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Resolutions of singularities using blow-ups
Komora, Matúš ; Šťovíček, Jan (advisor) ; Hrbek, Michal (referee)
This bachelor's thesis aims to provide accessible treatment of the blow-up construction for algebraic varieties. The blow-up construction is a fundamen- tal technique in algebraic geometry that allows us to find a variety which has better properties than an original variety but is still equivalent to the original. This process can be used to resolve singularities. In the first two chapters, we begin by providing an introduction to the fundamental principles of alge- braic geometry, including the definitions of algebraic varieties but also basic topological concepts but also some construction such as Segre embedding and product of varieties. In the third chapter, we will introduce the concept of blow-ups and show the computation as on example. 1
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Local properties of modules
Lysoněk, Tomáš ; Hrbek, Michal (advisor) ; Příhoda, Pavel (referee)
This thesis introduces module properties of projectivity and flatness relative to classes of finitely presented modules, these being generalization of projectivity and pure pro- jectivity. Then it gives proof of ascent and descent of these properties through non- commutative ring homomorphisms with certain properties, most importantly reflection of pure epimorphisms. For relative case ascent and descent through flat ring homomor- phisms, which reflect pure epimorphisms, is given. Finally, these results are applied in the setting of homomorphisms arising as central extensions of pure and faithfully flat central ring homomorphisms. 1
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Sudé triangulace a Abelovy grupy
Hrbek, Michal ; Drápal, Aleš (advisor) ; Kepka, Tomáš (referee)
Title: Even triangulations and Abelian groups Author: Michal Hrbek Department: Department of Algebra Supervisor: prof. RNDr. Aleš Drápal CSc., DSc. Abstract: This thesis takes interest in spherical Eulerian triangulations and the algebraic structure defined on its vertices corresponding with the latin bitrade equivalent to the triangulation. First, we introduce needed results about the properties of the triangulations and their embeddings into Abelian groups. Then we get concerned with a particular kind of almost 6-homogenous triangulations. The text presents several examples, then the groups of the simplest sequence of triangulations are explicitly described. In order to investigate more complicated cases, we introduce a recursive formula for defining relations of the groups and we show an example of its usage with modular arithmetic. The thesis is completed by discussing computed data. Keywords: latin bitrade, eulerian triangulation, Abelian group 1
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Tilting theory of commutative rings
Hrbek, Michal ; Trlifaj, Jan (advisor) ; Herbera Espinal, Dolors (referee) ; Šaroch, Jan (referee)
The thesis compiles my contributions to the tilting theory, mainly in the set- ting of a module category over a commutative ring. We give a classification of tilting classes over an arbitrary commutative ring in terms of data of geometrical flavor - certain filtrations of the Zariski spectrum. This extends and connects the results known previously for the noetherian case, and for Prüfer domains. Also, we show how the classes can be expressed using the local and Čech homology the- ory. For 1-tilting classes, we explicitly construct the associated tilting modules, generalizing constructions of Fuchs and Salce. Furthermore, over any commuta- tive ring we classify the silting classes and modules. Amongst other results, we exhibit new examples of cotilting classes, which are not dual to any tilting classes - a phenomenon specific to non-noetherian rings. 1
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Moduly s minimální množinou generátorů
Hrbek, Michal
Title: Modules with a minimal generating set Author: Michal Hrbek Department: Department of Algebra Supervisor: Mgr. Pavel Růžička, Ph.D., Department of Algebra Abstract: By a minimal generating set of a module we mean a subset which generates the module but any of its proper subsets does not. If the module is not finitely generated, an existence of a minimal generating set is not guaranteed. We say that a module is weakly based if it has a minimal generating set. In the presented thesis, we provide a characterization of weakly based modules over Dedekind domains. As an application of this, we show that the class of weakly based modules is not closed under extensions and the complement of this class is not closed under finite direct sums. Also, we show an example of an abelian group which is weakly based if and only if CH holds. Then we treat rings such that all modules are weakly based. We prove that a Baer regular ring has this property if and only if it is semisimple, and we show that any ℵ0-noetherian commutative semiartinian ring has this property. Final part of the text concerns the problem of Nashier and Nichols - does any generating set of any module over a perfect ring contain a minimal generating set? Keywords: module, minimal generating set, weak basis 1
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Basics on persistent homology
Novák, Jakub ; Šťovíček, Jan (advisor) ; Hrbek, Michal (referee)
Abstract:In this work, the reader is introduced to the theory of persistent ho- mology and its applications. In the first chapter we will show the basics of sim- plicial and singular homology and we will prove the basic relations, especially the independence of simplicial homological groups on the chosen △-complex and isomorphism between homological groups of homotopic spaces. In the second chapter, we explain the motivation behind persistent homology, describe its al- gebraic structure and how it can be visually represented. We describe and prove the corectness of the algorithm for its calculation. We then illustrate the theory on an example. 1
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Tilting theory of commutative rings
Hrbek, Michal ; Trlifaj, Jan (advisor) ; Herbera Espinal, Dolors (referee) ; Šaroch, Jan (referee)
The thesis compiles my contributions to the tilting theory, mainly in the set- ting of a module category over a commutative ring. We give a classification of tilting classes over an arbitrary commutative ring in terms of data of geometrical flavor - certain filtrations of the Zariski spectrum. This extends and connects the results known previously for the noetherian case, and for Prüfer domains. Also, we show how the classes can be expressed using the local and Čech homology the- ory. For 1-tilting classes, we explicitly construct the associated tilting modules, generalizing constructions of Fuchs and Salce. Furthermore, over any commuta- tive ring we classify the silting classes and modules. Amongst other results, we exhibit new examples of cotilting classes, which are not dual to any tilting classes - a phenomenon specific to non-noetherian rings. 1
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Moduly s minimální množinou generátorů
Hrbek, Michal
Title: Modules with a minimal generating set Author: Michal Hrbek Department: Department of Algebra Supervisor: Mgr. Pavel Růžička, Ph.D., Department of Algebra Abstract: By a minimal generating set of a module we mean a subset which generates the module but any of its proper subsets does not. If the module is not finitely generated, an existence of a minimal generating set is not guaranteed. We say that a module is weakly based if it has a minimal generating set. In the presented thesis, we provide a characterization of weakly based modules over Dedekind domains. As an application of this, we show that the class of weakly based modules is not closed under extensions and the complement of this class is not closed under finite direct sums. Also, we show an example of an abelian group which is weakly based if and only if CH holds. Then we treat rings such that all modules are weakly based. We prove that a Baer regular ring has this property if and only if it is semisimple, and we show that any ℵ0-noetherian commutative semiartinian ring has this property. Final part of the text concerns the problem of Nashier and Nichols - does any generating set of any module over a perfect ring contain a minimal generating set? Keywords: module, minimal generating set, weak basis 1
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Moduly s minimální množinou generátorů
Hrbek, Michal ; Růžička, Pavel (advisor) ; Trlifaj, Jan (referee)
Title: Modules with a minimal generating set Author: Michal Hrbek Department: Department of Algebra Supervisor: Mgr. Pavel Růžička, Ph.D., Department of Algebra Abstract: By a minimal generating set of a module we mean a subset which generates the module but any of its proper subsets does not. If the module is not finitely generated, an existence of a minimal generating set is not guaranteed. We say that a module is weakly based if it has a minimal generating set. In the presented thesis, we provide a characterization of weakly based modules over Dedekind domains. As an application of this, we show that the class of weakly based modules is not closed under extensions and the complement of this class is not closed under finite direct sums. Also, we show an example of an abelian group which is weakly based if and only if CH holds. Then we treat rings such that all modules are weakly based. We prove that a Baer regular ring has this property if and only if it is semisimple, and we show that any ℵ0-noetherian commutative semiartinian ring has this property. Final part of the text concerns the problem of Nashier and Nichols - does any generating set of any module over a perfect ring contain a minimal generating set? Keywords: module, minimal generating set, weak basis 1
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Sudé triangulace a Abelovy grupy
Hrbek, Michal ; Drápal, Aleš (advisor) ; Kepka, Tomáš (referee)
Title: Even triangulations and Abelian groups Author: Michal Hrbek Department: Department of Algebra Supervisor: prof. RNDr. Aleš Drápal CSc., DSc. Abstract: This thesis takes interest in spherical Eulerian triangulations and the algebraic structure defined on its vertices corresponding with the latin bitrade equivalent to the triangulation. First, we introduce needed results about the properties of the triangulations and their embeddings into Abelian groups. Then we get concerned with a particular kind of almost 6-homogenous triangulations. The text presents several examples, then the groups of the simplest sequence of triangulations are explicitly described. In order to investigate more complicated cases, we introduce a recursive formula for defining relations of the groups and we show an example of its usage with modular arithmetic. The thesis is completed by discussing computed data. Keywords: latin bitrade, eulerian triangulation, Abelian group 1
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