Ajuste fino, mas não em um campo de golfe!
Se o landscape de possíveis universos é do tipo campo de golfe (apenas umas poucas soluções puntuais) então não seria possível um Darwinismo Cosmologico à lá Smolin. Talvez esse novo paper mostre que o landscape é suave e permite um processo evolutivo. Estou testando essas idéias usando automatos celulares, mas é um projeto de final de semana que tem andado MUITO lentamente...
Stars In Other Universes: Stellar structure with different fundamental constants
(Submitted on 23 Jul 2008)
Motivated by the possible existence of other universes, with possible variations in the laws of physics, this paper explores the parameter space of fundamental constants that allows for the existence of stars. To make this problem tractable, we develop a semi-analytical stellar structure model that allows for physical understanding of these stars with unconventional parameters, as well as a means to survey the relevant parameter space. In this work, the most important quantities that determine stellar properties -- and are allowed to vary -- are the gravitational constant $G$, the fine structure constant $\alpha$, and a composite parameter $C$ that determines nuclear reaction rates. Working within this model, we delineate the portion of parameter space that allows for the existence of stars. Our main finding is that a sizable fraction of the parameter space (roughly one fourth) provides the values necessary for stellar objects to operate through sustained nuclear fusion. As a result, the set of parameters necessary to support stars are not particularly rare. In addition, we briefly consider the possibility that unconventional stars (e.g., black holes, dark matter stars) play the role filled by stars in our universe and constrain the allowed parameter space.
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