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Cohen-Macaulay Property of pinched Veronese Rings and Canonical Modules of Veronese  Modules
KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Mathematics (Div.). (Algebraic Geometry)
(English)Manuscript (preprint) (Other academic)
##### Abstract [en]

In this paper, we study the Betti numbers of pinched Veronese rings, by means of the reduced homology of the squarefree divisor complex. In particular, we study the Cohen-Macaulay property of these rings. Moreover, in the last section we compute the canonical modules of the Veronese modules.

##### Keywords [en]
pinched veronese, cohen-macaulay, canonical module
##### National Category
Algebra and Logic
##### Identifiers
OAI: oai:DiVA.org:kth-158912DiVA, id: diva2:779980
##### Note

QS 2015

Available from: 2015-01-13 Created: 2015-01-13 Last updated: 2015-01-15Bibliographically approved
##### In thesis
1. Bounds on Hilbert Functions and Betti Numbers of Veronese Modules
Open this publication in new window or tab >>Bounds on Hilbert Functions and Betti Numbers of Veronese Modules
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
##### Abstract [en]

The thesis is a collection of four papers dealing with Hilbert functions and Betti numbers.In the first paper, we study the h-vectors of reduced zero-dimensional schemes in $\mathbb{P}^{2}$ . In particular we deal with the problem of findingthe possible h-vectors for the union of two sets of points of given h-vectors. To answer to this problem, we give two kinds of bounds on theh-vectors and we provide an algorithm that calculates many possibleh-vectors.In the second paper, we prove a generalization of Green’s Hyper-plane Restriction Theorem to the case of finitely generated modulesover the polynomial ring, providing an upper bound for the Hilbertfunction of the general linear restriction of a module M in a degree dby the corresponding Hilbert function of a lexicographic module.In the third paper, we study the minimal free resolution of theVeronese modules, $S_{n,d,k}=\oplus_{i\geq 0} S_{k+id}$, where  $S = \mathbb{K}[x_1 , . . . , x_n ]$ by giving a formula for the Betti numbers in terms of the reduced homology of the squarefree divisor complex. We prove that $S_{n,d,k}$ is Cohen-Macaulay if and only if k < d, and that its minimal resolutionis linear when k > d(n − 1) − n. We prove combinatorially that the resolution of $S_{2,d,k}$ is pure. We provide a formula for the Hilbert seriesof the Veronese modules. As an application, we calculate the completeBetti diagrams of the Veronese rings $S_{3,4,0} , S_{3,5,0} and S_{4,3,0}$ .In the fourth paper, we apply the same combinatorial techniques inthe study of the properties of pinched Veronese rings, in particular weshow when this ring is Cohen-Macaulay. We also study the canonicalmodule of the Veronese modules.

##### Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2014. p. vii, 31
##### Series
TRITA-MAT-A ; 2014:16
##### Keywords
Hilbert function, Betti numbers, Veronese modules, Pinched veronese, h-vectors
##### National Category
Algebra and Logic Geometry
Mathematics
##### Identifiers
urn:nbn:se:kth:diva-158913 (URN)978-91-7595-394-6 (ISBN)
##### Public defence
2015-02-04, F3, Lindstedtsvägen 26, KTH, Stockholm, 14:00 (English)
##### Note

QC 20150115

Available from: 2015-01-15 Created: 2015-01-13 Last updated: 2015-01-15Bibliographically approved

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Cite
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