Hemeroteca del mes enero, 2013

Carta del presidente Chávez a la Celac

Por • 30 ene, 2013 • Category: Nacionales

El presidente venezolano, Hugo Chávez Frías, envió una carta a los representantes de los países presentes en la Cumbre de Estados Latinoamericanos y Caribeños (Celac), que se celebra este lunes en Santiago de Chile. La misiva fue leída por el Vicepresidente Ejecutivo, Nicolás Maduro.



Virtual water controlled demographic growth of nations

Por • 30 ene, 2013 • Category: Economía

Population growth is in general constrained by food production, which in turn depends on the access to water resources. At a country level, some populations use more water than they control because of their ability to import food and the virtual water required for its production. Here, we investigate the dependence of demographic growth on available water resources for exporting and importing nations. By quantifying the carrying capacity of nations based on calculations of the virtual water available through the food trade network, we point to the existence of a global water unbalance. We suggest that current export rates will not be maintained and consequently we question the long-run sustainability of the food trade system as a whole.



Uncertainty, incompleteness, chance, and design

Por • 30 ene, 2013 • Category: Filosofía

The 20th century has revealed two important limitations of scientific knowledge. On the one hand, the combination of Poincar\’e’s nonlinear dynamics and Heisenberg’s uncertainty principle leads to a world picture where physical reality is, in many respects, intrinsically undetermined. On the other hand, G\”odel’s incompleteness theorems reveal us the existence of mathematical truths that cannot be demonstrated. More recently, Chaitin has proved that, from the incompleteness theorems, it follows that the random character of a given mathematical sequence cannot be proved in general (it is ‘undecidable’). I reflect here on the consequences derived from the indeterminacy of the future and the undecidability of randomness, concluding that the question of the presence or absence of finality in nature is fundamentally outside the scope of the scientific method.



About the Infinite Repetition of Histories in Space

Por • 29 ene, 2013 • Category: Ambiente

This paper analyzes two different proposals, one by Ellis and Brundrit, based on classical relativistic cosmology, the other by Garriga and Vilenkin, based on the DH interpretation of quantum mechanics, both of which conclude that, in an infinite universe, planets and living beings must be repeated an infinite number of times. We point to some possible shortcomings in the arguments of these authors. We conclude that the idea of an infinite repetition of histories in space cannot be considered strictly speaking a consequence of current physics and cosmology. Such ideas should be seen rather as examples of {\guillemotleft}ironic science{\guillemotright} in the terminology of John Horgan.



Mala música y peor comida

Por • 29 ene, 2013 • Category: Nacionales

¿Qué debemos hacer para disponer de alimentos variados, a precio razonable y en cantidad adecuada?



Inflación 2013

Por • 29 ene, 2013 • Category: Nacionales

Ahora se presenta el riesgo de entrar en una hiperinflación



The hypothesis of urban scaling: formalization, implications and challenges

Por • 29 ene, 2013 • Category: sociologia

There is strong expectation that cities, across time, culture and level of development, share much in common in terms of their form and function. Recently, attempts to formalize mathematically these expectations have led to the hypothesis of urban scaling, namely that certain properties of all cities change, on average, with their size in predictable scale-invariant ways. The emergence of these scaling relations depends on a few general properties of cities as social networks, co-located in space and time, that conceivably apply to a wide range of human settlements. Here, we discuss the present evidence for the hypothesis of urban scaling, some of the methodological issues dealing with proxy measurements and units of analysis and place these findings in the context of other theories of cities and urban systems. We show that a large body of evidence about the scaling properties of cities indicates, in analogy to other complex systems, that they cannot be treated as extensive systems and discuss the consequences of these results for an emerging statistical theory of cities.



Historical Approach to Physics according to Kant, Einstein, and Hegel

Por • 28 ene, 2013 • Category: Crítica

It is known that Einstein’s conceptual base for his theory of relativity was the philosophy formulated by Immanuel Kant. Things appear differently to observers in different frames. However, Kant’s Ding-an-Sich leads to the existence of the absolute reference frame which is not acceptable in Einstein’s theory. It is possible to avoid this conflict using the ancient Chinese philosophy of Taoism where two different views can co-exist in harmony. This is not enough to explain Einstein’s discovery of the mass-energy relation. The energy-momentum relations for slow and ultra-fast particles take different forms. Einstein was able to synthesize these two formulas to create his energy-mass relation. Indeed, this is what Hegelianism is about in physics. Isaac Newton synthesized open orbits for comets and closed orbits for planets to create his second law of motion. Maxwell combined electricity and magnetism to create his four equations to the present-day wireless world. In order to synthesize wave and particle views of matter, Heisenberg formulated his uncertainty principle. Relativity and quantum mechanics are the two greatest theories formulated in the 20th Century. Efforts to synthesize these two theories are discussed in detail.



Is a tabletop search for Planck scale signals feasible?

Por • 28 ene, 2013 • Category: Educacion

Quantum gravity theory is untested experimentally. Could it be tested with tabletop experiments? While the common feeling is pessimistic, a detailed inquiry shows it possible to sidestep the onerous requirement of localization of a probe on Planck length scale. I suggest a tabletop experiment which, given state of the art ultrahigh vacuum and cryogenic technology, could already be sensitive enough to detect Planck scale signals. The experiment combines a single photon’s degree of freedom with one of a macroscopic probe to test Wheeler’s conception of “quantum foam”, the assertion that on length scales of the order Planck’s, spacetime is no longer a smooth manifold. The scheme makes few assumptions beyond energy and momentum conservations, and is not based on a specific quantum gravity scheme.



Escenarios al regreso de Chávez

Por • 28 ene, 2013 • Category: Nacionales

En aras de contribuir con el necesario debate político sobre el futuro del proceso revolucionario y la construcción del socialismo bolivariano en nuestro país, a continuación me permito prefigurar tres escenarios post -retorno y asumir una postura ante ellos.