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Abelian regular rings
Vejnar, Benjamin ; Žemlička, Jan (advisor) ; Růžička, Pavel (referee)
Na/ev praco: Abelovsky regularni okruhy Autor: Benjamin Vejnar Katedra (listav): Katedra algebry VcdoLici bakalafske prace: Mgr. Jan 2emlicka, Ph.D. E-mail vedouctho: Jan.Zcmlicka&mJJ. cuni.cz Abstrakt: V pfcdloxene praci studujeme aritmeticke a strukturni vlastnosti abelovsky regularnich okruhu, tedy okruhu, jcjichx ka/xly levy i pravy konecne generova.ny ideal jo generovan idempotentnim prvkem, klery Ic/i v centra danoho okruhu. Napfiklad ka/,dy Boohmv okruh je abelovsky regularni. Venujume ye podininkam, ktere uplne diarakterizuji tn'du abelovsky regu- larnieli okruhu, jako napfiklad silna regularita. Vsimame si souvislosti mexi Booleovou algebrou vsch centralnich idempo1,entu daneho okruhu a hlavnimi idealy. Dale popiHUJeme topologit na nmo/ine visecli prvoidealu a avcdoniujeine si, '/e splyva s Lo])ologii ultrafiltrii na Booleove algebre idciiipotontd. Klicova slova: okruhy, idempoteiitni prvky, silne regularni okruhy Title: Abelian regular rings Author: Benjamin Vejnar Department: Department of Algebra Supervisor: Mgr. Jan Zemlieka, Ph.D. Supervisor's e-mail address: Jan.Zc:ttilicka((})'niff.cu'iii.cz Abstract: In the present work we study arithmetic and structural properties of abelian regular' rings. This means rings whose every left and right finitely generated ideal is generated by an idempotent...
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Qudratic field based cryptography
Straka, Milan ; Stanovský, David (advisor) ; Žemlička, Jan (referee)
Imaginary quadratic fields were first suggested as a setting for public-key cryptography by Buchmann and Williams already in 1988 and more cryptographic schemes followed. Although the resulting protocols are currently not as efficient as those based on elliptic curves, they are comparable to schemes based on RSA and, moreover, their security is believed to be independent of other widely-used protocols including RSA, DSA and elliptic curve cryptography. This work gathers present results in the field of quadratic cryptography. It recapitulates the algebraic theory needed to work with the class group of imaginary quadratic fields. Then it investigates algorithms of class group operations, both asymptotically and practically effective. It also analyses feasible cryptographic schemes and attacks upon them. A library implementing described cryptographic schemes is a part of this work.
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Solving systems of equations over commutative rings
Seidl, Jan ; Šťovíček, Jan (advisor) ; Žemlička, Jan (referee)
The object of this work is to offer algorithm how can be solved systems of linear equations Ax=b over principal ideal rings. We prove that for every nonzero matrix over principal ideal rings there exists its Smith form. Using Smith form we transform the system of equations to simple diagonal form and we show how we can obtain the solution of the original system from its diagonal form. Whole procedure we demonstrate by the examples over Z, Zm and Q[x]. Thereafter we show how is possible to implement the algorithm for these rings by using software Mathematica. The work should provide procedure according to which shold not be difficult to modify algorithm to gain solution over another rings. 1
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Algorithm for word morphisms fixed points
Matocha, Vojtěch ; Holub, Štěpán (advisor) ; Žemlička, Jan (referee)
In the present work we study the first polynomial algorithm, which tests if the given word is a fixed point of a nontrivial morphism. This work contains an improved worst-case complexity estimate O(m · n) where n denotes the word length and m denotes the size of the alphabet. In the second part of this work we study the union-find problem, which is the crucial part of the described algorithm, and the Ackermann function, which is closely linked to the union-find complexity. We summarize several common methods and their time complexity proofs. We also present a solution for a special case of the union-find problem which appears in the studied algorithm. The rest of the work focuses on a Java implementation, whose time tests correspond to improved upper bound, and a visualization useful for particular entries.
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Varieties of superalgebras
Lišková, Adéla ; Žemlička, Jan (advisor) ; Barto, Libor (referee)
The goal of the thesis is to introduce the basics of the theory of superalgebras, that is Z2-graded algebras over a field of characteristic different from two, as well as to present necessary basics of universal and multilinear algebra, especially the tensor product and the terms variety of algebra and ideal of identities. We present the definitions of algebra and superalgebra including examples, we then look into the tensor product of superalgebras and its properties, Clifford and Grassmann superalgebras. A part of the thesis is dedicated to the construction of the free nonassociative algebra and the clarification of the relationship between varieties of algebras and ideals of identities including the specification of said relationship for superalgebras. The thesis also deals with varieties of superalgebras. 1
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