Macias Marques, Pedro, Soares, Helena
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Sprache:eng
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Zusammenfassung:We generalize Fløystad's theorem on the existence of monads on projectivespace to a larger set of projective varieties. We consider a varietyX, a linebundleLonX, and a basepoint-free linear system of sections ofLgiving amorphism to projective space whose image is either arithmetically Cohen-Macaulay (ACM) or linearly normal and not contained in a quadric. Wegive necessary and sufficient conditions on integersa,bandcfor a monadof type $mathbf{0} rightarrowleft(boldsymbol{L}^{vee}right)^{a} rightarrow mathcal{O}_{X}^{b} rightarrow boldsymbol{L}^{c} rightarrow mathbf{0}$ to exist. We show that under certain conditions there exists a monad whosecohomology sheaf is simple. We furthermore characterize low-rank vectorbundles that are the cohomology sheaf of some monad as above.Finally, we obtain an irreducible family of monads over projective spaceand make a description on how the same method could be used on an ACMsmooth projective varietyX. We establish the existence of a coarse modulispace of low-rank vector bundles over an odd-dimensionalXand show thatin one case this moduli space is irreducible.
ISSN:0030-8730
0030-8730
DOI:10.2140/pjm.2018.296.155