Hemeroteca del mes julio, 2012

Venezuela debe ajustar políticas económicas

Por • 28 jul, 2012 • Category: Nacionales

Especialistas dicen que control cambiario puede mantenerse si no afecta la libre competencia

A Biography of Henri Poincaré – 2012 Centenary of the Death of Poincaré

Por • 28 jul, 2012 • Category: sociologia

On January 4, 2012, the centenary of Henri Poincar\’e’s death, a colloquium was held in Nancy, France the subject of which was «Vers une biographie d’Henri Poincar\’e». Scholars discussed several approaches for writing a biography of Poincar\’e. In this paper I present a personal and scientific biographical sketch of Poincar\’e, which does not in any way reflect Poincar\’e’s rich personality and immense activity in science: When Poincar\’e traveled to parts of Europe, Africa and America, his companions noticed that he knew well everything from statistics to history and curious customs and habits of peoples. He was almost teaching everything in science. He was so encyclopedic that he dealt with the outstanding questions in the different branches of physics and mathematics; he had altered whole fields of science such as non-Euclidean geometry, Arithmetic, celestial mechanics, thermodynamics and kinetic theory, optics, electrodynamics, Maxwell’s theory, and other topics from the forefront of Fin de Si\`ecle physical science. It is interesting to note that as opposed to the prosperity of biographies and secondary papers studying the life and scientific contributions of Albert Einstein, one finds much less biographies and secondary sources discussing Poincar\’e’s life and work.

Chávez dice que asalto al Cuartel Moncada fundó lucha de liberación en el mundo

Por • 26 jul, 2012 • Category: Nacionales

El asalto al Cuartel Moncada, “liderado por el comandante Fidel Castro, fue el acto fundador para la lucha de liberación nacional de los pueblos de América Latina y del mundo”, dijo Chávez en un comunicado.

Statistics, Causality and Bell’s theorem

Por • 26 jul, 2012 • Category: Ambiente

Bell’s (1964) theorem is popularly supposed to establish the non-locality of quantum physics as a mathematical-physical theory. Building from this, observed violation of Bell’s inequality in experiments such as that of Aspect and coworkers (1982) is popularly supposed to provide empirical proof of non-locality in the real world. This paper reviews recent work on Bell’s theorem, linking it to issues in causality as understood by statisticians. The paper starts with a new proof of a strong (finite sample) version of Bell’s theorem which relies only on elementary arithmetic and (counting) probability.

A proof of Bell’s inequality in quantum mechanics using causal interactions

Por • 26 jul, 2012 • Category: Ciencia y tecnología

We give a simple proof of Bell’s inequality in quantum mechanics which, in conjunction with experiments, demonstrates that the local hidden variables assumption is false. The proof sheds light on relationships between the notion of causal interaction and interference between particles.

A Note on the Prehistory of Superheavy Elements

Por • 26 jul, 2012 • Category: Educacion

Artificially produced chemical elements heavier than uranium have been known for more than seventy years and the number of superheavy elements continues to grow. Presently 26 transuranic elements are known. This paper examines the earliest scientific interest in the very heavy elements and the related question of an upper limit of the periodic system. In the period from the 1880s to the early 1930s, three kinds of questions appealed to a minority of physicists and chemists: (1) Why is uranium the heaviest known element? (2) Do there exist transuranic or superheavy elements elsewhere in the universe? (3) Is there a maximum number of elements, corresponding to a theoretical limit for the periodic system? The early attempts to answer or clarify these questions lacked a foundation in nuclear physics, not to mention the total lack of experimental evidence, which explains why most of them were of a speculative nature. Although the speculations led no nothing, they are interesting in their own right and deserve a place in the history of the physical sciences.

Two Paths to Infinite Thought: Alain Badiou and Jacques Derrida on the Question of the Whole

Por • 25 jul, 2012 • Category: Filosofía

This essay defends an idea that is no longer fashionable: that there is a whole. The motivation for a defense of this notion has nothing to do with intellectual conservatism or a penchant for Hegel. Rather, what we hope to establish is a second path into what Alain Badiou has called the ‘Cantorian Revolution’. In order to open this path we undertake a three-fold task. First, we deconstruct Badiou’s onto-logical project by isolating the suppressed significance of Ernst Zermelo. This point allows us to recover a Cantorian possibility for addressing the infinite as an inconsistent whole. Second, we turn to work by the logician Graham Priest in order to remove the absurdity of discussing true contradictions. Finally, we return to Jacques Derrida’s early work on Husserl in order to chart a phenomenological path to an affirmation of an inconsistent whole. We close, then, with the implications for contemporary philosophy.

Predicting Efficiency in master-slave grid computing systems

Por • 23 jul, 2012 • Category: sociologia

This work reports a quantitative analysis to predicting the efficiency of distributed computing running in three models of complex networks: Barab\’asi-Albert, Erd\H{o}s-R\’enyi and Watts-Strogatz. A master/slave computing model is simulated. A node is selected as master and distributes tasks among the other nodes (the clients). Topological measurements associated with the master node (e.g. its degree or betwenness centrality) are extracted and considered as predictors of the total execution time. It is found that the closeness centrality provides the best alternative. The effect of network size was also investigated.

In search of lost spacetime: philosophical issues arising in quantum gravity

Por • 21 jul, 2012 • Category: Filosofía

This essay presents an accessible introduction to the basic motivations to seek a quantum theory of gravity. It focuses on one approach- loop quantum gravity – as an example of the rich philosophical issues that arise when we try to combine spacetime and quantum physics.

The mystery of relationship of mechanics and field in the many-body quantum world

Por • 21 jul, 2012 • Category: Ciencia y tecnología

Bohr’s complementarity, observed at the single-particle level, extends also to the nature of composite systems that can run under both mechanical as well as the field pattern. The Born-Oppenheimer approximation, despite its success and widespread use, is a merely pragmatic rule, and not the law of nature. It tries to solve under the mechanical pattern the hierarchy from atoms to molecules, which is reserved only for the field pattern. The gateway from the mechanical into the field pattern should be determined in order correctly to deal with the center of gravity, which is under the field pattern «materialized» in the form of new quasipartiles – rotons and translons. Until the J-T effect will be formulated and understood on the basis of the field pattern, we will never understand the principle of superconductivity. The correct criterion if the Jahn-Teller effect in a given system manifests itself or not, is determined via the matrix elements of electron-roton and electron-translon interactions. The «field» symmetry may differ from the «mechanical» symmetry, and this enigma is intrinsic just to superconductors. The small light electron can interact via the electron-roton and electron-translon interaction with the whole macroscopic crystal. And just here we can find the true explanation, why superconductivity is a microscopic effect on macroscopic level.