Hemeroteca del mes septiembre, 2012

Distance weighted city growth

Por • 21 sep, 2012 • Category: sociologia

Urban agglomerations exhibit complex emergent features of which Zipf’s law, i.e. a power-law size distribution, and fractality may be regarded as the most prominent ones. We propose a simplistic model for the generation of city-like structures which is solely based on the assumption that growth is more likely to take place close to inhabited space. The model involves one parameter which is an exponent determining how strongly the attraction decays with the distance. In addition, the model is run iteratively so that existing clusters can grow and new ones can emerge. The model is capable of reproducing the size distribution and the fractality of the hull of the largest cluster. While the power-law distribution depends on both, the imposed exponent and the iteration, the fractality seems to be independent of the former and only depends on the latter.

Joint Scaling Theory of Human Dynamics and Network Science

Por • 19 sep, 2012 • Category: sociologia

The increasing availability of large-scale data on human behavior has catalyzed simultaneous advances in network theory, capturing the scaling properties of the interactions between a large number of individuals, and human dynamics, quantifying the temporal characteristics of human activity patterns. These two areas remain disjoint, however, traditionally each pursuing as a separate modeling framework. Here we establish the first formal link between these two areas by showing that the exponents characterizing the degree and link weight distribution in social networks can be expressed in terms of the dynamical exponents characterizing human activity patterns. We test the validity of these theoretical predictions on datasets capturing various facets of human interactions, from mobile calls to tweets. We find evidence of a universal measure, that links networks and human dynamics, but whose value is independent of the means of communication, capturing a fundamental property of human activity.
arXiv:1209.1411v1 [physics.soc-ph]

The different paths to entropy

Por • 19 sep, 2012 • Category: Ciencia y tecnología

In order to undestand how the complex concept of entropy emerged,we propose a trip towards the past reviewing the works of Clausius, Boltzmann, Gibbs and Planck. In particular, since the Gibbs’s work is not very well known, we present a detailed analysis, recalling the three definitions of the entropy that Gibbs gives. May be one of the most important aspect of the entropy is to see it as a thermodynamic potential like the other thermodynamic potentials as proposed by Callen. We close with some remarks on entropy and irreversibility.

Da Gauss a Einstein

Por • 19 sep, 2012 • Category: Ambiente

The present short essay, of essentially historical nature, aims at describing the transition from the Euclidean-Newtonian space-time geometry of Classical Physics to the Pseudoriemannian geometry of General Relativity, including the Minkowskian geometry of Special Relativity as an intermediate step.

A basic formula for prime numbers

Por • 19 sep, 2012 • Category: Educacion

The set of prime numbers has been analyzed, based on their algebraic and arithmetical structure. Here by obtaining a basic formula for prime numbers, they are identified, and it has been shown that prime numbers, under a special and systematic procedure, are combinations (unions and intersections) of some subsets of natural numbers, with elementary structures. In fact, logical essence of obtained formula for prime numbers is quite similar to formula 2n for even numbers and formula 2n -1 for odd numbers. Usually the prime numbers appear complex and irregular, here they have been described and more clarified, and finally specified examples for obtained formula are presented.

Venezuela-China: relación dinámica y estratégica

Por • 18 sep, 2012 • Category: Nacionales

Muchos países latinoamericanos se quejan de una relación desigual con China, la cual los está conduciendo a la condición de simples proveedores de commodities. No puede decirse que éste sea el caso de Venezuela. No sólo por la magnitud y la naturaleza estratégica de los proyectos involucrados, sino por el hecho de que China se ha abocado a la fabricación local de manufacturas que de otra manera vendería directamente. Esto último no sólo se traduce en el ahorro de divisas sino que transfiere tecnología y crea puestos de trabajo en el país receptor. Si este modelo fuese reproducido a lo largo de la región muchas de las quejas planteadas sin duda alguna amainarían.

Measurement Theory in the Philosophy of Science

Por • 18 sep, 2012 • Category: Filosofía

The philosophy of science is a discipline concerning the metaphysical aspect of science. Recently, I proposed measurement theory, which is characterized as the metaphysical and linguistic interpretation of quantum mechanics. I assert that this theory is one of the most fundamental languages in science, and thus, it is located at the central position in science. This assertion will be examined throughout this preprint, which is written as the draft of my future book (concerning the philosophy of science). Hence, I hope to hear various opinions about this draft.

Lattice Gauge Theory and the Origin of Mass

Por • 18 sep, 2012 • Category: Opinion

Most of the mass of everyday objects resides in atomic nuclei; the total of the electrons’ mass adds up to less than one part in a thousand. The nuclei are composed of nucleons—protons and neutrons—whose nuclear binding energy, though tremendous on a human scale, is small compared to their rest energy. The nucleons are, in turn, composites of massless gluons and nearly massless quarks. It is the energy of these confined objects, via $M=E/c^2$, that is responsible for everyday mass. This article discusses the physics of this mechanism and the role of lattice gauge theory in establishing its connection to quantum chromodynamics.

Nuestra opinión sobre el momento político actual y la batalla del 7 de octubre de 2012

Por • 18 sep, 2012 • Category: Nacionales

Una batalla que debe ser como la definió una vez Simón Bolívar en Carabobo, espléndida porque facilitó la derrota del ejército de Morillo y su desenlace final en Ayacucho en 1824, contundente y demoledora para las fuerzas de la antipatria como lo señala el Presidente Chávez y el Comando Carabobo.

Guerra civil de Chávez

Por • 15 sep, 2012 • Category: Nacionales

Para el caso de los grupos armados organizados: ¿Con que nos amenaza Chávez si pierde? Con los 5 colectivos armados que tiene alrededor de Miraflores, plenamente identificados, que han exhibido armas de guerra pública y comunicacionalmente? Con eso no se hace una guerra civil, señor Chávez