共查询到20条相似文献,搜索用时 15 毫秒
1.
Kazuyoshi Takahashi 《Mathematische Nachrichten》2000,212(1):173-190
We study the k‐very ampleness of the adjoint bundle KS + det E associated to a (k — 1)‐very ample vector bundle E with degree greater than or equal to 4k + 5 on an algebraic surface S. We classify polarized surfaces (S, E) which the k‐very ampleness of KS + det E fails. 相似文献
2.
We classify smooth del Pezzo surfaces whose α-invariant of Tian is bigger than 1. 相似文献
3.
Log Canonical Thresholds of Del Pezzo Surfaces 总被引:1,自引:0,他引:1
Ivan Cheltsov 《Geometric And Functional Analysis》2008,18(4):1118-1144
We study global log canonical thresholds of del Pezzo surfaces.
All varieties are assumed to be defined over .
Received: May 2007 Revision: October 2007 Accepted: April 2008 相似文献
4.
Kazuyoshi Takahashi 《Geometriae Dedicata》1999,77(2):185-201
We investigate ample and spanned rank-2 vector bundles E with k-jet ample determinant on algebraic surfaces S. In paticular, we classify such polarized pairs (S,E) with small second Chern class. The case of c_2(E)=k+1 is a generalization of the result of Ballico and Lanteri. 相似文献
5.
HIRONOBU Ishihara 《Geometriae Dedicata》1997,67(3):309-336
Several classification results for ample vector bundles of rank 2 on Hirzebruch surfaces, and on Del Pezzo surfaces, are obtained. In particular, we classify rank 2 ample vector bundles with c2 less than seven on Hirzebruch surfaces, and with c2 less than four on Del Pezzo surfaces. 相似文献
6.
We study the k-very ampleness of the adjoint bundle K S+det E associated to a k-very ample vector bundle E on an algebraic surface S. We extend the results of Beltrametti and Sommese to the vector bundle case and give the classification of the pairs (S, E) such that the preservation of k-very ampleness fails. 相似文献
7.
We study the arithmetic of certain del Pezzo surfaces of degree2. We produce examples of Brauer-Manin obstruction to the Hasseprinciple, coming from 2- and 4-torsion elements in the Brauergroup. 2000 Mathematics Subject Classification 14G05 (primary),12G05 (secondary). 相似文献
8.
Let X be a non-primary Hopf Surface with Abelian fundamental groupπ_1 (X)(?) Z(?)Z_m, L a line bundle on X, we give a formula for computing the dimension of cohomology H~q(X,Ω~P(L)) and the explicit results for non-primary exceptional Hopf surface. 相似文献
9.
In this paper, we generalise the notion of del Pezzo surfaces to orders on surfaces. We show that these del Pezzo orders have del Pezzo centre if the centre is normal Gorenstein and the order has finite representation type. We proceed to classify these del Pezzo orders. The main result is that if the centre is not or the quadric cone, then these del Pezzo orders can be obtained from del Pezzo orders on . Finally, we classify del Pezzo orders on and the quadric cone. 相似文献
10.
Yoshiaki Fukuma 《Mathematische Nachrichten》2001,224(1):105-121
Let (X, L) be a polarized abelian 3 – fold over the complex number field. In this paper, we classify (X, L) such that |L| has a base point with L3 ≥ 30. 相似文献
11.
We prove a conjecture of J. Alexander concerning the base point freeness and very ampleness of linear systems on general blowings–up of the projective plane, whose standard form has at most 9 multiple points. 相似文献
12.
Giuseppe Pareschi 《Mathematische Annalen》1991,291(1):17-38
Work performed during the author's stay at UCLA, partially supported by Dottorato di Ricerca funds of the Universities of Genova, Milano, Pavia and Torino (1988–1989) and a C.N.R. scholarship (1989–1990) 相似文献
13.
14.
《Chaos, solitons, and fractals》2002,13(6):1371-1373
It is pointed out that the hierarchy of fractal dimensions characterizing transfinite heterotic string space-times bears a striking resemblance to the sequence of the number of lines lying on Del Pezzo surfaces. 相似文献
15.
Alberto Dolcetti 《Annali dell'Universita di Ferrara》2001,47(1):231-241
In this note we classify subcanonical, Gorenstein and complete intersection smooth connected curves lying on del Pezzo surfaces,
by showing their classes in Picard groups of the surfaces.
To Mario Fiorentini 相似文献
Sunto In questa nota si classificano le curve liscie connesse, che sono sottocanoniche, Gorenstein o intersezioni complete, tracciate sulle superfici di del Pezzo, esibendone le classi nei gruppi di Picard delle superfici stesse.
To Mario Fiorentini 相似文献
16.
Sai-Kee Yeung 《Compositio Mathematica》2000,123(2):209-223
Let L be an ample line bundle on a Kähler manifolds of nonpositive sectional curvature with K as the canonical line bundle. We give an estimate of m such that K+mL is very ample in terms of the injectivity radius. This implies that m can be chosen arbitrarily small once we go deep enough into a tower of covering of the manifold. The same argument gives an effective Kodaira Embedding Theorem for compact Kähler manifolds in terms of sectional curvature and the injectivity radius. In case of locally Hermitian symmetric space of noncompact type or if the sectional curvature is strictly negative, we prove that K itself is very ample on a large covering of the manifold. 相似文献
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19.
LetK be a number field. Denote byV
3 a split Del Pezzo surface of degree six overK and by ω its canonical divisor. Denote byW
3 the open complement of the exceptional lines inV
3. LetN
W
s(−ω, X) be the number ofK-rational points onW
3 whose anticanonical heightH
−ω is bounded byX. Manin has conjectured that asymptoticallyN
W
3(−ω, X) tends tocX(logX)3, wherec is a constant depending only on the number field and on the normalization of the height. Our goal is to prove the following
theorem: For each number fieldK there exists a constantc
K such thatN
W
3(−ω, X)≤cKX(logX)3+2r
, wherer is the rank of the group of units ofO
K. The constantc
K is far from being optimal. However, ifK is a purely imaginary quadratic field, this proves an upper bound with a correct power of logX. The proof of Manin's conjecture for arbitrary number fields and a precise treatment of the constants would require a more
sophisticated setting, like the one used by [Peyre] to prove Manin's conjecture and to compute the correct asymptotic constant
(in some normalization) in the caseK=ℚ. Up to now the best result for arbitraryK goes back, as far as we know, to [Manin-Tschinkel], who gives an upper boundN
W
3(−ω,X)≤cXl+ε.
The author would like to express his gratitude to Daniel Coray and Per Salberger for their generous and indispensable support. 相似文献