Home // Posts tagged "quantum physics"

Amit Goswami realmente existe!

Em minha palestra Ciência e Religião: Quatro Perspectivas, dada no IEA-RP, chamei de pseudocientífica toda crença que  afirma que possui evidências científicas a seu favor quando esse não é exatamente o caso. O melhor que uma opinião filosófica, ideológica ou religiosa deve afirmar é que ela é “compatível com” e não “derivada do” conhecimento científico. Essa também é a posição de Freeman Dyson.

Durante a palestra, fiz uma crítica a Amit Goswami que se revelou mais tarde bastante errada, e devo aqui registrar um “erramos” ou mea culpa.  Pelo fato de que Goswami não tem uma página na Wikipedia inglesa (mas apenas na Portuguesa) e devido a ter feito uma busca na Web of Science que não revelou nenhum artigo de física desse autor, fiz a inferência apressada de que talvez Amit Goswami fosse um pseudônimo de uma personagem menor (assim como Acharya S. é o pseudônimo de Dorothy M. Murdock, a propagadora da teoria da conspiração do Cristo Mítico).

Creio que os editores da Wikipedia foram demasiado rigorosos com Goswami. Afinal, embora ele seja um físico não notável, com índice de Hirsch igual a sete, ele pelo menos tem um PhD e é autor de um livro-texto sério de Física Quântica.  Sua migração para a New Age, seguindo os passos de Fritjof Capra, longe de ser um demérito, pode refletir grande inteligência social e financeira (ironia aqui!).  Assim, se deletaram Goswami da Wikipedia, deveriam deletar Acharya S. também, por coerência!

Wikipedia:Articles for deletion/Amit Goswami

From Wikipedia, the free encyclopedia
The following discussion is an archived debate of the proposed deletion of the article below. Please do not modify it. Subsequent comments should be made on the appropriate discussion page (such as the article’s talk page or in a deletion review). No further edits should be made to this page.

The result was delete. Guillaume2303’s research indicates that the early “keep” opinions likely apply to another, more notable person of the same name, which means that they are not taken into consideration here. The “keep” opinions by Jleibowitz101 and 159.245.32.2 are also not taken into account as they are not based on our inclusion rules and practices.  Sandstein  06:25, 11 April 2012 (UTC)

Amit Goswami

Amit Goswami (edit|talk|history|links|watch|logs) – (View log)
(Find sources: “Amit Goswami” – news · books · scholar · JSTOR · free images)

I’m just not convinced this article really demonstrates notability. He played a small role in a couple films, he wrote books outside his field for very minor publishers, and… er, that’s about it. I’m just not buying it, and the lack of good WP:RS – this has major primary sourcing issues – is another mark against it. Perhaps something can be salvaged, but I’m not convinced the case has been made. ETA: Guillaume2303’s point (below) that there are multiple people of this name, and this article appears to be on the much less notable one is rather significant. 86.** IP (talk) 21:07, 3 April 2012 (UTC) Read more [+]

Palestra no Instituto de Estudos Avançados (RP) sobre Ciência e Religião

 

sexta-feira, 9 de novembro de 2012

Ciência e Religião: quatro perspectivas

Escrito por 

Data e Horário: 26/11 às 14h30
Local: Salão de Eventos do Centro de Informática de Ribeirão Preto – CIRP/USP (localização)

O evento, que será apresentado por Osame Kinouchi, discutirá quatro diferentes visões sobre a interação entre Ciência e Religião: o conflito, a separação, o diálogo e a integração. Examinando as fontes de conflito recentes (Culture Wars), o professor sugere que elas têm origem no Romantismo Anticientífico, religioso ou laico.

Segundo Osame, a ideia de separação entre os campos Religioso e Científico já não parece ser viável devido aos avanços da Ciência em tópicos antes considerados metafísicos, tais como as origens do Universo (Cosmologia), da Vida (Astrobiologia), da Mente (Neurociências) e mesmo das Religiões (Neuroteologia, Psicologia Evolucionária e Ciências da Religião).
A palestra mostrará também que tentativas de integração forçada ou prematura entre Religião e Ciência correm o risco de derivar para a Pseudociência. Sendo assim, na visão do professor, uma posição mais acadêmica de diálogo de alto nível pode ser um antídoto para uma polarização cultural ingênua entre Ateísmo e Religiosidade.

Vídeo do evento

O melhor livro de divulgação científica que encontrei em quarenta anos de leituras

Depois escrevo minha resenha…

A REALIDADE OCULTA – Universos paralelos e as leis profundas do cosmo
Brian Greene
R$ 59,00 Comprar
R$ 39,00 E-Book
Indique Comente
É necessário estar logado para utilizar este recurso. Acompanhe

Meio século atrás, os cientistas encaravam com ironia a possibilidade de existirem outros universos além deste que habitamos. Tal hipótese não passava de um delírio digno de Alice no País das Maravilhas – e que, de todo modo, jamais poderia ser comprovada experimentalmente. Os desafios propostos pela Teoria da Relatividade e pela física quântica para o entendimento de nosso próprio universo já eram suficientemente complexos para ocupar gerações e gerações de pesquisadores. Entretanto, diversos estudos independentes entre si, conduzidos por cientistas respeitados em suas áreas de atuação – teoria das cordas, eletrodinâmica quântica, teoria da informação -, começaram a convergir para o mesmo ponto: a existência de universos paralelos – o multiverso – não só é provável como passou a ser a explicação mais plausível para diversos enigmas cosmológicos.
Em A realidade oculta, Brian Greene – um dos maiores especialistas mundiais em cosmologia e física de partículas – expõe o fantástico desenvolvimento da física do multiverso ao longo das últimas décadas. O autor de O universo elegante passa em revista as diferentes teorias sobre os universos paralelos a partir dos fundamentos da relatividade e da mecânica quântica. Por meio de uma linguagem acessível e valendo-se de numerosas figuras explicativas, Greene orienta o leitor pelos labirintos da realidade mais profunda da matéria e do pensamento.

“Se extraterrestres aparecessem amanhã e pedissem para conhecer as capacidades da mente humana, não poderíamos fazer nada melhor que lhes oferecer um exemplar deste livro.” – Timothy Ferris, New York Times Book Review

Determinando se vivemos dentro da Matrix

The Measurement That Would Reveal The Universe As A Computer Simulation

If the cosmos is a numerical simulation, there ought to be clues in the spectrum of high energy cosmic rays, say theorists

1 comment

THE PHYSICS ARXIV BLOG

Wednesday, October 10, 2012

One of modern physics’ most cherished ideas is quantum chromodynamics, the theory that describes the strong nuclear force, how it binds quarks and gluons into protons and neutrons, how these form nuclei that themselves interact. This is the universe at its most fundamental.

So an interesting pursuit is to simulate quantum chromodynamics on a computer to see what kind of complexity arises. The promise is that simulating physics on such a fundamental level is more or less equivalent to simulating the universe itself.

There are one or two challenges of course. The physics is mind-bogglingly complex and operates on a vanishingly small scale. So even using the world’s most powerful supercomputers, physicists have only managed to simulate tiny corners of the cosmos just a few femtometers across. (A femtometer is 10^-15 metres.)

That may not sound like much but the significant point is that the simulation is essentially indistinguishable from the real thing (at least as far as we understand it).

It’s not hard to imagine that Moore’s Law-type progress will allow physicists to simulate significantly larger regions of space. A region just a few micrometres across could encapsulate the entire workings of a human cell.

Again, the behaviour of this human cell would be indistinguishable from the real thing.

It’s this kind of thinking that forces physicists to consider the possibility that our entire cosmos could be running on a vastly powerful computer. If so, is there any way we could ever know?

Today, we get an answer of sorts from Silas Beane, at the University of Bonn in Germany, and a few pals.  They say there is a way to see evidence that we are being simulated, at least in certain scenarios.

First, some background. The problem with all simulations is that the laws of physics, which appear continuous, have to be superimposed onto a discrete three dimensional lattice which advances in steps of time.

The question that Beane and co ask is whether the lattice spacing imposes any kind of limitation on the physical processes we see in the universe. They examine, in particular, high energy processes, which probe smaller regions of space as they get more energetic

What they find is interesting. They say that the lattice spacing imposes a fundamental limit on the energy that particles can have. That’s because nothing can exist that is smaller than the lattice itself.

So if our cosmos is merely a simulation, there ought to be a cut off in the spectrum of high energy particles.

It turns out there is exactly this kind of cut off in the energy of cosmic ray particles,  a limit known as the Greisen–Zatsepin–Kuzmin or GZK cut off.

This cut-off has been well studied and comes about because high energy particles interact with the cosmic microwave background and so lose energy as they travel  long distances.

But Beane and co calculate that the lattice spacing imposes some additional features on the spectrum. “The most striking feature…is that the angular distribution of the highest energy components would exhibit cubic symmetry in the rest frame of the lattice, deviating significantly from isotropy,” they say.

In other words, the cosmic rays would travel preferentially along the axes of the lattice, so we wouldn’t see them equally in all directions.

That’s a measurement we could do now with current technology. Finding the effect would be equivalent to being able to to ‘see’ the orientation of lattice on which our universe is simulated.

That’s cool, mind-blowing even. But the calculations by Beane and co are not without some important caveats. One problem is that the computer lattice may be constructed in an entirely different way to the one envisaged by these guys.

Another is that this effect is only measurable if the lattice cut off is the same as the GZK cut off. This occurs when the lattice spacing is about 10^-12 femtometers. If the spacing is significantly smaller than that, we’ll see nothing.

Nevertheless, it’s surely worth looking for, if only to rule out the possibility that we’re part of a simulation of this particular kind but secretly in the hope that we’ll find good evidence of our robotic overlords once and for all.

Ref: arxiv.org/abs/1210.1847: Constraints on the Universe as a Numerical Simulation

Um novo tipo de máquina do tempo

Quantum Time Machine Solves Grandfather Paradox


Posted: 18 Jul 2010 09:10 PM PDT

A new kind of time travel based on quantum teleportation gets around the paradoxes that have plagued other time machines, say physicists

Of all the weird consequences of quantum mechanics, one of the strangest is the notion of postselection: the ability to trigger a computation that automatically disregards certain results.

Here’s an example: suppose you have a long, tortuous expression in which there are a frighteningly large number of variables. The question you want answering is which combination of variables makes the expression logically true. And the conventional way to solve it is by brute force: try every combination of variable until you find one that works. That’s hard.

Postselection, however, makes the solution easy to find. Simply allow the variables to take any value at random and then postselect on the condition that the answer must be true. This automatically disregards any wrong’uns that come up.

Postselection is controversial because it leads to all kinds of fantastical predictions about the power of quantum computers. Nobody is quite sure if these kinds of computations are possible or how to achieve them but quantum mechanics seems to allow them.

Now postselection gets even weirder thanks to some new ideas put forward by Seth Lloyd at the Massachusetts Institute of Technology and a few buddies. They say that if you combine postselection with another strange quantum behaviour called teleportation and you can build a time machine.

Before we look at how this idea works, a quick reminder about quantum teleportation. This uses the phenomenon of entanglement to reproduce in one point in space a quantum state that previously existed at another point in space.

Lloyd and cos idea is to use postselection to make this process happen in reverse. Postselection ensures that only a certain type of state can be teleported. This immediately places a limit on the state the original particle must have been in before it was teleported. In effect, the state of this particle has travelled back in time.

What’s amazing about this time machine is that it is not plagued by the usual paradoxes of time travel, such as the grandfather paradox, in which a particle travels back in time and some how prevents itself from existing in the first place.

Lloyd’s time machine gets around this because of the probabilistic nature of quantum mechanics: anything that this time machine allows can also happen with finite probability anyway, thanks to these probabilistic laws.

Another interesting feature of this machine is that it does not require any of the distortions of spacetime that traditional time machines rely on. In these, the fabric of spacetime has to be ruthlessly twisted in a way that allows the time travel to occur. These conditions may exist in the universe’s extreme environments such as inside black holes but probably not anywhere else.

The fact that similar time machines may also be possible when quantum mechanics is pushed to its limits suggests an avenue that may prove fruitful in uniting this disparate areas of science. “Our hope is that this theory may prove useful in formulating a quantum theory of gravity,” say Lloyd and buddies.

So where might their time machine be built. That’s a tricky question too. Postselection can only occur if quantum mechanics is nonlinear, something that seems possible in theory but has never been observed in practice. All the evidence so far is that quantum mechanics is linear. In fact some theorists propose that the seemingly impossible things that postselection allows is a kind of proof that quantum mechanics must be linear.

However, if nonlinear behaviour is allowed, time travel will be possible wherever it takes place. As Lloyd and co say: “It is possible for particles (and, in principle, people) to tunnel from the future to the past. “

Fire up the Delorean.

Ref: arxiv.org/abs/1007.2615: The Quantum Mechanics Of Time Travel Through Post-Selected Teleportation

Por quem os sinos quânticos dobram?


John Bell And The Nature Of Reality


Posted: 13 Jul 2010 09:10 PM PDT

Why have so few heard of one of the great heroes of modern physics?

In 1935, Einstein and his colleagues Boris Podolsky and Nathan Rosen outlined an extraordinary paradox associated with the then emerging science of quantum mechanics.


They pointed out that quantum mechanics allows two objects to be described by the same single wave function. In effect, these separate objects somehow share the same existence so that a measurement on one immediately influences the other, regardless of the distance between them.

To Einstein, Podolsky and Rosen this clearly violated special relativity which prevents the transmission of signals at superluminal speed. Something had to give.


Despite the seriousness of this situation, the EPR paradox, as it became known, was more or less ignored by physicists until relatively recently.


Today, we call the relationship between objects that share the same existence entanglement. And it is the focus of intense interest from physicists studying everything from computing and lithography to black holes and photography.


It’s fair to say that while the nature of entanglement still eludes us, few physicists doubt that a better understanding will lead to hugely important insights into the nature of reality.

Many researchers have helped to turn the study of entanglement from a forgotten backwater into one of the driving forces of modern physics. But most of them would agree that one man can be credited with kickstarting this revolution.


This man was John Bell, a physicist at CERN for much of his career, who was incensed by the apparent contradictions and problems at the heart of quantum mechanics. In the early 60s, Bell laid the theoretical foundations for the experimental study of entanglement by deriving a set of inequalities that now now bear his name.


While Bell’s inequalities are now mainstream, Bell was more or less ignored at the time. Now Jeremy Bernstein, a physicist and writer who knew Bell, publishes a short account of the background to Bell’s work along with some interesting anecdotes about the man himself, some of which are entirely new (at least, to me). He recounts screaming arguments between Bell and his university lecturers about the nature of quantum mechanics. And says that at the time of his death in 1991, Bell had been nominated for a Nobel Prize, which he was expected to win.


That would have entirely changed Bell’s legacy. He is well remembered by many working on the foundations of quantum mechanics but not well known by people in other areas. As a good example of a scientist who took on the establishment and won, that is a shame.


Ref: arxiv.org/abs/1007.0769: A Chorus Of Bells

QED não foi demonstrada?

For a Proton, a Little Off the Top (or Side) Could Be Big Trouble

By DENNIS OVERBYE

Published: July 12, 2010

For most of us, 4 percent off around the waist — a couple of belt notches — would be a great triumph.

Chris Gash

Not so for the proton, the subatomic particle that anchors atoms and is the building block of all ordinary matter, of stars, planets and people. Physicists announced last week that a new experiment had shown that the proton is about 4 percent smaller than they thought.

Instead of celebration, however, the result has caused consternation. Such a big discrepancy, say the physicists, led by Randolf Pohl of the Max Planck Institute for Quantum Optics in Garching, Germany, could mean that the most accurate theory in the history of physics, quantum electrodynamics, which describes how light and matter interact, is in trouble.

“What you have is a result that actually shocked us,” said Paul Rabinowitz, a chemist from Princeton University, who was a member of Dr. Pohl’s team.

The results were published in Nature. Protons, of course, have not shrunk. They have been whatever size they are ever since they congealed out of a primordial soup of energy and even smaller particles — quarks and gluons — in the early moments of the Big Bang. Determining how big they are, however, is both important to fundamental physics and extremely difficult.

Unable to calculate a radius directly from theory, physicists have measured protons in different ways. One is by scattering electrons off them. Another more accurate way is by spectroscopic measurements of the wavelength of the light emitted as electrons in the atom jump from one orbit to another and using quantum theory to compute the proton’s properties.

Putting these techniques together gave an answer of about 0.8768 femtometer for the proton’s radius, just less than a quadrillionth of a meter. By comparison, a typical atom is about 100 trillionths of a meter.

Seeking more precision, Dr. Pohl and his colleagues created atoms in which the electron had been replaced by a muon, which is a sort of fat electron. Weighing about 200 times more than an electron, the muon circles its proton more closely and thus gives a better reading of the proton size. The surprise was an answer that was 4 percent smaller, 0.84184 femtometer.

When that new radius, which is 10 times more precise than previous values, was used to calculate the Rydberg constant, a venerable parameter in atomic theory, the answer was 4 percent away from the traditionally assumed value. This means there are now two contradicting values of the Rydberg constant, Dr. Pohl explained, which means there is either something wrong with the theory, quantum electrodynamics, or the experiment.

“They are completely stunned by this,” said Dr. Pohl of his colleagues. “They are working like mad. If there is a problem with quantum electrodynamics this will be an important step forward.”

The late Caltech physicist Richard Feynman called quantum electodynamics “the jewel of physics,” and it has served as a template for other theories.

One possibility is that there is something physics doesn’t know yet about muons that throws off the calculations.

Or perhaps something we just don’t know about physics. In which case, Jeff Flowers of the National Physical Laboratory in Teddington in Britain pointed out in a commentary in Nature, a new phenomenon has been discovered not by the newest $10 billion collider but by a much older trick in the book, spectroscopy.

“So, if this experimental result holds up, it is an open door for a theorist to come up with the next theoretical leap and claim their Nobel Prize,” Dr. Flowers wrote.

O próton encolheu?


07 de julho de 2010 15h19 atualizado às 16h16

comentários
6

Cientistas de um grupo internacional de pesquisas afirmara, nesta quarta-feira, que um constituinte fundamental do universo visível, o próton, é menor do que se pensava anteriormente, segundo estudo publicado na revista científica Nature.

Medições revistas reduziram em 4% o raio da partícula que, embora não pareça muito – especialmente dado o tamanho infinitesimal do próton -, em experimentos futuros pode representar um desafio a preceitos fundamentais da eletrodinâmica quântica, a teoria de como a luz e a matéria interagem, disseram os autores.

Inicialmente, a equipe internacional de 32 cientistas, chefiada por Randolf Pohl, do Instituto Max Planck em Garching, Alemanha, só queria confirmar o que já se sabia e não derrubar conceitos.

Por décadas, os físicos de partículas usavam o átomo de hidrogênio como um parâmetro para medir o tamanho dos prótons, que são parte do núcleo atômico. A vantagem do hidrogênio é sua simplicidade incomparável: um elétron circunda um único próton.

Mas, se artigo estiver correto, esta unidade de medida esteve equivocada por uma margem pequena, porém crítica. “Nós não imaginávamos que haveria um abismo entre as medidas conhecidas do próton e as nossas próprias”, diz o coautor do estudo, Paul Indelicato, diretor do Laboratório Kastler Brossel na Universidade Pierre e Marie Curie, em Paris.

O novo experimento – pelo menos 10 vezes mais preciso do que qualquer outro feito até agora – foi previsto por cientistas 40 anos atrás, mas só desenvolvimentos recentes na tecnologia o tornaram possível. O truque foi recolocar o elétron no átomo do hidrogênio com um múon – partícula com a mesma carga elétrica, mas ao mesmo tempo 200 vezes mais pesado e instável – negativo.

A massa maior do múon dá ao hidrogênio muônico um tamanho atômico menor e permite uma interação muito maior com o próton. Como resultado, a estrutura do próton pode ser sondada com mais precisão do que usando o hidrogênio normal.

Jeff Flowers, cientista do Laboratório Nacional de Física britânico em Teddington, perto de Londres, disse que o trabalho pode levar as teorias da física de partículas a um novo território.

Se o descoberto no estudo for confirmado, comentou, será preciso mais do que o multibilionário acelerador de partículas instalado no Laboratório Europeu de Física Nuclear (Cern), na Suíça, para testar o chamado Modelo Padrão, lista das partículas subatômicas que formam o Universo.

Se as medidas previamente aceitas sobre as quais centenas de cálculos foram feitos estiverem errados ou existir um problema com a própria teoria eletrodinâmica quântica, os físicos têm muito trabalho a fazer.

“Agora, os teóricos vão refazer seus cálculos e mais experimentos serão feitos para confirmar ou refutar” este estudo, disse Indelicato, antes de explicar que em dois anos será feito um novo experimento com o mesmo equipamento, “desta vez, com hélio muônico”.

AFP
AFP – Todos os direitos de reprodução e representação reservados. Clique aqui para limitações e restrições ao uso.

Acho que vamos ter que ensinar Mecânica Quântica para Biólogos…

Quantum Entanglement Holds DNA Together, Say Physicists

Posted: 27 Jun 2010 09:10 PM PDT

A new theoretical model suggests that quantum entanglement helps prevent the molecules of life from breaking apart

There was a time, not so long ago, when biologists swore black and blue that quantum mechanics could play no role in the hot, wet systems of life.

Since then, the discipline of quantum biology has emerged as one of the most exciting new fields in science. It’s beginning to look as if quantum effects are crucial in a number of biological processes, such as photosynthesis and avian navigation which we’ve looked at here and here.

Now a group of physicists say that the weird laws of quantum mechanics may be more important for life than biologists could ever have imagined. Their new idea is that DNA is held together by quantum entanglement.

That’s worth picking apart in more detail. Entanglement is the weird quantum process in which a single wavefunction describes two separate objects. When this happens, these objects effectively share the same existence, no matter how far apart they might be.

The question that Elisabeth Rieper at the National University of Singapore and a couple of buddies have asked is what role might entanglement play in DNA. To find out, they’ve constructed a simplified theoretical model of DNA in which each nucleotide consists of a cloud of electrons around a central positive nucleus. This negative cloud can move relative to the nucleus, creating a dipole. And the movement of the cloud back and forth is a harmonic oscillator.

When the nucleotides bond to form a base, these clouds must oscillate in opposite directions to ensure the stability of the stucture.

Rieper and co ask what happens to these oscillations, or phonons as physicists call them, when the base pairs are stacked in a double helix.

Phonons are quantum objects, meaning they can exist in a superposition of states and become entangled, just like other quantum objects.

To start with, Rieper and co imagine the helix without any effect from outside heat. “Clearly the chain of coupled harmonic oscillators is entangled at zero temperature,” they say. They then go on to show that the entanglement can also exist at room temperature.

That’s possible because phonons have a wavelength which is similar in size to a DNA helix and this allows standing waves to form, a phenomenon known as phonon trapping. When this happens, the phonons cannot easily escape. A similar kind of phonon trapping is known to cause problems in silicon structures of the same size.

That would be of little significance if it had no overall effect on the helix. But the model developed by Rieper and co suggests that the effect is profound.

Although each nucleotide in a base pair is oscillating in opposite directions, this occurs as a superposition of states, so that the overall movement of the helix is zero. In a purely classical model, however, this cannot happen, in which case the helix would vibrate and shake itself apart.

So in this sense, these quantum effects are responsible for holding DNA together.

The question of course is how to prove this. They say that one line of evidence is that a purely classical analysis of the energy required to hold DNA together does not add up. However, their quantum model plugs the gap. That’s interesting but they’ll need to come up with something experimentally convincing to persuade biologists of these ideas.

One tantalising suggestion at the end of their paper is that the entanglement may have an influence on the way that information is read off a strand of DNA and that it may be possible to exploit this experimentally. Just how, they don’t say.

Speculative but potentially explosive work.

Ref: arxiv.org/abs/1006.4053: The Relevance Of Continuous Variable Entanglement In DNA

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 and the Nature of Reality

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

O presente congela o passado?

Paper para ser lido e enviado ao Ion. A idéia de que o presente é análoga a um front de um processo de transição de fase (de uma fase super-resfriada?) é interessante. A onipresença de metáforas heurísticas na formulação de novas teorias científicas também é notável.
Update: Depois de ler o paper, acho que a idéia de um front de transição de fase ao longo do eixo temporal, bem como a analogia de que o sistema como um todo estaria em um estado “super-resfriado” (metaestável) poderiam ser melhor explorados.
Updade 2: Acho que o título do post deveria ter sido: “O passado congela o presente?”

Time and Spacetime: The Crystallizing Block Universe

(Submitted on 4 Dec 2009)

The nature of the future is completely different from the nature of the past. When quantum effects are significant, the future shows all the signs of quantum weirdness, including duality, uncertainty, and entanglement. With the passage of time, after the time-irreversible process of state-vector reduction has taken place, the past emerges, with the previous quantum uncertainty replaced by the classical certainty of definite particle identities and states. The present time is where this transition largely takes place, but the process does not take place uniformly: Evidence from delayed choice and related experiments shows that isolated patches of quantum indeterminacy remain, and that their transition from probability to certainty only takes place later. Thus, when quantum effects are significant, the picture of a classical Evolving Block Universe (`EBU’) cedes place to one of a Crystallizing Block Universe (`CBU’), which reflects this quantum transition from indeterminacy to certainty, while nevertheless resembling the EBU on large enough scales.

Comments: 25 Pages. 3 figures
Subjects: Quantum Physics (quant-ph); General Relativity and Quantum Cosmology (gr-qc)
Cite as: arXiv:0912.0808v1 [quant-ph]

Fotini, Fótons, Espaço e Tempo

Eu imagino que Fotini está acima dessas piadinhas machistas, de modo que reproduzo aqui. Estou lendo alguns de seus papers que estão no ArXiv (ver abaixo). Li o numero 2, sugerido peloo Ion Vasili Vancea, e gostei muito. Quem sabe daria para trabalhar em modelos de redes que, sofrendo uma transição de fase, geram a geometria da relatividade geral.

1. arXiv:0911.5075 [pdf, other]
A quantum Bose-Hubbard model with evolving graph as toy model for emergent spacetime
Comments: 23 pages, 6 figures; Typos corrected
Subjects: General Relativity and Quantum Cosmology (gr-qc); Strongly Correlated Electrons (cond-mat.str-el); High Energy Physics – Theory (hep-th); Quantum Physics (quant-ph)
2. arXiv:0909.1861 [pdf, other]
Space does not exist, so time can
Comments: Third prize of the FQXi ‘The Nature of Time’ Essay Contest
Subjects: General Relativity and Quantum Cosmology (gr-qc)
3. arXiv:0808.2495 [ps, pdf, other]
Lieb-Robinson bounds and the speed of light from topological order
Comments: 4 pages, 1 eps figure. Bound improved
Journal-ref: Phys.Rev.Lett.102:017204,2009
Subjects: Quantum Physics (quant-ph); Strongly Correlated Electrons (cond-mat.str-el); General Relativity and Quantum Cosmology (gr-qc); High Energy Physics – Lattice (hep-lat)
4. arXiv:0805.3175 [pdf, other]
Conserved Topological Defects in Non-Embedded Graphs in Quantum Gravity
Comments: 42 pages, 34 figures
Journal-ref: Class.Quant.Grav.25:205015,2008
Subjects: General Relativity and Quantum Cosmology (gr-qc)
5. arXiv:0801.0861 [ps, pdf, other]
Quantum Graphity: a model of emergent locality
Comments: 25 pages
Journal-ref: Phys.Rev.D77:104029,2008
Subjects: High Energy Physics – Theory (hep-th); General Relativity and Quantum Cosmology (gr-qc); Quantum Physics (quant-ph)
6. arXiv:gr-qc/0703097 [ps, pdf, other]
New directions in Background Independent Quantum Gravity
Comments: Comments 26 pages. Contribution to “Approaches to Quantum Gravity – toward a new understanding of space, time, and matter”, edited by D. Oriti, to be published by Cambridge University Press
Subjects: General Relativity and Quantum Cosmology (gr-qc)
7. arXiv:gr-qc/0703027 [ps, pdf, other]
Conserved Quantities in Background Independent Theories
Comments: 11 pages, 3 figures
Journal-ref: J.Phys.Conf.Ser.67:012019,2007
Subjects: General Relativity and Quantum Cosmology (gr-qc)
8. arXiv:gr-qc/0702044 [ps, pdf, other]
Disordered locality in loop quantum gravity states
Comments: 11 pages, 4 figures, revision with extended discussion of results
Journal-ref: Class.Quant.Grav.24:3813-3824,2007
Subjects: General Relativity and Quantum Cosmology (gr-qc)
9. arXiv:gr-qc/0601028 [ps, pdf, other]
Constrained Mechanics and Noiseless Subsystems
Comments: 15 pages
Subjects: General Relativity and Quantum Cosmology (gr-qc); Quantum Physics (quant-ph)
10. arXiv:gr-qc/0510052 [ps, pdf, other]
Geometry from quantum particles
Comments: 17 pages, LaTex
Subjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Physics – Theory (hep-th)
11. arXiv:hep-th/0505165 [ps, pdf, other]
A statistical formalism of Causal Dynamical Triangulations
Comments: 21 pages, 19 pictures, 1 graph, Published in section: Field Theory And Statistical Systems
Journal-ref: NPB 726 (2005) 494-509
Subjects: High Energy Physics – Theory (hep-th); Statistical Mechanics (cond-mat.stat-mech); General Relativity and Quantum Cosmology (gr-qc)
12. arXiv:hep-th/0409057 [ps, pdf, other]
Gauge fixing in Causal Dynamical Triangulations
Comments: 14 pages, 2 figures
Journal-ref: Nucl.Phys. B739 (2006) 120-130
Subjects: High Energy Physics – Theory (hep-th); General Relativity and Quantum Cosmology (gr-qc)
13. arXiv:hep-th/0409056 [ps, pdf, other]
Symmetry and entropy of black hole horizons
Comments: 17 pages, 1 figure, some criticisms of the result are answered
Journal-ref: Nucl.Phys. B744 (2006) 1-13
Subjects: High Energy Physics – Theory (hep-th); General Relativity and Quantum Cosmology (gr-qc)
14. arXiv:gr-qc/0311059 [ps, pdf, other]
Quantum Theory from Quantum Gravity
Comments: 17 pages, 2 eps figures
Journal-ref: Phys.Rev. D70 (2004) 124029
Subjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Physics – Theory (hep-th); Quantum Physics (quant-ph)
15. arXiv:hep-th/0302111 [ps, pdf, other]
Evolution in Quantum Causal Histories
Comments: 20 pages. 8 figures. (v3: minor corrections, additional references [2,3]) to appear in CQG
Journal-ref: Class.Quant.Grav. 20 (2003) 3839
Subjects: High Energy Physics – Theory (hep-th); General Relativity and Quantum Cosmology (gr-qc)
16. arXiv:gr-qc/0210086 [ps, pdf, other]
Planck-scale models of the Universe
Comments: 19 pages, 8 figures. Invited contribution to “Science & Ultimate Reality: From Quantum to Cosmos (Explorations Celebrating the Vision of John Archibald Wheeler)”. References added
Subjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Physics – Theory (hep-th)
17. arXiv:gr-qc/0203036 [ps, pdf, other]
Coarse graining in spin foam models
Comments: 38 pages, many eps figures
Journal-ref: Class.Quant.Grav. 20 (2003) 777-800
Subjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Physics – Theory (hep-th)
18. arXiv:hep-th/0006199 [ps, pdf, other]
An algebraic approach to coarse graining
Comments: Latex, 20 pages, 12 eps figures
Subjects: High Energy Physics – Theory (hep-th); Condensed Matter (cond-mat); General Relativity and Quantum Cosmology (gr-qc); High Energy Physics – Lattice (hep-lat)
19. arXiv:hep-th/9910146 [ps, pdf, other]
Holography in a quantum spacetime
Comments: 16 pages, LaTeX
Subjects: High Energy Physics – Theory (hep-th); General Relativity and Quantum Cosmology (gr-qc)
20. arXiv:hep-th/9904009 [ps, pdf, other]
Quantum causal histories
Comments: 16 pages, epsfig latex. Some clarifications, minor corrections and references added. Version to appear in Classical and Quantum Gravity
Journal-ref: Class.Quant.Grav. 17 (2000) 2059-2072
Subjects: High Energy Physics – Theory (hep-th); General Relativity and Quantum Cosmology (gr-qc)
21. arXiv:gr-qc/9811053 [ps, pdf, other]
The internal description of a causal set: What the universe looks like from the inside
Comments: Version to appear in Comm.Math.Phys. (minor modifications). 37 pages, several eps figures
Journal-ref: Commun.Math.Phys. 211 (2000) 559-583
Subjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Physics – Theory (hep-th)
22. arXiv:hep-th/9712148 [ps, pdf, other]
Nonperturbative dynamics for abstract (p,q) string networks
Comments: Latex, 12 pages, epsfig, 7 figures, minor changes
Journal-ref: Phys.Rev. D58 (1998) 084033
Subjects: High Energy Physics – Theory (hep-th); General Relativity and Quantum Cosmology (gr-qc)
23. arXiv:gr-qc/9712067 [ps, pdf, other]
Quantum geometry with intrinsic local causality
Comments: Latex 33 pages, 7 Figure, epsfig
Journal-ref: Phys.Rev. D58 (1998) 084032
Subjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Physics – Theory (hep-th)
24. arXiv:gr-qc/9704013 [ps, pdf, other]
Dual formulation of spin network evolution
Comments: Latex, 20 pages, 16 figures
Subjects: General Relativity and Quantum Cosmology (gr-qc)
25. arXiv:gr-qc/9702046 [ps, pdf, other]
4D diffeomorphisms in canonical gravity and abelian deformations
Comments: latex, 19 pages, 2 figures
Subjects: General Relativity and Quantum Cosmology (gr-qc)

Criticalidade e decoerência quântica

Este parece ser um paper importante. Para ler e estudar!

Critical dynamics of decoherence

(Submitted on 30 Nov 2009)

The quantum-classical border Niels Bohr postulated to account for the definiteness of measurement outcomes is explained by decoherence. Decoherence, as a destroyer of quantum coherence and entanglement, is also a respected foe in novel applications of quantum physics (such as quantum computing or quantum metrology). So far, studies of decoherence focused on systems prepared typically in a Schroedinger cat-like superposition, and then instantaneously coupled to an otherwise static environment. We study decoherence induced by many-body dynamic environment undergoing a non-equilibrium (quantum) phase transition. As environment “monitors” the quantum system, its sensitivity — and, consequently, efficiency of decoherence — is amplified by a phase transition, as is often the case in the real world detectors (bubble chambers, photographic emulsions, or rhodopsin in our eyes). We show that decoherence happens almost exclusively as the critical point of the environment is traversed, and is significantly enhanced by its non-equilibrium phase transition dynamics. Our calculation yields a simple expression that relates decoherence to the universal critical exponents in a way that parallels theory of topological defect creation in non-equilibrium phase transitions.

Comments: 5+5 pages, 4 figures, comments are welcome !
Subjects: Quantum Physics (quant-ph); Statistical Mechanics (cond-mat.stat-mech); High Energy Physics – Theory (hep-th)
Report number: LA-UR 09-06655
Cite as: arXiv:0911.5729v1 [quant-ph]

Apenas três axiomas para obter a teoria quântica?

Quantum Theory and Beyond: Is Entanglement Special?

Borivoje Dakic, Caslav Brukner
(Submitted on 3 Nov 2009)

Quantum theory makes the most accurate empirical predictions and yet it lacks simple, comprehensible physical principles from which the theory can be uniquely derived. A broad class of probabilistic theories exist which all share some features with quantum theory, such as probabilistic predictions for individual outcomes (indeterminism), the impossibility of information transfer faster than speed of light (no-signaling) or the impossibility of copying of unknown states (no-cloning). A vast majority of attempts to find physical principles behind quantum theory either fall short of deriving the theory uniquely from the principles or are based on abstract mathematical assumptions that require themselves a more conclusive physical motivation. Here, we show that classical probability theory and quantum theory can be reconstructed from three reasonable axioms: (1) (Information capacity) All systems with information carrying capacity of one bit are equivalent. (2) (Locality) The state of a composite system is completely determined by measurements on its subsystems. (3) (Reversibility) Between any two pure states there exists a reversible transformation. If one requires the transformation from the last axiom to be continuous, one separates quantum theory from the classical probabilistic one. A remarkable result following from our reconstruction is that no probability theory other than quantum theory can exhibit entanglement without contradicting one or more axioms.

Comments: 14 pages, 4 figures
Subjects: Quantum Physics (quant-ph)
Cite as: arXiv:0911.0695v1 [quant-ph]

Avalanches com memória?

A estadia na casa do Ion rendeu. Além dos dois seminários, e de eu poder divulgar o concurso para Prof. Dr. em Física Estatística e Física Matemática que está aberto no DFM-FFCLRP-USP (nota: preciso avisar o Vitor Leite Barbanti!), pudemos conversar bastante sobre física.
Minha cultura sobre a teoria de supercordas aumentou (um pouco!), minha admiração por Lee Smolin diminuiu (um pouco! – Ion disse simplesmente: mas que problema de física ou matemática Smolin resolveu mesmo? Não me lembro…), e agendamos uma contribuição para um livro de Mecânica Quântica baseado em pequenos textos e muitos problemas resolvidos.
Não gostei muito do abstract deste paper, mas a idéia tem (talvez) a ver com que o discuti ontem com o Ion: agora que as avalanches neuronais estão bem estabelecidas, fica a questão de sua relação com o código neural (mas será que neurônios realmente tem um código? Ou tudo é um sistema dinâmico parcialmente isolado que iterage com o mundo (outro sistema dinâmico). Será que vale a pena retomar aquela idéia do Plenz de que, via mecanismo Hebbianos, as avalanches vão sendo gravadas pouco a pouco nas redes, formando avalanches preferenciais (processos de ramificação com memória nos p_{ij}?) A ponderar…
PS: Será que já inventaram um editor de Latex decente para o Blogger? Será que vale a pena migrar par o WordPress?

Learning sculpts the spontaneous activity of the resting human brain

É um PNAS, talvez valha a pena ler… Mas o abstract está bem fraquinho…

Por que existem fermions?


A resposta fácil é que, se existissem apenas bósons, nós não estaríamos aqui para fazer a pergunta… Eu sempre tive a curiosidade de saber se o Princípio de Pauli pode ser deduzido de uma teoria mais profunda ou é um fato empírico sem justificativa teórica. Falar sobre funções de onda anti-simétricas para fermions não é uma explicação, mas apenas uma reformulação tautológica do princípio…

Experimental test of the Pauli Exclusion Principle

A.S. Barabash
(Submitted on 26 Aug 2009)

A short review is given of three experimental works on tests of the Pauli Exclusion Principle (PEP) in which the author has been involved during the last 10 years. In the first work a search for anomalous carbon atoms was done and a limit on the existence of such atoms was determined, $^{12}\tilde{\mathrm C}$ / $^{12}$C $<>

Comments: 19 pages, 9 figures; talk at Workshop “Theoretical and experimental aspects on the spin-statistics connection and related symmetries” (Trieste, Italy, October 21-25, 2008)
Subjects: High Energy Physics – Experiment (hep-ex); Nuclear Experiment (nucl-ex)
Cite as: arXiv:0908.3795v1 [hep-ex]

No princípio era o Bit

Do Physics ArXiv Blog, com tradução não editada do Tradutor Google (estou testando o mesmo):

The foundation of reality: information or quantum mechanics?

Posted: 17 May 2009 09:10 PM PDT

The nature of information is the key question for those pondering the laws of physics

We’ve all come across the mind-blowing weirdness of quantum mechanics; that it makes its predictions in probabilistic rather them deterministic form, that it does not allow unknown states to be copied and that one quantum object can instantly influence another regardless of the distance between them, but not in a way that allows faster-than-light communication.

That’s one helluva a theory and in recent years physicists have discovered an entire class of theories that do the same kind of thing. The question is which one do we choose? 

A few can be ruled out because they simplify various computational tasks in implausible ways. But the rest have seemed more or less equivalent. Until now.

Marcin Pawlowski at the University of Gdansk in Poland and a few pals say that the addition of a single additional consideration, quickly and easily separates the non-physical theories from the physical ones.

The idea is based around information and can be stated simply. The rule is this: the sending of “m” classical bits causes an information gain of, at most, “m” bits. 

It sounds bewilderingly simple and perhaps it is. Pawlowski and co say that without this principle, non-physical theories allow extra information to be sent. They point out that the rule applies only to classical bits. In the real quantum world, extra infromation can be sent using the ideas of super dense coding.

The team say because the idea distinguishes between physical and non-physical versions of quantum mechanics, it must be a fundamental property of the universe.

Perhaps. The problem with this argument is that the new rule so far gives no insight into the nature of quantum mechanics (or information) and seems to have no predictive power. That’s not going to be much use to anybody. 

The truth is that this team is not the first to consider the role that information plays in quantum mechanics. 

There are no shortage of theorists who recognise the problem of understanding the nature of information as the outstanding mystery of our era. 

Various teams are wrestling with the problem of producing a quantum version of Shannon’s Theory of Communication which describes how a classical message created at one point in space can be recreated at another. The problem is how to describe in very general terms the rules that govern how a quantum message created at one point in space can be recreated at another.

Others are attempting to redraw the laws of quantum mechanics in terms of quantum information alone. 

Roy Frieden at the University of Arizon in Phoenix, has already derived the laws of physics, including the Schrodinger equation, using the powerful idea of Fisher information (although the method has not produced the kind of predictions needed to make it mainstream). 

All this work stems from the growing realisation that it is not the laws of physics that determine how information behaves in our Universe, but the other way round. The implication is extraordinary: that somehow, information is the ghostly bedrock of our Universe and from it, all else is derived. That really is mind-blowing.

Ref: arxiv.org/abs/0905.2292: A New Physical Principle: Information Causality

Nós todos entrar em toda a mente-blowing weirdness da mecânica quântica, que faz a sua previsão probabilística, em vez deles deterministic forma, que não permitem desconhecido para ser copiado e afirma que um objeto quântico pode influenciar outra instantaneamente, independentemente da distância entre eles, mas não de uma forma que permita que mais rápido do que luz comunicação. 
Isso é um helluva uma teoria e, nos últimos anos físicos já descobriram uma classe inteira de teorias que fazer o mesmo tipo de coisa. A questão é que temos uma escolha? 
Alguns podem ser excluída porque simplificam diversas tarefas computacionais em implausível maneiras. Mas o resto parecia ter mais ou menos equivalentes. Até agora. 
Marcin Pawlowski, da Universidade de Gdansk, na Polónia e alguns amigos dizem que a adição de uma única consideração adicional, de forma rápida e fácil separa os não-físicos teorias da física queridos. 
A ideia baseia-se em torno de informações e pode ser simplesmente declarou. A regra é esta: o envio de “m” clássica bits provoca um ganho de informação, no máximo, “m” bits. 
Parece bewilderingly simples e talvez seja. Pawlowski e co dizer que sem este princípio, não são teorias físicas permitem informação extra para ser enviado. Eles apontam que a regra se aplica apenas aos clássicos bits. No mundo real quântica, extra infromation podem ser enviadas através das idéias de super densa codificação. 
A equipe diz, porque a ideia de uma distinção entre físico e não físico versões da mecânica quântica, esta deve ser uma propriedade fundamental do universo. 
Talvez. O problema com este argumento é que a nova regra até agora não dá insight sobre a natureza da mecânica quântica (ou informação) e parece não ter qualquer poder preditivo. Isso não vai ter muita utilidade para ninguém. 
A verdade é que esta equipa não é o primeiro a analisar o papel que a informação desempenha na mecânica quântica. 
Não há escassez de teóricos que reconhecer o problema de compreensão da natureza das informações que o mistério de nossa era notável. 
Várias equipes estão lutando com o problema de produzir uma versão quântica de Shannon da Teoria da Comunicação, que descreve como uma clássica mensagem criada em um ponto no espaço pode ser recriado em outra. O problema é a forma de descrever em termos muito gerais, as regras que regem a forma como um quantum mensagem criada em um ponto no espaço pode ser recriado em outra. 
Outros estão a tentar redesenhar as leis da mecânica quântica em termos de informação quântica sozinho. 
Roy Frieden da Universidade de Arizon em Phoenix, já derivadas as leis da física, incluindo o Schrodinger equação, utilizando a poderosa idéia de Fisher informação (embora o método não produziu o tipo de previsões necessárias para tornar mainstream). 
Todo este trabalho decorre da crescente realização que não é as leis da física que determinam como a informação comporta em nosso Universo, mas em sentido inverso. A implicação é extraordinária: de que, de alguma, a informação é o alicerce espiritual de nosso universo e com ela, tudo é derivado. Isso realmente é mind-blowing. 
Ref: arxiv.org/abs/0905.2292: um novo princípio físico: Informação Causalidade

Ilusões quânticas ou quânticos iludidos?


Ainda do physics Arxiv Blog:

Quantum consciousness, a phrase that sends most eggheads running for the hills, is currently on a roll. A coupla months back, Efstratios “Moussaka” Manousakis of Florida State University in Tallahassee published a paper suggesting that a certain kinda optical illusion could be explained in quantum terms.

The optical illusion in question is the double image flip like the one above which switches from one scene to another in the viewer’s mind. Neuroscientists have always wondered why ya can’t see both images at the same time.

The new thinkin is that the image exists in a kinda quantum superposition of both states. When this state collapses, it gives the observer the sense that he or she is lookin at one scene or the other (but not both). That sounds interesting but the impressive thing about Moussaka’s work is that it succesfully predicts the rate at which this flipping occurs in humans.

Now quantum physicist Henry “Goose” Stapp from the Lawerence Berkeley National Lab in Berkeley has entered the fray. His contribution is to tackle some of the criticism that has been levelled at Moussaka’s idea, in particular, the charge that in our warm, wet brains, decoherence destroys any quantum effects before they even get going.

Not so says Stapp. He argues that there exists a kinda twilight zone in which quantum phenomena can follow classical trajectories without being influenced by decoherence. So the collapse that triggers the conscious observation of one image or the other is essentially a classical phenomena that is steered by a few key quantum rules. It is therefore immune to decoherence.

Interesting idea but you can almost hear neuroscientists sucking their teeth as they read it. Stapp’s gonna need some more evidence and lots of it before an idea like this can become mainstream.

Ref: arxiv.org/abs/0710.5569: The Quantum-Classical and Mind-Brain Linkages: The Quantum Zeno Effect in Binocular Rivalry

Para modelos com redes neurais clássicas, ver aqui no Arxiv ou no Physica D se você tem assinatura:

Lá eu explico ilusões com multiestabilidade (mais de 10 imagens coexistindo, ver abaixo) com uma frequência acelerada em relação à biestabilidade clássica (cubo de Necker). Não acho que as idéias de Manousakis possam fazer isso…