Results 21 to 30 of about 1,787 (109)
General position of points on a rational ruled surface [PDF]
Beiträge zur Algebra und Geometrie / Contributions to Algebra and Geometry, 2017 There are several different definitions for the notion of points in general position in \(\mathbb{P}^2\), some of which, due to the authors, are finalized to very ampleness criteria for rank 2 vector bundles [\textit{A. Alzati} and \textit{A. Tortora}, Rev. Mat. Complut. 28, No. 3, 623--654 (2015; Zbl 1330.14070)].
A. ALZATI, A. Tortora
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Rational curves and ruled orders on surfaces
Journal of Algebra, 2015 We study ruled orders. These arise naturally in the Mori program for orders on projective surfaces and morally speaking are orders on a ruled surface ramified on a bisection and possibly some fibres. We describe fibres of a ruled order and show they are in some sense rational.
Daniel Chan, Kenneth Chan
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Normal projective degenerations of rational and ruled surfaces.
Journal für die reine und angewandte Mathematik (Crelles Journal), 1986 Let \(f: X\to T\) be a projective flat morphism from a normal threefold X to a smooth affine curve T over the field of complex numbers. Suppose that \(X_ t\) is a smooth surface for \(t\neq 0\) and \(X_ 0\) is a normal surface, where \(0\in T\) is a distinguishd point. Then \(X_ 0\) is a called a normal projective degeneration of \(X_ t\).
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Affine rulings of normal rational surfaces
Osaka Journal of Mathematics, 2001 zbMATH Open Web Interface contents unavailable due to conflicting licenses.
Daigle, Daniel, Russell, Peter
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Computing the symmetries of a ruled rational surface
, 2018 We present a method for computing all the symmetries of a rational ruled surface defined by a rational parametrization which works directly in parametric rational form, i.e. without computing or making use of the implicit equation of the surface. The method proceeds by translating the problem into the parameter space, and relies on polynomial system ...
Arribas, Alcázar +2 more
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Intersections numbers on the compact variety of rational ruled surfaces [PDF]
, 2006 We consider the Quot scheme, R_{d}, compactifying the space of degree d maps from the projective line to the Grassmannian of lines. We give an algorithm for computing the degree of R_{d} under a "generalized Plücker embedding", this is a certain Gromov-Witten invariant. The approach is to apply the Atiyah-Bott localization formula for the natural C^{*}-
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Enumerative formulae for ruled cubic surfaces and rational quintic curves
Commentarii Mathematici Helvetici, 1986 For varieties in \({\mathbb{P}}^ 3\), the classical enumerative geometers obtained their results for curves of degree \(\leq 4\) and surfaces of degree \(\leq 2.\) Here the program is continued with new results about ruled cubic surfaces and rational quintic curves.
Vainsencher, Israel, Coray, Daniel F.
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The degree of the variety of rational ruled surfaces and Gromov-Witten invariants [PDF]
Transactions of the American Mathematical Society, 2005 We compute the degree of the variety parametrizing rational ruled surfaces of degree d in the projective space by relating the problem to Gromov-Witten invariants and Quantum cohomology.
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On Donaldson polynomials of rational ruled surfaces
Forum Mathematicum, 1996 Let \(\pi:X= \mathbb{F}_e\to\mathbb{P}^1\) be a rational ruled surface, where \(e\) is a nonnegative integer. Let \(f\) be a fibre of \(\pi\) and \(\sigma\) be a section to \(\pi\) with \(\sigma^2=-e\). Fix an integer \(c\). An ample divisor \((a\sigma+bf)\) is defined to be \(c\)-suitable if \(b/a> (c+e)/2\).
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Centralizers of Hamiltonian Circle Actions on Rational Ruled Surfaces
Memoirs of the American Mathematical SocietyWe compute the homotopy type of the group of equivariant symplectomorphisms of S 2
Chakravarthy, Pranav +1 more
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