共查询到20条相似文献,搜索用时 0 毫秒
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LetX be a complex, connected, projective surface. LetL be a very ample line bundle onX, i.e. there is an embedding :X P
c
with
. In this article we study projective classification for surfaces when the independent variable is large. 相似文献
3.
Takeshi Kajiwara 《Archiv der Mathematik》2006,86(1):43-49
We show fundamental properties on embedding of abelian surfaces into projective toric 4-folds, and study the case of the toric
Del Pezzo 4-fold from the viewpoint of the moduli space of abelian surfaces with polarization of type (1, 5).
Received: 31 January 2005; revised: 15 April 2005 相似文献
4.
Numerically positive line bundles on a complex projective smooth algebraic surfaceS are studied. In particular for any such line bundleL Pic(S) we prove the following facts: (i)g(L) 0 and (ii)L is ample ifg(L) 1,g standing for the arithmetic genus. Some applications are discussed. We also investigate numerically positive non-ample line bundlesL withg(L)=2. 相似文献
5.
We study a Seshadri constant at a general point on a rational surface whose anticanonical linear system contains a pencil. First, we describe a Seshadri constant of an ample line bundle on such a rational surface explicitly by the numerical data of the ample line bundle. Second, we classify log del Pezzo surfaces which are special in terms of the Seshadri constants of the anticanonical divisors when the anticanonical degree is between 4 and 9. 相似文献
6.
Luis Fuentes García 《Archiv der Mathematik》2005,85(5):409-418
We reduce the problem of the projective normality of polarized abelian varieties to check the rank of very explicit matrices.
This allows us to prove some results on normal generation of primitive line bundles on abelian threefolds and fourfolds. We
also give two situations where the projective normality always fails. Finally we make some conjecture.
Received: 1 September 2004; revised: 10 March 2005 相似文献
7.
Federico Binda 《Journal of Pure and Applied Algebra》2018,222(1):61-74
In this note, we show that given a smooth affine variety X over an algebraically closed field k and an effective (possibly non-reduced) Cartier divisor on it, the Chow group of zero cycles with modulus is torsion free, except possibly for p-torsion if the characteristic of k is . This generalizes to the relative setting classical results of Rojtman (for X smooth) and of Levine (for X singular). 相似文献
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Let X be a complex connected projective nonsingular algebraic surface endowed with an ample line bundle L, which is spanned by its global sections. Pairs (X, L) as above, with sectional genus g(X, L)=1+(L·(K
X
L))/2=3 are classified by means of the main techniques of adjunction theory. 相似文献
10.
We study the geometry of the birational map between an intersection of a net of quadrics in
that contains a line and the double sextic branched along the discriminant of the net. We show that the branch locus of a
smooth double sextic S
6 is discriminant of a net of quadrics in
such that S
6 is isomorphic to the intersection of this net iff a certain configuration of rational curves on S6 is weakly even.
Received: 14 September 2005
Suported by the DFG Schwerpunktprogramm ‘Global methods in complex geometry’. The first named author is partially supported
by the KBN Grant No. 1 P03A 008 28. The second named author is partially supported by the KBN Grant No. 2 P03A 016 25. 相似文献
11.
Sam Payne 《Mathematische Zeitschrift》2006,253(2):421-431
We show that the dual of the cone of divisors on a complete -factorial toric variety X whose stable base loci have dimension less than k is generated by curves on small modifications of X that move in families sweeping out the birational transforms of k-dimensional subvarieties of X. We give an example showing that it does not suffice to consider curves on X itself.
Supported by a Graduate Research Fellowship from the NSF 相似文献
12.
In this paper, we investigate whether the 124 nonsingular toric Fano
4-folds admit totally nondegenerate embeddings from abelian surfaces or
not. In consequence, we determine the possibilities of these embeddings,
except for the remaining 18 nonsingular toric Fano 4-folds.
Received: 12 July 2002 相似文献
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Working over , we show that, apart possibly from a unique limit point, the possible values of multi-point Seshadri constants for general points on smooth projective surfaces form a discrete set. In addition to its theoretical interest, this result is of practical value, which we demonstrate by giving significantly improved explicit lower bounds for Seshadri constants on and new results about ample divisors on blow ups of at general points. 相似文献
15.
Daisuke Matsushita 《Mathematische Zeitschrift》2008,258(2):267-270
Let X be a projective irreducible symplectic manifold and L be a non trivial nef divisor on X. Assume that the nef dimension of L is strictly less than the dimension of X. We prove that L is semiample.
Partially supported by Grant-in-Aid no. 15740002 (Japan Society for Promotion of Sciences) 相似文献
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Let
be a very ample vector bundle of rank two on a smooth complex projective threefold X. An inequality about the third Segre class of
is provided when
is nef but not big, and when a suitable positive multiple of
defines a morphism X → B with connected fibers onto a smooth projective curve B, where KX is the canonical bundle of X. As an application, the case where the genus of B is positive and
has a global section whose zero locus is a smooth hyperelliptic curve of genus ≧ 2 is investigated, and our previous result
is improved for threefolds.
Received: 27 January 2005; revised: 26 March 2005 相似文献
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Let L be an ample line bundle on a K3 surface. We give a sharp bound on n for which nL is k-jet ample.Received: 27 December 2002 相似文献