Search results for "Isomorphism"
showing 10 items of 62 documents
Rasiowa–Sikorski Sets and Forcing
2018
The paper is concerned with the problem of building models for first-order languages from the perspective of the classic paper of Rasiowa and Sikorski (1950). The central idea, due to Rasiowa and Sikorski and developed in this paper, is constructing first-order models from individual variables. The notion of a Rasiowa–Sikorski set of formulas of an arbitrary language L is introduced. Investigations are confined to countable languages. Each Rasiowa–Sikorski set defines a countable model for L. Conversely, each countable model for L is determined, up to isomorphism, by some Rasiowa–Sikorski set. Consequences of these facts are investigated.
El «nacionalismo metodológico» como obstáculo en la investigación sociológica sobre migraciones internacionales
2007
La globalizacion ha evidenciado la necesidad de cuestionar el ‘nacionalismo metodologico’ como presupuesto fundamental de la primera modernidad. Este cuestionamiento rompe la asuncion de que los contornos de la sociedad coinciden con los del estado- nacion, y supone un desafio epistemologico para la sociologia, que desde su nacimiento adopto un esquema de clasificacion del espacio social que podria denominarse isomorfismo estado-sociedad. En este articulo realizamos una reflexion sobre los desafios epistemologicos y metodologicos que las migraciones internacionales suponen para la sociologia y las practicas de investigacion social mayoritarias, que generalmente arrastran inercias y presupue…
Analogy Construction and Success in Mathematics and Science Problem-solving: a Study with Secondary Students // Construcción de analogías y éxito en …
2012
We conducted an empirical study to analyse the association between students’ perception of surface and structural analogies between problems, and their algebraic success. Different surface and structural relationships between one ‘source’ problem and ‘target’ problems were considered. We also considered high (daily life) and low (scientific) familiarity contexts. Algebraic success was measured by the equations selected to solve each problem. Similarities and differences between problems were explicitly asked to students. Results showed a significant correlation between detecting the correct structural relation between problems and selecting the correct equations to solve them. Low familiari…
Vassiliev invariants for braids on surfaces
2000
We show that Vassiliev invariants separate braids on a closed oriented surface, and we exhibit an universal Vassiliev invariant for these braids in terms of chord diagrams labeled by elements of the fundamental group of the considered surface.
Problems and Techniques
2017
When biological networks are considered, the extraction of interesting knowledge often involves subgraphs isomorphism check that is known to be NP-complete. For this reason, many approaches try to simplify the problem under consideration by considering structures simpler than graphs, such as trees or paths. Furthermore, the number of existing approximate techniques is notably greater than the number of exact methods. In this chapter, we provide an overview of three important problems defined on biological networks: network alignment, network clustering, and motifs extraction from biological networks. For each of these problems, we also describe some of the most important techniques proposed…
Approximate Matching over Biological RDF Graphs
2012
In the last few years, the amount of biological interaction data discovered and stored in public databases (e.g., KEGG [2]) considerably increased. To this aim, RDF is a powerful representation for interactions (or pathways), since they can be modeled as directed graphs, often referred to as biological networks, where nodes represent cellular components and the (labeled or unlabeled) edges correspond to interactions among components. Often for a given organism some components are known to be linked by well studied interactions. Such groups of components are called modules and they can be represented by sub-graphs in the corresponding biological network model. At today, one of the most impor…
Are images in the Tractatus isomorphic to facts?
2010
The notion of image (Bild) is a fundamental one in the Tractatus. This notion is immediately introduced in the text after the brief ontological section, because it serves to give an account in logical terms of our relationship with the world. The relationship between fact and image is generally considered a relationship governed by a form of isomorphism. Here I want to maintain that it is not a matter isomorphism, but instead of homomorphism.
Hamel-isomorphic images of the unit ball
2010
In this article we consider linear isomorphisms over the field of rational numbers between the linear spaces ℝ2 and ℝ. We prove that if f is such an isomorphism, then the image by f of the unit disk is a strictly nonmeasurable subset of the real line, which has different properties than classical non-measurable subsets of reals. We shall also consider the question whether all images of bounded measurable subsets of the plane via a such mapping are non-measurable (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
Unit Operations in Approximation Spaces
2010
Unit operations are some special functions on sets. The concept of the unit operation originates from researches of U. Wybraniec-Skardowska. The paper is concerned with the general properties of such functions. The isomorphism between binary relations and unit operations is proved. Algebraic structures of families of unit operations corresponding to certain classes of binary relations are considered. Unit operations are useful in Pawlak's Rough Set Theory. It is shown that unit operations are upper approximations in approximation space. We prove, that in the approximation space (U, R) generated by a reflexive relation R the corresponding unit operation is the least definable approximation i…
Automorphisms and abstract commensurators of 2-dimensional Artin groups
2004
In this paper we consider the class of 2-dimensional Artin groups with connected, large type, triangle-free defining graphs (type CLTTF). We classify these groups up to isomorphism, and describe a generating set for the automorphism group of each such Artin group. In the case where the defining graph has no separating edge or vertex we show that the Artin group is not abstractly commensurable to any other CLTTF Artin group. If, moreover, the defining graph satisfies a further `vertex rigidity' condition, then the abstract commensurator group of the Artin group is isomorphic to its automorphism group and generated by inner automorphisms, graph automorphisms (induced from automorphisms of the…