共查询到20条相似文献,搜索用时 31 毫秒
1.
We study the generic linearly normal special scroll of genus g in P N . Moreover, we give a complete classification of the linearly normal scrolls in P 3 of genus 2 and 3. 相似文献
2.
Gert Monstad Hana 《Mathematische Nachrichten》2006,279(3):242-254
We study Cossec's ? ‐function, which is defined for divisors with positive self‐intersection on an Enriques surface. In this paper we study the existence of pairs (C 2, ? (C )) with C an irreducible curve. The ? ‐function gives in a natural way scrolls containing Enriques surfaces. We compute scroll types to some of these scrolls. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
3.
The aim of this paper is to obtain a classification of scrolls of genus 0 and 1, which are defined by a one-dimensional family
of lines meeting a certain set of linear spaces in p
n
. These ruled surfaces will be called incidence scrolls and such a set will be the base of the incidence scroll. Unless otherwise
stated, we assume that the base spaces are in general position.
Received: 1 December 2000 相似文献
4.
Shigeki Matsuda 《Compositio Mathematica》2002,134(1):1-34
Let k be a field and X = Spec (k[t,t
-1
]). Katz proved that a differential equations with coefficients in k((t
-1
)) is uniquely extended to a special algebraic differential equation on X when k is of characteristic 0. He also proved that a finite extension of k((t
-1
)) is uniquely extended to a special covering of X when k is of any characteristic. These theorems are called canonical extension or Katz correspondence. We shall prove a p-adic analogue of canonical extension for quasi-unipotent overconvergent isocrystals. As a consequence, we can show that the local index of a quasi-unipotent overconvergent is equal to its Swan conductor. 相似文献
5.
V. V. Makeev 《Journal of Mathematical Sciences》1990,51(5):2544-2546
The problem of dividing a unit mass that is continuously distributed inR
n into various ratios by a pencil ofn+1 solid angles is connected with the question of the possibility of homotopies between certain coverings of the sphereS
n–1. We prove that it is possible to inscribe a simplex homothetic to a given simplex in any convex solid region with a smooth boundary. In all the proofs we use the concept of the degree of special mappings onto a canonical simplex and its boundary. One figure.Translated from Ukrainskií Geometricheskií Sbornik, No. 30, 1987, pp. 62–66. 相似文献
6.
Let be a scroll over a smooth curve C and let denote the hyperplane bundle. The special geometry of X implies that certain sheaves related to the principal part bundles of are locally free. The inflectional loci of X can be expressed in terms of these sheaves, leading to explicit formulas for the cohomology classes of the loci. The formulas
imply that the only uninflected scrolls are the balanced rational normal scrolls.
相似文献
7.
E. Ballico 《Israel Journal of Mathematics》2000,119(1):143-155
LetY be a Gorenstein trigonal curve withg:=pa(Y)≥0. Here we study the theory of special linear systems onY, extending the classical case of a smoothY given by Maroni in 1946. As in the classical case, to study it we use the minimal degree surface scroll containing the canonical
model ofY. The answer is different if the degree 3 pencil onY is associated to a line bundle or not. We also give the easier case of special linear series on hyperelliptic curves. The
unique hyperelliptic curve of genusg which is not Gorenstein has no special spanned line bundle. 相似文献
8.
We use methods of the general theory of congruence and *congruence for complex matrices – regularization and cosquares – to determine a unitary congruence canonical form (respectively, a unitary *congruence canonical form) for complex matrices A such that āA (respectively, A 2) is normal. As special cases of our canonical forms, we obtain – in a coherent and systematic way – known canonical forms for conjugate normal, congruence normal, coninvolutory, involutory, projection, λ-projection, and unitary matrices. But we also obtain canonical forms for matrices whose squares are Hermitian or normal, and other cases that do not seem to have been investigated previously. We show that the classification problems under (a) unitary *congruence when A 3 is normal, and (b) unitary congruence when AāA is normal, are both unitarily wild, so these classification problems are hopeless. 相似文献
9.
We study the projective normality of a linearly normal special scroll R of degree d and speciality i over a smooth curve X of genus g. We relate it with the Clifford index of the base curve X. If d ≥ 4g ? 2i ? Cliff(X) + 1, i ≥ 3 and R is smooth, we prove that the projective normality of the scroll is equivalent to the projective normality of its directrix curve of minimum degree. 相似文献
10.
A topological graph is a graph drawn in the plane so that
its vertices are represented by points, and its edges are
represented by Jordan curves connecting the corresponding points,
with the property that any two curves have at most one point in common.
We define two canonical classes of topological complete
graphs, and prove that every topological complete graph with
n vertices has a canonical subgraph of size at least clog1/8
n,
which belongs to one of these classes. We also show
that every complete topological graph with n
vertices has a non-crossing subgraph isomorphic to any fixed
tree with at most clog1/6
n vertices. 相似文献
11.
Alzati A. Bertolini M. Besana G. 《Abhandlungen aus dem Mathematischen Seminar der Universit?t Hamburg》2004,74(1):57-75
Smooth, complex, ruled surfaces embedded in ℙ5 as linearly normal scrolls, such that they are contained in a quadric cone, are considered. Rational scrolls and some elliptic
scrolls are shown to be the only ones contained in cones of rank 5. Results on scrolls contained in cones of lower ranks are
also obtained. 相似文献
12.
Stanislav Smirnov 《Acta Mathematica》2010,205(1):189-197
We introduce canonical antisymmetric quasiconformal maps, which minimize the quasiconformality constant among maps sending
the unit circle to a given quasicircle. As an application we prove Astala’s conjecture that the Hausdorff dimension of a k-quasicircle is at most 1+k
2. 相似文献
13.
A general notion of canonical correlation is developed that extends the classical multivariate concept to include function-valued random elements X and Y. The approach is based on the polar representation of a particular linear operator defined on reproducing kernel Hilbert spaces corresponding to the random functions X and Y. In this context, canonical correlations and variables are limits of finite-dimensional subproblems thereby providing a seamless transition between Hotelling’s original development and infinite-dimensional settings. Several infinite-dimensional treatments of canonical correlations that have been proposed for specific problems are shown to be special cases of this general formulation. We also examine our notion of canonical correlation from a large sample perspective and show that the asymptotic behavior of estimators can be tied to that of estimators from standard, finite-dimensional, multivariate analysis. 相似文献
14.
Summary In this article we exhibit certain projective degenerations of smoothK3 surfaces of degree 2g–2 in
g
(whose Picard group is generated by the hyperplane class), to a union of two rational normal scrolls, and also to a union of planes. As a consequence we prove that the general hyperplane section of suchK3 surfaces has a corank one Gaussian map, ifg=11 org13. We also prove that the general such hyperplane section lies on a uniqueK3 surface, up to projectivities. Finally we present a new approach to the classification of prime Fano threefolds of index one, which does not rely on the existence of a line.Oblatum 1-II-1993 & 24-V-1993Research supported in part by NSF grant DMS-9104058 相似文献
15.
Yvette Kosmann-Schwarzbach 《Bulletin of the Brazilian Mathematical Society》2011,42(4):625-649
We study Nijenhuis structures on Courant algebroids in terms of the canonical Poisson bracket on their symplectic realizations.
We prove that the Nijenhuis torsion of a skew-symmetric endomorphism N of a Courant algebroid is skewsymmetric if N
2 is proportional to the identity, and only in this case when the Courant algebroid is irreducible. We derive a necessary and
sufficient condition for a skewsymmetric endomorphism to give rise to a deformed Courant structure. In the case of the double
of a Lie bialgebroid (A, A*), given an endomorphism N of A that defines a skew-symmetric endomorphism N of the double of A, we prove that the torsion ofN is the sum of the torsion of N and that of the transpose of N. 相似文献
16.
We obtain necessary and sufficient conditions for the integrability in quadratures of geodesic flows on homogeneous spaces M with invariant and central metrics. The proposed integration algorithm consists in using a special canonical transformation in the space T
*
M based on constructing the canonical coordinates on the orbits of the coadjoint representation and on the simplectic sheets of the Poisson algebra of invariant functions. This algorithm is applicable to integrating geodesic flows on homogeneous spaces of a wild Lie group. 相似文献
17.
Sérgio Alvarez Lev Birbrair João Carlos Ferreira Costa Alexandre Fernandes 《Central European Journal of Mathematics》2010,8(2):338-345
We study the topological K-equivalence of function-germs (ℝ
n
, 0) → (ℝ, 0). We present some special classes of piece-wise linear functions and prove that they are normal forms for equivalence
classes with respect to topological K-equivalence for definable functions-germs. For the case n = 2 we present polynomial models for analytic function-germs. 相似文献
18.
19.
We use a generalization of Wiener's 1/f theorem to prove that for a Gabor frame with the generator in the Wiener amalgam space W(L∞,?1)(Rd), the corresponding frame operator is invertible on this space. Therefore, for such a Gabor frame, the canonical dual belongs also to W(L∞,?1)(Rd). 相似文献
20.
We show that up to a translation each automorphism of the derived category D b X of coherent sheaves on a weighted projective line X, equiv-alently of the derived category D b A of finite dimensional modules over a derived canonical algebra A, is composed of tubular mutations and automorphisms of X. In the case of genus one this implies that the automorphism group is a semi-direct product of the braid group on three strands by a finite group. Moreover we prove that most automorphisms lift from the Grothendieck group to the derived category. 相似文献