“…Take k = 2, a > 0 and d > 0. It is sufficient to do the following cases (d, a): (1, 1), (2, 1), (1,2). The first one is not defective, because h 0 (I Y (1,1) (2)) = 3 and hence h 1 (I Y (1,1) (2)) = 0.…”
Section: Preliminariesmentioning
confidence: 99%
“…Since a general rational curve of degree d has maximal rank, it is sufficient to check the following pairs (d, a): (1, 4), (2,3), (2,4), (3,2), (3,3), (4, 1), (4, 2), (5, 1), (6,1). For the case (d, a) = (1, 4), see [4,Corollary 2].…”
“…Hence h i (Q, I (U ∩Q)∪S ′ (k)) = 0, i = 0, 1. By the differential Horace lemma for double points ( [1], [11,Lemma 5], [2] in characteristic = 2) to prove that h 1 (I W (k)) = 0 it is sufficient to prove …”
Section: Preliminariesmentioning
confidence: 99%
“…Hence to prove Theorem 1 for the triple (d, a, k) it is sufficient to prove that h 1 (I W (k)) = 0, where W is the union of U and f general 2-points. We have [2] in characteristic = 2) to prove that h 1 (I W (k)) = 0 it is sufficient to prove that…”
Abstract:We study the Hilbert function of general unions in P r , r = 3, 4, of a prescribed number of double points and a rational curve with a prescribed degree.
“…Take k = 2, a > 0 and d > 0. It is sufficient to do the following cases (d, a): (1, 1), (2, 1), (1,2). The first one is not defective, because h 0 (I Y (1,1) (2)) = 3 and hence h 1 (I Y (1,1) (2)) = 0.…”
Section: Preliminariesmentioning
confidence: 99%
“…Since a general rational curve of degree d has maximal rank, it is sufficient to check the following pairs (d, a): (1, 4), (2,3), (2,4), (3,2), (3,3), (4, 1), (4, 2), (5, 1), (6,1). For the case (d, a) = (1, 4), see [4,Corollary 2].…”
“…Hence h i (Q, I (U ∩Q)∪S ′ (k)) = 0, i = 0, 1. By the differential Horace lemma for double points ( [1], [11,Lemma 5], [2] in characteristic = 2) to prove that h 1 (I W (k)) = 0 it is sufficient to prove …”
Section: Preliminariesmentioning
confidence: 99%
“…Hence to prove Theorem 1 for the triple (d, a, k) it is sufficient to prove that h 1 (I W (k)) = 0, where W is the union of U and f general 2-points. We have [2] in characteristic = 2) to prove that h 1 (I W (k)) = 0 it is sufficient to prove that…”
Abstract:We study the Hilbert function of general unions in P r , r = 3, 4, of a prescribed number of double points and a rational curve with a prescribed degree.
In this survey, we report on progress concerning families of projective curves with fixed number and fixed (topological or analytic) types of singularities. We are, in particular, interested in numerical, universal and asymptotically proper sufficient conditions to guarantee the nonemptyness, T-smoothness and irreducibility of the variety of all projective curves with prescribed singularities in a fixed linear system. We also discuss the analogous problem for hypersurfaces of arbitrary dimension with isolated singularities, and we close with a section on open problems and conjectures.
These notes are a record of lectures given in the Workshop on Connections Between Algebra and Geometry at the University of Regina, May 29-June 1, 2012. The lectures were meant as an introduction to current research problems related to fat points for an audience that was not expected to have much background in commutative algebra or algebraic geometry (although sections 8 and 9 of these notes demand somewhat more background than earlier sections).
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