Hemeroteca del mes agosto, 2014

JVR: Podría estar dándose una distensión en la relación entre EEUU y Venezuela

Por • 31 ago, 2014 • Category: Nacionales

Se están dando pasos, que por lo general no trasciende en los medios de comunicación, que parecieran presagiar cambios en las relaciones entre los EE.UU. y Venezuela



El precio de la gasolina

Por • 31 ago, 2014 • Category: Nacionales

El jueves celebramos un foro sobre el ajuste del precio de la gasolina, su necesidad y sus efectos, donde participaron expertos de diversas tendencias y actividades, y donde por vez primera el ponente principal, en este caso el ministro de Petróleo y Energía, Rafael Ramírez, estuvo ausente, no obstante que nos habían confirmado su asistencia.



A Note on the Decidability of the Necessity of Axioms

Por • 31 ago, 2014 • Category: Leyes

A typical kind of question in mathematical logic is that for the necessity of a certain axiom: Given a proof of some statement ϕ in some axiomatic system T , one looks for minimal subsystems of T that allow deriving ϕ . In particular, one asks whether, given some system T+ψ , T alone suffices to prove ϕ . We show that this problem is undecidable unless T+¬ψ is decidable.



La gran comilona

Por • 31 ago, 2014 • Category: Nacionales

Cuando el exministro de Cordiplan, Jorge Giordani, habló de que sólo en 2012 se habían evaporado más de 20 mil millones de dólares, otorgados a empresas de maletín, apenas asomó la punta de un iceberg de corrupción que probablemente no tiene antecedentes en el mundo entero



Astrosociology: Interwiews about an infinite universe

Por • 31 ago, 2014 • Category: sociologia

If the universe is infinite now it has always been infinite. This is the opinion of many astronomers today as can be concluded from the following series of interviews, but the opinions differ much more than I had expected. Many astronomers do not have a clear opinion on this matter. Others have a clear opinion, but very different from the majority. Detailed arguments by two experts on general relativity are also included. Observations show that the universe is flat, i.e. the curvature is zero within the small uncertainty of measurements. This implies an infinite universe, though most probably we will never know that for certain. For comparison with the recent interviews, opinions during the past 2300 years since Aristotle about the universe being finite or infinite have been collected from literature, and it appears that the scientists often had quite definite opinions. copyright Anita Publications. All rights reserved.



A New Algebraic Version of Monteiro’s Four-Valued Propositional Calculus

Por • 31 ago, 2014 • Category: Opinion

In the XII Latin American Symposium on Mathematical Logic we presented a work introducing a Hilbert-style propositional calculus called four-valued Monteiro propositional calculus. This calculus, denoted by M4, is introduced in terms of the binary connectives (implication), → (weak implication), ∧ (conjunction) and the unary ones (negation) and ▽ (modal operator). In this paper, it is proved that M4 belongs to the class of standard systems of implicative extensional propositional calculi as defined by Rasiowa (1974). Furthermore, we show that the definitions of four-valued modal algebra and M4 -algebra are equivalent and, in addition, obtain the completeness theorem for M4. We also introduce the notion of modal distributive lattices with implication and show that these algebras are more convenient than four-valued modal algebras for the study of four-valued Monteiro propositional calculus from an algebraic point of view. This follows from the fact that the implication → is one of its basic binary operations.



Mouvement et origine du calcul infinitésimal Philosophie et continuité

Por • 29 ago, 2014 • Category: Educacion

This article has his origin in some lectures given at the University of Bologna, inside an interdisciplinary program of mathematics, history of science, physics and philosophy. Since they are at the junction of these fields, movement and infinitesimal calculus are good instances to understand some fundamental questions in history of sciences, the diversity of the conceptions stretching across it and more generally the philosophy background of theses researches. It is the field where the ‘struggle of giants’ takes place. In this article we consider the general foundations needed for this study, in particular its philosophical background. While the principal question concerns ‘the one and the multiple’ it is treated through the study of the ‘discreet and the continuous’ considered under both his philosophical and mathematical aspect. In a second article we will consider the relation between the theorization of the movement and the infinitesimal calculus, and their historical background where they were able to grow



Bourdieu Dynamics of Fields from a Modified Axelrod Model

Por • 28 ago, 2014 • Category: sociologia

Pierre Bourdieu discussed how an individual’s taste relates o his or her social environment, and how the classification of distinct and vulgar, among others, arises from at the same time as shapes this taste in his work called La Distinction. Robert Axelrod created a computational model with local convergence and global polarization properties to describe the dissemination of culture by simple selective interactions. In this letter, Axelrod model is modified, while holding to the same original principles, to describe Bourdieu theory. This allows to analyze how the dynamics of society’s tastes and trends may vary with a simple approach, considering social structures and to understand which social forces are crucial to change dynamics.



Pure exact structures and the pure derived category of a scheme

Por • 28 ago, 2014 • Category: Educacion

Let C be closed symmetric monoidal Grothendieck category. We define the pure derived category with respect to the monoidal structure via a relative injective model category structure on the category C(C) of unbounded chain complexes in C . We use λ -Purity techniques to get this. As application we define the stalkwise pure derived category of the category of quasi–coherent sheaves on a quasi-separated scheme. We also give a different approach by using the category of flat quasi–coherent sheaves



Weak Poincaré Inequality for Convolution Probability Measures

Por • 28 ago, 2014 • Category: Crítica

Weak Poincare inequalities are established for convolution measures by using Lyapunov conditions, and new Lyapunov function is constructed. The stability for weak Poincare inequalities under convolution with compactly supported probability measures are discussed. Detailed examples are included to show the power of the main relsult.