sabato 11 settembre 2010

Hawking's Nobel

Some people have argued that the inner radius of a black hole is not a physical, i.e. measurable, quantity. In fact I share that view, seeing no reason why the inner radius should coincide with the radius apparent to an observer on this side of the horizon. If those arguments are correct, they empty Hawking's theory of black hole radiation of any physical content, since its predictions would depend on a free parameter. On the other hand, should black hole radiation be detected, those arguments would be proven erroneous.

venerdì 23 luglio 2010

Fabulous accuracy

It is widely claimed that quantum field theory (as many-body perturbation theory is commonly referred to) provides, via renormalization, fantastically precise predictions of experimental results, both in phase transitions and in particle physics. However the relevant series are notoriously divergent, so that Borel transformations are used to extract satisfactory results.
For phase transitions the commonly cited works are those of Zinn-Justin and coworkers, which however rely on several additional adjustable parameters. In his survey [1] Zinn-Justin states with crystalline openness: "rho is a free parameter, adjusted empirically to improve the convergence of the transformed series ... Eventually the method has been refined, which involves also introducing two additional free parameters. ... It is clear from these remarks that the errors quoted in the final results are educated guesses based on large numbers of consistency checks.". While quotes out of context can be deceptive, personally I am left with some doubts about the predictive character of the theory.
[1] Jean Zinn-Justin, Phase Transitions and Renormalization Group from Theory to Numbers, Séminaire Poincaré 2, 2002, 55-74 (link).

giovedì 21 gennaio 2010

Ex nihilo

From Darwinist tautologies to decoherence theory's unphysical hidden assumptions, spontaneous morphogenesis appears as the founding myth of modern "scientific" ontology.