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sexta-feira, janeiro 08, 2010

Darwinismo Quantico e analogias biológicas

Talvez um dos problemas associados com o Darwinismo ao longo de sua história seja que ele representa um algoritmo tão geral que analogias e metáforas podem ser feitas em profusão, com maior ou menor fidelidade ao conceito original. O Darwinismo Social começa como uma metáfora e termina como ideologia.

E essa ideologia de forma alguma está morta: você pode vê-la com facilidade na seção de cartas da revista Veja, por exemplo, onde os emergentes são "ajustados (fit) socialmente" e os pobres são "desajustados (unfit) socialmente, são pobres por que têm muitos filhos, e assim continuam a espalhar a pobreza" (como se existisse o gene da pobreza!).

O mais engraçado é que, em termos Darwinistas, quem tem muitos filhos é que são os ajustados (alto fitness) enquanto que quem tem poucos filhos têm baixo fitness biológico. E é aí que reside todo o dilema da estabilização da população mundial: os países com taxa demográfica estável ou decrescente têm baixo fitness, não importa sua riqueza. Israel vai enfrentar a bomba demográfica palestina em 20 anos. A Europa vai se islamizar, e o Japão vai definhar frente à China. Os pobres herdarão a Terra... E mesmo o Brasil corre o risco de ficar velho antes de ficar rico.

Por incrível que pareça, são os anti-Darwinistas da direita religiosa conservadora americana, com sua ênfase na família etc., que são favorecidos pelo fitness Darwinista. O avanço demográfico desse pessoal é que produziu a revolução conservadora de Reagan a Bush. Não está claro que Obama e os democratas consigam resistir a esse efeito demográfico no longo prazo...

O artigo abaixo não tem nada a ver com isso. É apenas um exemplo de como a Física e a Biologia trocam metáforas e analogias entre si...

Thursday, January 07, 2010

Quantum Darwinism can explain the nature of classical reality. But is it really a form of natural selection or just an imposter?


Quantum darwinism is an extraordinary idea that was unleashed last year by the physicist by Wojciech Zurek at Los Alamos National Labs in New Mexico.

It's main claim is that it explains the quantum-classical transition: why macroscopic physics obeys classical rules while the quantum world obeys the seemingly weird laws of quantum mechanics. That makes it a Big Idea.

So how does it work? Zurek's way into this problem is to think about the role of the environment in quantum mechanics. For other quantum physicists, the environment has never been anything more than a nuisance. Consider a quantum object in isolation and the quantum information it contains can survive forever. But place it in the real world and this quantum information leaks into the environment, destroying the system under study.

Zurek takes different view. He thinks of the environment as an information channel and the properties of this channel are the key to understanding quantum darwinism.

All macroscopic measuring machines get their information through this channel. For example, at this very moment you are intercepting a fraction of the photons emitted by a screen. But we can never observe all of the environment, only a small fraction of it which reveal systems of interest.

This is the essence of quantum darwinism, says Zurek. Only quantum states that can be transmitted through the environment in the right kind of way and with multiple copies, can be observed on the macroscopic scale. That rules out various kinds of quantum information. What's left are what Zurek calls "pointer states". These are what we observe classically.

So the classical view of the universe is determined by the states that survive transmission through the environmental information channel. Hence the darwinism: it is only possible to observe the states that are fit enough to survive this process of transmission.

But is this real survival of the fittest or just something like it? That's the question raised today by the independent researcher John Campbell.

It has long been known that Darwin's theory of natural selection can be applied in many situations. The "substrate free" version of it is called universal darwinism and is essentially an algorithm composed of three steps: replication or copying, variations amongst the copies, and selective survival of the copies determined by which variations they possess.

Campbell's conclusion is that quantum darwinism meets this criteria.

That still leaves many questiosn unanswered, of course. In his paper introducing quantum darwinism, Zurek asks: "Is Quantum Darwinism (a process of multiplication of information about certain favored states that seems to be a fact of quantum life") in some way behind the familiar natural selection? I cannot answer this question, but neither can I resist raising it."

Campbell would have us believe that they are intimately linked, although this conclusion is by no means a slam dunk.

There's plenty of inspiring work to be done here by any philosophers with a little time on their hands.

Ref: arxiv.org/abs/1001.0745: Quantum Darwinism as a Darwinian process

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