Hemeroteca del mes enero, 2012

The Philosophy behind Quantum Gravity

Por • 31 ene, 2012 • Category: Filosofía

This paper investigates some of the philosophical and conceptual issues raised by the search for a quantum theory of gravity. It is critically discussed whether such a theory is necessary in the first place, and how much would be accomplished if it is eventually constructed. I argue that the motivations behind, and expectations to, a theory of quantum gravity are entangled with central themes in the philosophy of science, in particular unification, reductionism, and the interpretation of quantum mechanics. I further argue that there are —contrary to claims made on behalf of string theory— no good reasons to think that a quantum theory of gravity, if constructed, will provide a theory of everything, that is, a fundamental theory from which all physics in principle can be derived.

On Structure and Organization: An Organizing Principle

Por • 31 ene, 2012 • Category: Opinion

We discuss the nature of structure and organization, and the process of making new Things. Hyperstructures are introduced as binding and organizing principles, and we show how they can transfer from one situation to another. A guiding example is the hyperstructure of higher order Brunnian rings and similarly structured many-body systems.

Constructivist and Structuralist Foundations: Bishop’s and Lawvere’s Theories of Sets

Por • 31 ene, 2012 • Category: Educacion

Bishop’s informal set theory is briefly discussed and compared to Lawvere’s Elementary Theory of the Category of Sets (ETCS). We then present a constructive and predicative version of ETCS, whose standard model is based on the constructive type theory of Martin-L\»of. The theory, CETCS, provides a structuralist foundation for constructive mathematics in the style of Bishop.

A Historical Profile of the Higgs Boson

Por • 31 ene, 2012 • Category: Ciencia y tecnología

The Higgs boson was postulated in 1964, and phenomenological studies of its possible production and decays started in the early 1970s, followed by studies of its possible production in e+ e-, pbar p and pp collisions, in particular. Until recently, the most sensitive searches for the Higgs boson were at LEP between 1989 and 2000, which have been complemented by searches at the Fermilab Tevatron. The LHC has recently entered the hunt, excluding a Higgs boson over a large range of masses and revealing a tantalizing hint in the range 119 to 125 GeV, and there are good prospects that the existence or otherwise of the Higgs boson will soon be established. One of the most attractive possibilities is that the Higgs boson is accompanied by supersymmetry, though composite options have yet to be excluded. This article reviews some of the key historical developments in Higgs physics over the past half-century.

Logic and Categories As Tools For Building Theories

Por • 28 ene, 2012 • Category: Filosofía

We give a short introduction to category theory aimed at philosophers. We emphasize methodological issues and philosophical ramifications.

The relation between classical and quantum electrodynamics

Por • 28 ene, 2012 • Category: Ambiente

Quantum electrodynamics presents intrinsic limitations in the description of physical processes that make it impossible to recover from it the type of description we have in classical electrodynamics. Hence one cannot consider classical electrodynamics as reducing to quantum electrodynamics and being recovered from it by some sort of limiting procedure. Quantum electrodynamics has to be seen not as a more fundamental theory, but as an upgrade of classical electrodynamics, which permits an extension of classical theory to the description of phenomena that, while being related to the conceptual framework of the classical theory, cannot be addressed from the classical theory.

The workings of the Maximum Entropy Principle in collective human behavior

Por • 27 ene, 2012 • Category: sociologia

We exhibit compelling evidence regarding how well does the MaxEnt principle describe the rank-distribution of city-populations via an exhaustive study of the 50 Spanish provinces (more than 8000 cities) in a time-window of 15 years (1996-2010). We show that the dynamics that governs the population-growth is the deciding factor that originates the observed distributions. The connection between dynamics and distributions is unravelled via MaxEnt.

The Conundrum of Iran

Por • 27 ene, 2012 • Category: Política

At the moment, maintaining the status quo is not in the US interests, holds Stratfor, a US-based global intelligence agency: “If al Assad survives and if the situation in Iraq proceeds as it has been proceeding, then Iran is creating a reality that will define the region. The United States does not have a broad and effective coalition, and certainly not one that would rally in the event of war. It has only Israel …” (2) If the conflict with Iran takes the shape of a protracted bombing campaign and comes as a prologue to the occupation of the country, the US will need to strengthen its positions in adjacent regions, meaning that Washington will be trying to draw the Caucasian republics (Georgia, Azerbaijan) and those of Central Asia into the orbit of its policy and thus tightening the “Anaconda loop” around Russia.

La genialidad de Chávez

Por • 27 ene, 2012 • Category: Nacionales

Venezuela constituye un brillante ejemplo del rol teórico y práctico que los militares revolucionarios pueden desempeñar en la lucha por la independencia de nuestros pueblos, como ya lo hicieron hace dos siglos bajo la genial dirección de Simón Bolívar. Chávez, un militar venezolano de humilde origen, irrumpe en la vida política de Venezuela inspirado en las ideas del libertador de América. Sobre Bolívar, fuente inagotable de inspiración, Martí escribió: “ganó batallas sublimes con soldados descalzos y medio desnudos […] jamás se peleó tanto, ni se peleó mejor, en el mundo por la libertad…” Pero el líder bolivariano no se limita a la elaboración teórica. Sus medidas concretas no se hacen esperar. Los países caribeños de habla inglesa, a los que modernos y lujosos buques cruceros yankis le disputaban el derecho a recibir turistas en sus hoteles, restaurantes y centros de recreación, no pocas veces de propiedad extranjera pero que al menos generaban empleo, agradecerán siempre a Venezuela el combustible suministrado por ese país con facilidades especiales de pago, cuando el barril alcanzó precios que a veces superaban los 100 dólares.

Rangel Silva ratifica reunión con su par colombiano para el 10 de febrero

Por • 27 ene, 2012 • Category: Nacionales

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