502 research outputs found
The Aluffi algebra of an ideal
No full textNasrollah Nejad, Abbas; Simis, Aron. The Aluffi algebra of an ideal. 2010. Tese (Doutorado). Programa de Pós-Graduação em Matemática, Universidade Federal de Pernambuco, Recife, 2010.Conselho Nacional de Desenvolvimento Científico e Tecnológic
Commutative Algebra/ Aron Simis.
No full textIn English.This unique book on commutative algebra is divided into two parts in order to facilitate its use in several types of courses. The first introductory part covers the basic theory, connections with algebraic geometry, computational aspects, and extensions to module theory. The more advanced second part covers material such as associated primes and primary decomposition, local rings, M-sequences and Cohen-Macaulay modules, and homological methods.Frontmatter -- Thanks -- Foreword -- Contents -- 1. Basic introductory theory -- 2. Main tools -- 3. Overview of module theory -- 4. Derivations, differentials and Jacobian ideals -- 5. Basic advanced theory -- 6. Homological methods -- 7. Graded structures -- Bibliography -- Index1 online resource (XVI, 340 p.)
Sylvester forms and Rees algebras
No full textThis work is about the Rees algebra of a nite colength almost complete intersection ideal
generated by forms of the same degree in a polynomial ring over a eld. We deal with two
situations which are quite apart from each other: in the rst the forms are monomials in an
unrestricted number of variables, while the second is for general binary forms. The essential
goal in both cases is to obtain the depth of the Rees algebra. It is known that for such ideals the
latter is rarely Cohen{Macaulay (i.e., of maximal depth). Thus, the question remains as to how
far one is from the Cohen{Macaulay case. In the case of monomials one proves under certain
restriction a conjecture of Vasconcelos to the e ect that the Rees algebra is almost Cohen{
Macaulay. At the other end of the spectrum, one proposes a proof of a conjecture of Simis
on general binary forms, based on work of Huckaba{Marley and on a theorem concerning the
Ratli {Rush ltration. Still within this frame, one states a couple of stronger conjectures that
imply Simis conjecture, along with some solid evidence.Este trabalho versa sobre a algebra de Rees de um ideal quase intersec cão completa, de cocomprimento
nito, gerado por formas de mesmo grau em um anel de polinômios sobre um
corpo. Considera-se duas situa c~oes inteiramente diversas: na primeira, as formas s~ao mon^omios
em um n umero qualquer de vari aveis, enquanto na segunda, s~ao formas bin arias gerais. O
objetivo essencial em ambos os casos e obter a profundidade da algebra de Rees. E conhecido
que tal algebra e raramente Cohen{Macaulay (isto e, de profundidade m axima). Assim, a quest~ao
que permanece e qua o distante são do caso Cohen{Macaulay. No caso de monômios prova-se,
mediante certa restri cão, uma conjectura de Vasconcelos no sentido de que a algébra de Rees e
quase Cohen {Macaulay. No outro caso extremo, estabelece-se uma prova de uma conjectura de
Simis sobre formas bin arias gerais, baseada no trabalho de Huckaba{Marley e em um teorema
sobre a ltera cão de Ratli {Rush. Al em disso, apresenta-se um par de conjecturas mais fortes
que implicam a conjectura de Simis, juntamente com uma evidência s olida
Transformações de Cremona definidas por monômios
No full textNesta tese abordamos as seguintes quest~oes: (a) Classificac~ao das aplicac~oes de Cremona
monomial de grau 2 em qualquer numero de variaveis; (b) A estrutura da aplicac~ao
inversa de uma aplicac~ao de Cremona monomial de grau 2; e (c) O papel das bases de Hilbert
em aplicac~oes de Cremona monomial de grau arbitrario. Introduzimos uma forma normal
de uma aplicac~ao de Cremona monomial de grau 2 calcada na estrutura de um grafo cujas
arestas correspondem aos mon^omios que definem a aplicac~ao. Obtemos o formato explicito
da aplicac~ao inversa, bem como os invariantes numericos associados, em termos da natureza
do grafo correspondente. Os resultados s~ao fortemente calcados na vers~ao combinatoria de
birracionalidade para aplicac~oes racionais definidas por mon^omios introduzida por A. Simis
e R. Villarreal. Como aplicac~ao, respondemos afirmativamente a quest~oes propostas por F.
Russo e R. VillarrealUniversidade Federal Rural de Pernambuc
Aron Albahari's reaction to the article in NIN: "Far from the historical truth - Jerusalem has not been the Jewish capital for three thousand years..."
No full textTekst autora Arona Albaharija, koji je bio (neobjavljena) reakcija na prilog objavljen u časopisu NIN, broj 3324, od 11. septembra 2014., u rubrici "U fokusu / Reagovanja", u kome je gost rubrike bio ambasadora u penziji i član Foruma za međunarodne odnose g. Dušan Simeonović. Gospodin Simeonović u tekstu koji naslovljava "Daleko od istorijske istine - Jerusalim nije jevrejska prestonica tri hiljade godina...", daje svoje komentare na ranije objavljeni intervju u ovom listu, sa izraelskim i palestinskim ambasadorima u Beogradu ("Osuđeni jedni na druge", NIN, 4. septembar 2014.).The text of the author Aron Albahari, which was an (unpublished) reaction to an article published in the magazine NIN, number 3324, dated September 11, 2014, in the column "In focus / Reactions", in which the guest of the column was a retired ambassador and member of the Forum for international relations Mr Dušan Simeonović. Mr. Simeonović, in an article titled "Far from the historical truth - Jerusalem has not been the Jewish capital for three thousand years...", gives his comments on an interview previously published in this newspaper, with the Israeli and Palestinian ambassadors in Belgrade ("Condemned to each other", NIN, September 4, 2014)
Cremona transformations and some related algebras
No full textAbstractOne proves a general characteristic-free criterion for a rational map between projective varieties to be birational in terms of ideal-theoretic and modulo-theoretic conditions. This criterion is more inclusive than that of [F. Russo, A. Simis, Compositio Math. 126 (2001) 335–358] and, moreover, differs from previous criteria in its nature in that the syzygies of the base ideal of the map are not directly involved in its formulation. However, a great deal of the consequences are phrased by means of those very syzygies avoided in the formulation of the criterion! In any case, the criterion is stated in effective terms so it yields an efficient computable test of birationality. One also introduces a so-called linear obstruction principle for base ideals of linear type, thus raising a basic question concerning the structure of a certain related “bilinear” algebra
Image-Based Video Search Engine: Feature Extraction
No full textOne of the main problems with Instance-Level Image Retrieval in video data is that for query videos with multiple objects of the same instance, extracting features from keyframes of this query video is time consuming. This thesis aims to solve this problem by implementing a Convolutional Neural Network based approach, which significantly reduces the extraction time and increases the accuracy. After analysing multiple methods, Second-Order Loss and Attention for image Retrieval (SOLAR) was found to be the most promising method. SOLAR will be tested based on three performance metrics: the mean average precision, the recall and the extraction time per image. The performance will be evaluated based on a selection of videos and images from a dataset provided by Dr. Andrea Nanetti from the Engineering Historical Memory project. For this dataset SOLAR achieved a mean average precision of 83 %, a recall of 85 % and an extraction time of 0.73 seconds per image. To conclude, SOLAR is specialised in detecting and describing landmarks due to its pre-trained model, but for a more general case the backbone model should be trained differently which will increase the accuracy. Future work could also include speed improvement by looking at object detection methods.ttps://github.com/aron-hoogeveen/ibvse Link to the codebase (GitHub)Bachelor Graduation ProjectElectrical Engineerin
Symmetric algebras of modules arising from a fixed submatrix of a generic matrix
No full textAbstractWe analyze symmetric algebras which arise from rather ‘bad’ ideals and modules. For example, the ideals are mixed, and every value ≠ 0 occurs as the projective dimension of one of the modules. We are interested in the Cohen-Macaulay property, the canonical module, normality, and the divisor class group. The symmetric algebras under consideration can be defined as residue class rings modulo determinantal ideals covered by the theory of Hochster-Eagon. Part of the results can be regarded as an extension of work of Andrade and Simis
Raymond Aron: ‘La lutte de classes’
No full textPublished in 1964, the result of one of Aron’s four cycles of university lectures dedicated to ‘industrial society’ between 1955 and 1958, La lutte de classes is – as the author himself admitted – one of his best works from a scientific point of view. In the book, the concept of ‘class struggle’, used by Marxists as the main interpretative key of the economic and social transformations generated by industrialism, undergoes a radical critique. According to Aron, it was a political, ideological and metaphysical formula, which was not very useful from the point of view of sociological research. In order to understand the structure and the dynamics of industrial societies, it is instead more useful to reflect on the concepts of ruling class or ruling minority and the way how, within such societies, power is distributed, as well as how the relationships between social groups are structured. What Aron offers in this book is therefore an original re-elaboration of the theory of the élites
Raymond Aron et l'horreur des chiffres
No full textAlain Guerreau. Raymond Aron and the Fear of Figures.
Despite several recent publications, studies on the foundations of historical research in France are still dominated by the works of Raymond Aron. The author examines Raymond Aron's thinking on the role of statistics in historical research, the underlying premises involved in Aron's analysis, its strengths and weaknesses..Alain Guerreau. Raymond Aron et l'horreur des chiffres.
La réflexion sur les fondements de l'activité historienne reste dominée en France, malgré quelques ouvrages récents, par les travaux de Raymond Aron. On analyse la manière dont R. Aron a compris et évalué
l'aspect statistique des recherches historiques, et l'on montre les présupposés qui ont conditionné cette réflexion aronienne et en marquent la faiblesse.Guerreau Alain. Raymond Aron et l'horreur des chiffres. In: Histoire & Mesure, 1986 volume 1 - n°1. Varia. pp. 51-73
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