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Multiverso e Ajuste Fino: o que ler?

mUltiverseCut and paste do ótimo post de Luke Barnes: 

What to Read: The Fine-Tuning of the Universe for Intelligent life

I’ve spent a lot of time critiquing articles on the fine-tuning of the universe for intelligent life. I should really give the other side of the story. Below are some of the good ones, ranging from popular level books to technical articles. I’ve given my recommendations for popular cosmology books here.

Books – Popular-level

  • Just Six Numbers, Martin Rees – Highly recommended, with a strong focus on cosmology and astrophysics, as you’d expect from the Astronomer Royal. Rees gives a clear exposition of modern cosmology, including inflation, and ends up giving a cogent defence of the multiverse.
  • The Goldilocks Enigma, Paul Davies – Davies is an excellent writer and has long been an important contributor to this field. His discussion of the physics is very good, and includes a description of the Higgs mechanism. When he strays into metaphysics, he is thorough and thoughtful, even when he is defending conclusions that I don’t agree with.
  • The Cosmic Landscape: String Theory and the Illusion of Intelligent Design, Leonard Susskind – I’ve reviewed this book in detail in a previous blog posts. Highly recommended. I can also recommend his many lectures on YouTube.
  • Constants of Nature, John Barrow – A discussion of the physics behind the constants of nature. An excellent presentation of modern physics, cosmology and their relationship to mathematics, which includes a chapter on the anthropic principle and a discussion of the multiverse.
  • Cosmology: The Science of the Universe, Edward Harrison – My favouritecosmology introduction. The entire book is worth reading, not least the sections on life in the universe and the multiverse.
  • At Home in the Universe, John Wheeler – A thoughtful and wonderfully written collection of essays, some of which touch on matters anthropic.

I haven’t read Brian Greene’s book on the multiverse but I’ve read his other books and they’re excellent. Stephen Hawking discusses fine-tuning in A Brief History of Time and the Grand Design. As usual, read anything by Sean Carroll, Frank Wilczek, and Alex Vilenkin.

Books – Advanced

  • The Cosmological Anthropic Principle, Barrow and Tipler – still the standard in the field. Even if you can’t follow the equations in the middle chapters, it’s still worth a read as the discussion is quite clear. Gets a bit speculative in the final chapters, but its fairly obvious where to apply your grain of salt.
  • Universe or Multiverse (Edited by Bernard Carr) – the new standard. A great collection of papers by most of the experts in the field. Special mention goes to the papers by Weinberg, Wilczek, Aguirre, and Hogan.

Scientific Review Articles

The field of fine-tuning grew out of the so-called “Large numbers hypothesis” of Paul Dirac, which is owes a lot to Weyl and is further discussed by Eddington, Gamow and others. These discussions evolve into fine-tuning when Dicke explains them using the anthropic principle. Dicke’s method is examined and expanded in these classic papers of the field:

A number of papers, while not discussing fine-tuning, are very relevant as they discuss how the macroscopic universe depends on the values of fundamental constants. Here are a few good examples.

Here are a few good review papers, arranged in order of increasing technical level.

Technical scientific articles

Here are some of the papers that have performed detailed calculations of specific fine-tuning cases, in chronological order.

Particle Physics Parameters

Cosmology Parameters

Philosophical articles and books

  • Issues in the Philosophy of Cosmology, Ellis (2006). An excellent review of some of the philosophical issues raised by modern cosmology, including fine-tuning. See also “Philosophy of Cosmology” by Chris Smeenk.
  • Universes, John Leslie – A tremendously clear exposition of what conclusions we can and should draw from fine tuning. Leslie loves a good analogy, and his choice of illustration is almost always excellent. Another must read.

Part of the reason why the fine-tuning of the universe for life is of such interest to philosophers is that it is often used as a premise in an argument for the existence of God.  A lot of the literature on the fine-tuning argument, pro and con, misses the mark by a large margin, in my opinion. Here are three of the best expositions of this argument.

Unsurprisingly, such claims have not gone unchallenged. Here are some of the best responses.

  • Does the Universe Need God?, Sean Carroll (2012) – A good, if brief, response to the arguments above. I recently presented fine-tuning with Carroll in the audience and he gave some good comments. I wouldn’t mind seeing him give an extended response.
  • See also the books by Leonard Susskind and Alex Vilenkin (and, though I haven’t read them, Brian Greene and Stephen Hawking) for a defence of the multiverse as the correct explanation for fine-tuning.
  • Probabilities and the Fine‐Tuning Argument: a Sceptical View, McGrew, McGrew and Vestrup – A critique of the fine-tuning argument for the existence of God based on skepticism as to the applicability of probabilities to hypothetical universes. At least two of the authors are theists. See also this paper by Bradley Monton (though I don’t think that the “old evidence” problem exists for Bayesian theories of probability.)

Read more [+]

Nosso universo vai congelar como uma cerveja super-resfriada…


Finding the Higgs? Good news. Finding its mass? Not so good.

“Fireballs of doom” from a quantum phase change would wipe out present Universe.

by  – Feb 19 2013, 8:55pm HB

A collision in the LHC’s CMS detector.

Ohio State’s Christopher Hill joked he was showing scenes of an impending i-Product launch, and it was easy to believe him: young people were setting up mats in a hallway, ready to spend the night to secure a space in line for the big reveal. Except the date was July 3 and the location was CERN—where the discovery of the Higgs boson would be announced the next day.

It’s clear the LHC worked as intended and has definitively identified a Higgs-like particle. Hill put the chance of the ATLAS detector having registered a statistical fluke at less than 10-11, and he noted that wasn’t even considering the data generated by its partner, the CMS detector. But is it really the one-and-only Higgs and, if so, what does that mean? Hill was part of a panel that discussed those questions at the meeting of the American Association for the Advancement of Science.

As theorist Joe Lykken of Fermilab pointed out, the answers matter. If current results hold up, they indicate the Universe is currently inhabiting what’s called a false quantum vacuum. If it were ever to reach the real one, its existing structures (including us), would go away in what Lykken called “fireballs of doom.”

We’ll look at the less depressing stuff first, shall we?

Zeroing in on the Higgs

Thanks to the Standard Model, we were able to make some very specific predictions about the Higgs. These include the frequency with which it will decay via different pathways: two gamma-rays, two Z bosons (which further decay to four muons), etc. We can also predict the frequency of similar looking events that would occur if there were no Higgs. We can then scan each of the decay pathways (called channels), looking for energies where there is an excess of events, or bump. Bumps have shown up in several channels in roughly the same place in both CMS and ATLAS, which is why we know there’s a new particle.

But we still don’t know precisely what particle it is. The Standard Model Higgs should have a couple of properties: it should be scalar and should have a spin of zero. According to Hill, the new particle is almost certainly scalar; he showed a graph where the alternative, pseudoscalar, was nearly ruled out. Right now, spin is less clearly defined. It’s likely to be zero, but we haven’t yet ruled out a spin of two. So far, so Higgs-like.

The Higgs is the particle form of a quantum field that pervades our Universe (it’s a single quantum of the field), providing other particles with mass. In order to do that, its interactions with other particles vary—particles are heavier if they have stronger interactions with the Higgs. So, teams at CERN are sifting through the LHC data, checking for the strengths of these interactions. So far, with a few exceptions, the new particle is acting like the Higgs, although the error bars on these measurements are rather large.

As we said above, the Higgs is detected in a number of channels and each of them produces an independent estimate of its mass (along with an estimated error). As of the data Hill showed, not all of these estimates had converged on the same value, although they were all consistent within the given errors. These can also be combined mathematically for a single estimate, with each of the two detectors producing a value. So far, these overall estimates are quite close: CMS has the particle at 125.8GeV, Atlas at 125.2GeV. Again, the error bars on these values overlap.

Oops, there goes the Universe

That specific mass may seem fairly trivial—if it were 130GeV, would you care? Lykken made the argument you probably should. But he took some time to build to that.

Lykken pointed out, as the measurements mentioned above get more precise, we may find the Higgs isn’t decaying at precisely the rates we expect it to. This may be because we have some details of the Standard Model wrong. Or, it could be a sign the Higgs is also decaying into some particles we don’t know about—particles that are dark matter candidates would be a prime choice. The behavior of the Higgs might also provide some indication of why there’s such a large excess of matter in the Universe.

But much of Lykken’s talk focused on the mass. As we mentioned above, the Higgs field pervades the entire Universe; the vacuum of space is filled with it. And, with a value for the Higgs mass, we can start looking into the properties of the Higgs filed and thus the vacuum itself. “When we do this calculation,” Lykken said, “we get a nasty surprise.”

It turns out we’re not living in a stable vacuum. Eventually, the Universe will reach a point where the contents of the vacuum are the lowest energy possible, which means it will reach the most stable state possible. The mass of the Higgs tells us we’re not there yet, but are stuck in a metastable state at a somewhat higher energy. That means the Universe will be looking for an excuse to undergo a phase transition and enter the lower state.

What would that transition look like? In Lykken’s words, again, “fireballs of doom will form spontaneously and destroy the Universe.” Since the change would alter the very fabric of the Universe, anything embedded in that fabric—galaxies, planets, us—would be trashed during the transition. When an audience member asked “Are the fireballs of doom like ice-9?” Lykken replied, “They’re even worse than that.”

Lykken offered a couple of reasons for hope. He noted the outcome of these calculations is extremely sensitive to the values involved. Simply shifting the top quark’s mass by two percent to a value that’s still within the error bars of most measurements, would make for a far more stable Universe.

And then there’s supersymmetry. The news for supersymmetry out of the LHC has generally been negative, as various models with low-mass particles have been ruled out by the existing data (we’ll have more on that shortly). But supersymmetry actually predicts five Higgs particles. (Lykken noted this by showing a slide with five different photos of Higgs taken at various points in his career, in which he was “differing in mass and other properties, as happens to all of us.”) So, when the LHC starts up at higher energies in a couple of years, we’ll actually be looking for additional, heavier versions of the Higgs.

If those are found, then the destruction of our Universe would be permanently put on hold. “If you don’t like that fate of the Universe,” Lykken said, “root for supersymmetry”

Planetas extra-solares, Kepler 62 e o Paradoxo de Fermi local

Conforme aumentam o número de planetas extra-solares descobertos, também aumentamos vínculos sobre as previsões do modelo de percolação galática (Paradoxo de Fermi Local).
A previsão é que, se assumirmos que Biosferas Meméticas (Biosferas culturais ou Tecnosferas) são um resultado provável de Biosferas Genéticas, então devemos estar dentro de uma região com pucos planetas habitáveis. Pois se existirem planetas habitados (por seres inteligentes) por perto, com grande probabilidade eles são bem mais avançados do que nós, e já teriam nos colonizado.
Como isso ainda não ocorreu (a menos que se acredite nas teorias de conspiração dos ufólogos e nas teorias de Jesus ET, deuses astronautas etc.), segue que quanto mais os astronomos obtiverem dados, mais ficará evidente que nosso sistema solar é uma anomalia dentro de nossa vizinhança cósmica (1000 anos-luz?), ou seja, não podemos assumir o Princípio Copernicano em relação ao sistema solar: nosso sistema solar não é tipico em nossa vizinhança.  Bom, pelo menos, essa conclusão está batendo com os dados coletados até hoje…
Assim, é possível fazer a previsão de que uma maior análise dos planetas Kepler 62-e e Kepler 62-f revelará que eles não possuem uma atmosfera com oxigênio ou metano, sinais de um planeta com biosfera.

Persistence solves Fermi Paradox but challenges SETI projects

Osame Kinouchi (DFM-FFCLRP-Usp)
(Submitted on 8 Dec 2001)

Persistence phenomena in colonization processes could explain the negative results of SETI search preserving the possibility of a galactic civilization. However, persistence phenomena also indicates that search of technological civilizations in stars in the neighbourhood of Sun is a misdirected SETI strategy. This last conclusion is also suggested by a weaker form of the Fermi paradox. A simple model of a branching colonization which includes emergence, decay and branching of civilizations is proposed. The model could also be used in the context of ant nests diffusion.

03/05/2013 – 03h10

Possibilidade de vida não se resume a planetas similares à Terra, diz estudo


Com as diferentes composições, massas e órbitas possíveis para os planetas fora do Sistema Solar, a vida talvez não esteja limitada a mundos similares à Terra em órbitas equivalentes à terrestre.

Editoria de arte/Folhapress

Essa é uma das conclusões apresentada por Sara Seager, do MIT (Instituto de Tecnologia de Massachusetts), nos EUA, em artigo de revisão publicado no periódico “Science“, com base na análise estatística dos cerca de 900 mundos já detectados ao redor de mais de 400 estrelas.

Seager destaca a possível existência de planetas cuja atmosfera seria tão densa a ponto de preservar água líquida na superfície mesmo a temperaturas bem mais baixas que a terrestre. 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

Seleção Artificial Cosmológica: primeiras referências

Tive a mesma ideia em 1995, mas não publiquei. Sexta feira passada, achei numa pasta abandonada os escritos que estão digitalizados aqui.  Por um erro de memória, confundi Lee Smolin (em inglês e mais completo aqui) com Sidney Coleman.

Meduso-anthropic principle

The meduso-anthropic principle is a quasi-organic universe theory originally proposed by mathematician and quantum gravity scholar Louis Crane in 1994.



Universes and black holes as potential life cycle partners

Crane’s MAP is a variant of the hypothesis of cosmological natural selection (fecund universes), originally proposed by cosmologist Lee Smolin (1992). It is perhaps the first published hypothesis of cosmological natural selection with intelligence (CNS-I), where intelligence plays some proposed functional role in universe reproduction. It is also an interpretation of the anthropic principle (fine-tuning problem). The MAP suggests the development and life cycle of the universe is similar to that of Corals and Jellyfish, in which dynamic Medusa are analogs for universal intelligence, in co-evolution and co-development with sessile Polyp generations, which are analogs for both black-holes and universes. In the proposed life cycle, the Universe develops intelligent life and intelligent life produces new baby universes. Crane further speculates that our universe may also exist as a black hole in a parallel universe, and extraterrestrial life there may have created that black hole.

Crane’s work was published in 1994 as a preprint on arXiv.org. In 1995, in an an article in QJRAS, emeritus cosmologist Edward Harrison (1919-2007) independently proposed that the purpose of intelligent life is to produce successor universes, in a process driven by natural selection at the universal scale. Harrison’s work was apparently the first CNS-I hypothesis to be published in a peer-reviewed journal.

Why future civilizations might create black holes

Crane speculates that successful industrial civilizations will eventually create black holes, perhaps for scientific research, for energy production, or for waste disposal. After the hydrogen of the universe is exhausted civilizations may need to create black holes in order to survive and give their descendants the chance to survive. He proposes that Hawking radiation from very small, carefully engineered black holes would provide the energy enabling civilizations to continue living when other sources are exhausted.

Philosophical implications

According to Crane, Harrison, and other proponents of CNS-I, mind and matter are linked in an organic-like paradigm applied at the universe scale. Natural selection in living systems has given organisms the imperative to survive and reproduce, and directed their intelligence to that purpose. Crane’s MAP proposes a functional purpose for intelligence with respect to universe maintenance and reproduction. Universes of matter produce intelligence, and intelligent entities are ultimately driven to produce new universes.

See also


Os deuses de Richard Dawkins

File:NASA child bubble exploration.jpgMy personal theology is described in the Gifford lectures that I gave at Aberdeen in Scotland in 1985, published under the title, Infinite In All Directions. Here is a brief summary of my thinking. The universe shows evidence of the operations of mind on three levels. The first level is elementary physical processes, as we see them when we study atoms in the laboratory. The second level is our direct human experience of our own consciousness. The third level is the universe as a whole. Atoms in the laboratory are weird stuff, behaving like active agents rather than inert substances. They make unpredictable choices between alternative possibilities according to the laws of quantum mechanics. It appears that mind, as manifested by the capacity to make choices, is to some extent inherent in every atom. The universe as a whole is also weird, with laws of nature that make it hospitable to the growth of mind. I do not make any clear distinction between mind and God. God is what mind becomes when it has passed beyond the scale of our comprehension. God may be either a world-soul or a collection of world-souls. So I am thinking that atoms and humans and God may have minds that differ in degree but not in kind. We stand, in a manner of speaking, midway between the unpredictability of atoms and the unpredictability of God. Atoms are small pieces of our mental apparatus, and we are small pieces of God’s mental apparatus. Our minds may receive inputs equally from atoms and from God. This view of our place in the cosmos may not be true, but it is compatible with the active nature of atoms as revealed in the experiments of modern physics. I don’t say that this personal theology is supported or proved by scientific evidence. I only say that it is consistent with scientific evidence.  Freeman Dyson

Parece que Dawkins está rumando para uma posição similar à de Gardner, Clément Vidal e outros da comunidade Evo-Devo Universe.

Human Gods

After two hours of conversation, Professor Dawkins walks far afield. He talks of the possibility that we might co-evolve with computers, a silicon destiny. And he’s intrigued by the playful, even soul-stirring writings of Freeman Dyson, the theoretical physicist.

In one essay, Professor Dyson casts millions of speculative years into the future. Our galaxy is dying and humans have evolved into something like bolts of superpowerful intelligent and moral energy.

Doesn’t that description sound an awful lot like God?

“Certainly,” Professor Dawkins replies. “It’s highly plausible that in the universe there are God-like creatures.”

He raises his hand, just in case a reader thinks he’s gone around a religious bend. “It’s very important to understand that these Gods came into being by an explicable scientific progression of incremental evolution.”

Could they be immortal? The professor shrugs.

“Probably not.” He smiles and adds, “But I wouldn’t want to be too dogmatic about that.”

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

O (quase) primeiro post do SEMCIÊNCIA

Estou fazendo a importação do SEMCIÊCIA do Blogger para o WordPress (não sabia que era tão fácil). Topei com este primeiro post, de 19 de junho de 2006. Infelizmente existe um gap nos posts antigos (os posts de maio, mês de nascimento do blog, e os posts de junho a dezembro (mais de 200!) foram deletados porque… hummm, naquela época eu estava me preparando para um concurso de livre docência e algumas pessoas diziam que ter um blog não era algo sério e que poderia me prejudicar se eu emitisse opiniões politicamente incorretas (em relação à USP), por exemplo. Ou seja, este não é realmente o primeiro post, mas sim, o primeiro que sobreviveu…

Mas este post de junho sobrou eu algum lugar, em um cache que achei um ano depois, e foi recuperado. Estou reproduzindo o mesmo porque o acho ainda bem atual e, além disso, pelo fato de que finalmente irei ministrar pela segunda vez a disciplina a que ele se refere, para a turma de Licenciatura em Química da FFCLRP.




Coincidência de novo. Eu estava aqui procurando uma figura para fazer este post sobre o volume especial “As diferentes faces do infinito” quando recebi um e-mail da Ana Cláudia Ferrari me dizendo que, sim, eu havia ganho duas assinaturas de graça, da SciAm e da Viver Mente e Cérebro. Tão vendo? Quem disse que não ganho nada com este blog?

É claro que isso não vai afetar minha atitude quanto à revista, pois a compro desde o primeiro número. Afinal basta eles manterem a qualidade e ocuparem o nicho da SUPERINTERESSANTE (pois esta está querendo substituir a PLANETA, que por sua vez trocou o esoterismo pela ecologia) já está ótimo! Todo apoio a você, SciAm!

A Ana me perguntou se é verdade que meus alunos realmente lêem as revistas. Bom, alunos de Estatística I, respondam prá ela ai nos comentários. Em todo caso, conto aqui duas maneiras de usar a SciAm nas salas de aula que já testei.

Bom, primeiro eu sou responsável por uma disciplina optativa do Departamento de Química aqui na FFCLRP chamada Tópicos de Ciência Contemporânea, cuja ementa está meio ambiciosa, concordo:


Introduzir e incentivar o estudante a ter contato com a literatura científica e de divulgação científica, traçando um panorama da ciência contemporânea que permita uma visão contextualizada e crítica de diferentes áreas do conhecimento tais como a Cosmologia, a Física, a Química e a Biologia. Read more [+]

Uma prova matemática de que o Universo teve um início?

Mathematics of Eternity Prove The Universe Must Have Had A Beginning — Part II

Heavyweight cosmologists are battling it out over whether the universe had a beginning. And despite appearances, they may actually agree



Friday, April 27, 2012

Earlier this week, Audrey Mithani and Alexander Vilenkin at Tufts University in Massachusetts argued that the mathematical properties of eternity prove that the universe must have had a beginning.

Today, another heavyweight from the world of cosmology weighs in with an additional argument. Leonard Susskind at Stanford University in California, says that even if the universe had a beginning, it can be thought of as eternal for all practical purposes.

Susskind is good enough to give a semi-popular version of his argument:

“To make the point simply, imagine Hilbertville, a one-dimensional semi-infinite city, whose border is at x = 0: The population is infinite and uniformly fills the positive axis x > 0: Each citizen has an identical telescope with a finite power. Each wants to know if there is a boundary to the city. It is obvious that only a finite number of citizens can see the boundary at x = 0. For the infinite majority the city might just as well extend to the infinite negative axis.

Thus, assuming he is typical, a citizen who has not yet studied the situation should bet with great confidence that he cannot detect a boundary. This conclusion is independent of the power of the telescopes as long as it is finite.”

He goes on to discuss various thermodynamic arguments that suggest the universe cannot have existed for ever. The bottom line is that the inevitable increase of entropy over time ensures that a past eternal universe ought to have long since lost any semblance of order. Since we can see order all around us, the universe cannot be eternal in the past.

He finishes with this: “We may conclude that there is a beginning, but in any kind of inflating cosmology the odds strongly (infinitely) favor the beginning to be so far in the past that it is eff ectively at minus infinity.”

Susskind is a big hitter: a founder of string theory and one of the most influential thinkers in this area. However, it’s hard to agree with his statement that this argument represents the opposing view to Mithani and Vilenkin’s.

His argument is equivalent to saying that the cosmos must have had a beginning even if it looks eternal in the past, which is rather similar to Mithani and Vilenkin’s view. The distinction that Susskind does make is that his focus is purely on the practical implications of this–although what he means by ‘practical’ isn’t clear.

That the universe did or did not have a beginning is profoundly important from a philosophical point of view, so much so that a definitive answer may well have practical implications for humanity.

But perhaps the real significance of this debate lies elsewhere. The need to disagree in the face of imminent agreement probably tells us more about the nature of cosmologists than about the cosmos itself.

Ref: arxiv.org/abs/1204.5385: Was There a Beginning?

Estamos em um período revolucionário na Física? Neutrinos anômalos, anti-mesons anômalos e Multiverso como ortodoxia

Achei um blog muito bom para seguir o desdobramento da controvérsia sobre os neutrinos aparentemente superluminais:

Of Particular Significance

Conversations About Science with Theoretical Physicist Matt Strassler

Cientistas famosos como Lee Smolin comentam neste blog. Acho que vou começar a seguir o caso dos neutrinos apenas por este blog e evitar as notícias de jornal e de revistas de divulgação. O blog também comenta sobre as tentativas de explicaçãoda anomalia que estão saindo no ArXiv. O status atual, segundo Matt, é que mesmo o paper do ICARUS e o paper de CG não constituem uma refutação dos resultados do OPERA, pois usam pressupostos teóricos que podem estar errados caso a relação de dispersão dos neutrinos seja outra que a da relatividade restrita. E, ao contrário de Jorge Stolfi, Matt não acredita que o problema com o OPERA tem a ver com as medidas de distância e tempo.

Neutrinos and multiverses: a new cosmology beckons

You wait decades for discoveries that could revolutionise physics, then three come along at once

“THE universe is not only queerer than we suppose, but queerer than we can suppose,” as geneticist J. B. S. Haldane once remarked. In recent decades, physicists have done their best to prove Haldane wrong, by supposing some very queer universes indeed.

Their speculations may seem fantastical, but they are well motivated. Physics poses some formidable questions that we are so far unable to answer. Why is the universe dominated by matter not antimatter? Why does our universe appear to be “fine-tuned” with just the right properties to give rise to galaxies, stars, planets, life and physicists?

The existing edifice of physics, built upon the twin foundations of general relativity and quantum mechanics, is clearly in need of renovation. We have been waiting for years for cracks to appear that might tell us how to go about it. But up to now, nature has remained stubbornly unmoved.

In the past few weeks, however, promising cracks have opened up. In September came stunning news of neutrinos travelling faster than the speed of light. Sceptics withheld judgement but now a new analysis has affirmed the initial result (see “More data shows neutrinos still faster than light”). We still await independent verification – doubts have already been cast – but if it holds up the implications are enormous, opening the door to a new and very different picture of the cosmos.

No less tantalising is a report that particles called mesons decay differently from their antimatter counterparts, anti-mesons (see “LHC antimatter anomaly hints at new physics”). If this result stands up, it would go a long way towards explaining why we have more matter than antimatter. More importantly, it would prise open the standard model of particle physics – which cannot explain the result – and point the way to yet more new physics.

The widest crack of all concerns a theory once considered outlandish but now reluctantly accepted as the orthodoxy. Almost everything in modern physics, from standard cosmology and quantum mechanics to string theory, points to the existence of multiple universes – maybe 10500 of them, maybe an infinite number (see “The ultimate guide to the multiverse”).

If our universe is just one of many, that solves the “fine-tuning” problem at a stroke: we find ourselves in a universe whose laws are compatible with life because it couldn’t be any other way. And that would just be the start of a multiverse-fuelled knowledge revolution.

Conclusive evidence may be close at hand. Theorists predict that our universe might once have collided with others. These collisions could have left dents in the cosmic microwave background, the universe’s first light, which the European Space Agency’s Planck satellite is mapping with exquisite precision. The results are eagerly awaited, and could trigger a revolution not unlike the ones unleashed by Copernicus’s idea that the Earth is not the centre of the solar system and Edwin Hubble’s discovery that our galaxy is just one among many in an expanding universe.

These are exciting, possibly epoch-making, times. Our understanding of the universe stands on the brink of being remade once again. The universe may indeed be queerer than we can suppose, but that was never going to stop us from trying.

Universo espelho

Seven (and a half) reasons to believe in Mirror Matter: From neutrino puzzles to the inferred Dark matter in the Universe

R. Foot
(Submitted on 16 Feb 2001 (v1), last revised 2 Mar 2001 (this version, v2))

Parity and time reversal are obvious and plausible candidates for fundamental symmetries of nature. Hypothesising that these symmetries exist implies the existence of a new form of matter, called mirror matter. The mirror matter theory (or exact parity model) makes four main predictions: 1) Dark matter in the form of mirror matter should exist in the Universe (i.e. mirror galaxies, stars, planets, meteoroids…), 2) Maximal ordinary neutrino – mirror neutrino oscillations if neutrinos have mass, 3) Orthopositronium should have a shorter effective lifetime than predicted by QED (in “vacuum” experiments) because of the effects of photon-mirror photon mixing and 4) Higgs production and decay rate should be 50% lower than in the standard model due to Higgs mirror – Higgs mixing (assuming that the seperation of the Higgs masses is larger than their decay widths). At the present time there is strong experimental/observational evidence supporting the first three of these predictions, while the fourth one is not tested yet because the Higgs boson, predicted in the standard model of particle physics, is yet to be found. This experimental/observational evidence is rich and varied ranging from the atmospheric and solar neutrino deficits, MACHO gravitational microlensing events, strange properties of extra-solar planets, the existence of “isolated” planets, orthopositronium lifetime anomaly, Tunguska and other strange “meteor” events including perhaps, the origin of the moon. The purpose of this article is to provide a not too technical review of these ideas along with some new results.

Comments: minor changes, latex, about 15p
Subjects: Astrophysics (astro-ph); High Energy Physics – Experiment (hep-ex); High Energy Physics – Phenomenology (hep-ph); High Energy Physics – Theory (hep-th)
Journal reference: ActaPhys.Polon.B32:2253-2270,2001
Cite as: arXiv:astro-ph/0102294v2

O Biocosmo Inteligente de Isaac Asimov

Sim, eu confesso. A minha teoria do Demiurgo e muito provavelmente a teoria do Biocosmo de Gardner foram inspiradas diretamente neste clássico conto do Asimov. É curioso que Asimov, um expoente do movimento cético, tenha dado um contraexemplo que refuta completamente a ideia de que a única posição compatível com a ciência seja a filosofia de baixa serotonina de Monod e Weinberg, de um Universo que emerge do Acaso, sem propósito e hostil a Vida. Asimov iniciou a terceira via entre o Teísmo e o Ateísmo.

Isaac Asimov – A Última Pergunta

Postado às 17:48:00 por Vindemiatrix

Aos leitores e, mais enfaticamente, aos amigos que se dedicam a perder um pouco de tempo por aqui, recomendo com o maior prazer a leitura do conto a seguir de Isaac Asimov, na tradução de Luiz Carlos Damasceno Jr.

As imagens criadas por Asimov são de encher a imaginação, as soluções para cada problema apresentado e o desfecho são esplêndidos. Meu dia vai ser melhor só por causa dele.

Isaac Asimov – A Última Pergunta

A última pergunta foi feita pela primeira vez, meio que de brincadeira, no dia 21 de maio de 2061, quando a humanidade dava seus primeiros passos em direção à luz. A questão nasceu como resultado de uma aposta de cinco dólares movida a álcool, e aconteceu da seguinte forma… Read more [+]

Tempos revolucionários na Física

Nos tempos de estudante sempre reverenciávamos os tempos heróicos da Mecânica Quântica e a coragem de seus fundadores. Mas será que realmente gostariamos de viver naquela época de confusão e queda de paradigmas centrais da física classica? Ou será que seriamos mais conservadores e céticos, esperando ver (confirmações definitivas ou um consenso científico) para crer em vez de acreditar que realmente uma nova física estava surgindo?

Roque propôs que se fizesse um estudo estatistico dos papers do ArXiv sobre os neutrinos superluminais. Pelo que vi até agora, dos 113 artigos sobre o assunto no repositorio, não tem nenhum de algum fisico brasileiro. A equipe de fisicos brasileiros que vai acompanhar o experimento MINOS em 2013 já anunciou que é cetica. 

Será que os brasileiros, por herança cultural lusitana, seriam mais conservadores? Cadê a tão propalada criatividade do brasileiro?  

Essa noticia que saiu agora explicaria o ajuste fino de alpha em nossas redondezas. Se alpha varia continuamente, talvez estivessemos em uma regiao critica de transicao: será que o nosso universo é critico e está na borda de uma transicao de fase entre duas regioes, como no caso de uma rede onde um gradiente de p (num modelo de percolacao)  produz p=p-c na borda entre uma regiao percolante e uma regiao nao percolante?


Laws of physics ‘are different’ depending on where you are in the universe

  • Laws we know may be ‘like local by-laws’ say scientists
  • Hints universe is bigger than we think – possibly infinite
  • Other parts of the universe may be hostile to life


Last updated at 12:36 PM on 1st November 2011

The quasar ULAS J1120+0641: Scientists measured the light from distant quasars for the 'signatures' of metal atoms in between us and the distant galactic nuclei - they found that the measurements were different from similar ones on Earth

The quasar ULAS J1120+0641: Scientists measured the light from distant quasars for the ‘signatures’ of metal atoms in between us and the distant galactic nuclei – they found that the measurements were different from similar ones on Earth

The laws of physics may not be as set in stone as previously imagined.

One of the laws of nature seems to vary depending on where in the universe you are, research suggests.

The new analysis of data from Hawaii’s Keck telescope and Chile’s Extremely Large Telescope, could have profound implications for our understanding of the universe.

The ‘constancy’ of physics is one of the most cherished principles in science – but the scientists say that the ‘laws’ we know may be the galactic equivalent of ‘local by-laws’ and things may work quite differently elsewhere.

The discovery – if true – violates one of the underlying principles of Einstein’s theory of General Relativity, and has profound implications for our understanding of space and time.

The findings could mean that the universe is far bigger than we thought – possibly even infinite.

It also means that in other parts of the universe, the laws of physics might be hostile to life – whereas in our small part of it, they seem fine-tuned to supporting it. 

Research carried out at the University of New South Wales (UNSW), Swinburne University of Technology and the University of Cambridge found that one of the four known fundamental forces, electromagnetism – measured by the so-called fine-structure constant and denoted by the symbol ‘alpha’ – seems to vary across the Universe.

The two telescopes at the W.M. Keck Observatory on Mauna Kea on the Big Island of Hawaii. Scientists used data from these, and from the Extremely Large Telescope in Chile to search 300 distant galaxies

The two telescopes at the W.M. Keck Observatory on Mauna Kea on the Big Island of Hawaii. Scientists used data from these, and from the Extremely Large Telescope in Chile to search 300 distant galaxies

The researchers looked at light from distant quasars – huge, bright objects that outshine their host galaxies – to see how the light was absorbed by metallic atoms such as chromium, iron, nickel and zinc on its billion-year journey to us.

The researchers looked at 300 distant galaxies. The experiment found that the atoms in space behaved differently from ones on earth.

‘The results astonished us,’ said Professor Webb. ‘In one direction – from our location in the Universe – alpha gets gradually weaker, yet in the opposite direction it gets gradually stronger.’

‘The discovery, if confirmed, has profound implications for our understanding of space and time and violates one of the fundamental principles underlying Einstein’s General Relativity theory,’ Dr King added.

The scientists used distant quasars - huge, bright galactic nuclei - to 'illuminate' metal atoms in between them and earth. Analysing the light found that they behaved differently from atoms on Earth

The scientists used distant quasars – huge, bright galactic nuclei – to ‘illuminate’ metal atoms in between them and earth. Analysing the light found that they behaved differently from atoms on Earth

The first hints that alpha might not be constant came a decade ago when Professor John Webb and other colleagues at UNSW and elsewhere, analysed observations from the Keck Observatory, in Hawaii. Those observations were restricted to one broad area in the sky.

However, now Webb and colleagues have doubled the number of observations and measured the value of alpha in about 300 distant galaxies, all at huge distances from Earth, and over a much wider area of the sky.

The new observations were obtained using the European Southern Observatory’s ‘Very Large Telescope’ in Chile.

‘Such violations are actually expected in some more modern ‘Theories of Everything’ that try to unify all the known fundamental forces, said Professor Flambaum.

‘The smooth continuous change in alpha may also imply the Universe is much larger than our observable part of it, possibly infinite.’

‘Another currently popular idea is that many universes exist, each having its own set of physical laws,’ Dr Murphy said. ‘Even a slight change in the laws of Nature means they weren’t ‘set in stone’ when our Universe was born.

‘The laws of Nature you see may depend on your “space-time address” – when and where you happen to live in the Universe.’

Professor Webb said these new findings also offer a very natural explanation for a question that puzzled scientists for decades – why do the laws of physics seem to be so finely-tuned for the existence of life?

‘The answer may be that other regions of the Universe are not quite so favourable for life as we know it, and that the laws of physics we measure in our part of the Universe are merely ‘local by-laws’, in which case it is no particular surprise to find life here,’ he said.

Read more: http://www.dailymail.co.uk/sciencetech/article-2056018/Laws-physics-change-depending-universe.html#ixzz1ecjm6rEb

Nosso Universo é um bode castrado?

The F-Landscape: Dynamically Determining the Multiverse

Tianjun LiJames A. MaxinDimitri V. NanopoulosJoel W. Walker
(Submitted on 1 Nov 2011)

We evolve our Multiverse Blueprints to characterize our local neighborhood of the String Landscape and the Multiverse of plausible string, M- and F-theory vacua. Building upon the tripodal foundations of i) the Flipped SU(5) Grand Unified Theory (GUT), ii) extra TeV-Scale vector-like multiplets derived out of F-theory, and iii) the dynamics of No-Scale Supergravity, together dubbed No-Scale F-SU(5), we demonstrate the existence of a continuous family of solutions which might adeptly describe the dynamics of distinctive universes. This Multiverse landscape of F-SU(5) solutions, which we shall refer to as the F-Landscape, accommodates a subset of universes compatible with the presently known experimental uncertainties of our own universe. We show that by secondarily minimizing the minimum of the scalar Higgs potential of each solution within the F-Landscape, a continuous hypervolume of distinct minimum minimorum can be engineered which comprise a regional dominion of universes, with our own universe cast as the bellwether. We conjecture that an experimental signal at the LHC of the No-Scale F-SU(5) framework’s applicability to our own universe might sensibly be extrapolated as corroborating evidence for the role of string, M- and F-theory as a master theory of the Multiverse, with No-Scale supergravity as a crucial and pervasive reinforcing structure.

Comments: 15 Pages, 7 Figures, 1 Table
Subjects: High Energy Physics – Phenomenology (hep-ph); Cosmology and Extragalactic Astrophysics (astro-ph.CO); High Energy Physics – Theory (hep-th)
Report number: ACT-18-11; MIFPA-11-49
Cite as: arXiv:1111.0236v1 [hep-ph]



Thanks to my last post,  I found a financial word of the day email and subscribed to it. Couldn’t hurt, I thought. “Bellweather” was the very first one, which did not, shall we say, instill confidence. In one of my rare moments of non-ignorance, I actually know that the word is “bellwether”, not “bellweather”. I know this almost exclusively because I read the Connie Willis book of the same name. The book is not her best (I’d say that honor might go to To Say Nothing of the Dog or Doomsday Book, though friends report that her latest ones, Black Out and it’s sequel, the just released All Clear, about WWII England are up to that high bar.) Bellwether, though, is really good in its exploration of its title concept.

The bellwether is, to my understanding, the sheep that leads the drift of the flock. As a metaphor,  it’s maybe something like the trendsetter, or the avant garde. Willis’s novel is partly about trying to figure out about how the bellwether is selected. I think I’ll avoid spoilers around this one, as at the very least, there is a very interesting hypothesis proposed about this. Read more [+]

O Multiverso está na moda

Editorial Reviews

Amazon.com Review

There’s a reason “astronomically large” means “larger than the scale of ordinary life”: normal scales of time and space for astronomers involve millions of years and anywhere from thousands to quadrillions of kilometers. Even for astronomers, University of Michigan professor Fred Adams and his former student Greg Laughlin think big–really, really big–and their planning is really, really long-term.

In The Five Ages of the Universe, Adams and Laughlin present their vision of the history of the universe, from the big bang on. They’ve had to come up with a new unit of measure to make this timescape intellectually tractable: the “cosmological decade.” When the universe is 10 to the n years old, it is in the nth cosmological decade; we are now in the 10th, for instance. Each decade is thus 10 times as long as the one before.

All the stars will have stopped shining in the 14th cosmological decade, about 100 trillion years from now–which is a mind-bendingly long period of time by most standards. But Adams and Laughlin are just getting their speculations warmed up. They go on to fold, spindle, and mutilate your time sense as they discuss the Degenerate Era (out to decade 39), the Black Hole Era (to decade 100), and the possible creation of new universes in the Dark Era (after decade 101 or so). It’s the most fascinating, mind-expanding trip inside eternity you can read. –Mary Ellen Curtin

From Publishers Weekly

Piling one layer of speculation upon another yet retaining a disciplined, scientific approach, astrophysicists Adams (University of Michigan) and Laughlin (UC-Berkeley) take readers on a cosmic adventure to a time in the unimaginably distant future. They view time not in linear years but in logarithmic cosmological decades. We live early in the 10th cosmological decade, approximately 10 billion (10 to the 10th power) years since the Big Bang. For the first six cosmological decades, the Primordial Era, the authors explain, an intensely hot universe expanded and cooled. Elementary particles formed, followed by atoms and molecules. The stage was set for the present Stelliferous Era of galaxies, stars and planets that will continue through the 14th cosmological decade. Our universe will then be 10,000 times its present age, and even its slowest-burning stars will have used up their nuclear fuel. Stellar remnants will dominate the next 25 cosmological decades, the Degenerate Era. Following that will be the Black Hole Era, more than 60 cosmological decades long. The final chapter will be the Dark Era, a steadily diminishing, infinitely long decline toward universal equilibrium. The authors speculate on the survival of intelligent life through the entire history. They also discuss the evolution of universes in Darwinian terms. Many readers will reach their saturation point for conjecture well before those final sections, but others, especially science fiction buffs, will savor every lengthening, darkening, diminishing epoch leading to the authors’ concluding vision: the birth of new universes more than 100 cosmological decades after ours burst into existence. (June)
Copyright 1999 Reed Business Information, Inc.

See all Editorial Reviews

Eu queria ter a coragem do Milan M. Ćirković…

Web Corner


Milan M. Ćirković



Senior Research Associate

Astronomical Observatory of Belgrade

Volgina 7

11160 Belgrade-74



Associate Professor

Department of Physics

University of Novi Sad

Trg Dositeja Obradovića 4

21000 Novi Sad



Phone: +381-11-3089079

E-mail: [email protected]



 Serbian version coming soon!


Having some sort of web page since 1994 (long ago by Internet standards), I’ve recently concluded that all complicated and fancy webpage stuff is truly unnecessary and usually annoying. Therefore, I’ve decided to keep this page as simple as possible. While I haven’t yet reached the laudable simplicity of my colleague, pen-friend, and an outstanding polymath Cosma Shalizi, that certainly remains a goal worth striving for!


Professional interests of mine:


Astrobiology and SETI studies

Evolution of galaxies and baryonic dark matter

Philosophy of science, especially philosophy of cosmology and quantum mechanics

Future studies, in particular related to existential risks and transhumanism

History of physical sciences


Selected recent publications (sometimes only penultimate drafts are linked, the “official” versions could be accessed e.g., via KoBSON, one of the best things which happened in local science in decades!):


NEW! Two books of mine have appeared in recent months, notably  (Oxford UniversityPress) and  (University of Novi Sad). Do contact me for details!

NEW! Against the Empire. An essay considering a possible evolutionary pathways of advances extraterrestrial/future human civilizations.Journal of the British Interplanetary Society, vol. 61, in press (2008).

NEWOn the Timescale Forcing in Astrobiology. Branislav Vukotić and Milan M. Ćirković (2007): Serbian Astronomical Journal, vol. 175, pp. 45-50.

Evolutionary Catastrophes and the Goldilocks Problem. International Journal of Astrobiology, vol. 6, pp. 325-329 (2007).

Too Early? On the Apparent Conflict of Astrobiology and CosmologyBiology and Philosophy, vol. 21, pp. 369-379 (2006).

Physics vs. Semantics: A Puzzling Case of a Missing Quantum Theory. Foundations of Physics, vol. 35, pp. 817-838 (2005).

Adaptationism Fails to Resolve Fermi’s Paradox. Serbian Astronomical Journal (peruse HERE!), vol. 170, pp. 89-100 (2005) – with Ivana Dragićević and Tanja Berić-Bjedov.

 “Permanence” – An Adaptationist Solution to Fermi’s Paradox? Journal of the British Interplanetary Society, vol. 58, pp. 62-70 (2005) – recently featured in New York Review of Science Fiction, vol. 17, issue 202, pp. 1-6!

On the Temporal Aspect of the Drake Equation and SETIAstrobiology, vol. 4, pp. 225-231 (2004).

Agencies, Capacities, and Anthropic Self-Selection. Philosophical Writings, vol. 27 (Autumn 2004), pp. 43-62 (2004).

The Anthropic Principle and the Duration of the Cosmological Past. Astronomical and Astrophysical Transactions, vol. 23, pp. 567-597 (2004).

HIGHLY RECOMMENDED! Resource Letter PEs-1: Physical eschatology. (2003): American Journal of Physics, vol. 71, pp. 122-133 (2003).


Complete (and likely out-of-date!) CV with all publications is available here in .pdf format (345 Kb).


Current activities:


Currently preparing an academic book for Oxford University Press on “Global Catastrophic Risks” with Prof. Nick Bostrom as co-editor. To be published (hopefully!) by June 2008.

With Robert J. Bradbury, I am working on “migration hypothesis” a particular solution to Fermi’s paradox, attempting to join postbiological digital perspective to the current SETI studies. The latest version of the preprint can be read here. All comments are welcome!

In collaboration with Prof. Ivana Dragićević, I’m working on a critical study of the so-called Carter’s anthropic argument in astrobiology.

In collaboration with Ivana Damjanov, a grad student, I’m studying future star formation history of spiral disks, notably the duration of the era of conventional star formation (stelliferous era).

Some educational material related to the mini-course I teach on issues in philosophy of science can be found here (in Serbian).

With Drs. Zorica Cvetković and Zoran Knežević, I am preparing the Proceedings of the XIV National Conference of Astronomers of Serbia and Montenegro.




I am PI of the project #146012 “Gaseous and Stellar Components of Galaxies: Interaction and Evolution” financed by the Ministry of Science of the Republic of Serbia in the 2006-2010 period, with 9 co-investigators… UPDATE: I have happily resigned as PI in favor of my great friend and collaborator, Dr. Srdjan Samurović, which will give me much more time to devote to research and other fun and games!

…and member of more professional organizations and societies than I really wish (or need!), so I won’t list them here.



Most frequently used Web resources:


NASA ADS Query Form

ArXiv preprints

Philosophy of science preprints

KoBSON – Konzorcijum biblioteka Srbije za objedinjenu nabavku (subsuming various individual services, like SCOPUS, JSTOR, etc.)

Astronomy journals

Web of Science

Physics Around the World



Lighter stuff:


B92 – Internet, Radio i TV stanica

Apolyton Civilization Site

The Postmodernism Generator



More links on the dedicated page!



– friends and other interesting people


– useful links and resources






“The supreme accomplishment is to blur the line between work and play.”

                                                                                      Arnold J. Toynbee (1889–1975), British historian and philosopher

Por que juntar as palavras Deus e Física dá dinheiro?

Já que desisti de ganhar o prêmio Nobel, vou ver se pelo menos ganho o Prêmio Templeton (que vale 3/2 do Nobel e é divulgado na mesma semana!). Na verdade, se vocês pensarem bem, acho que de todos os físicos brasileiros, eu sou o que mais entende de Teologia.

PS: Se você é físico brasileiro e entende mais de Teologia do que eu, por favor me escreva aí nos comentários, para escrevermos a quatro mãos aquele livro que vai ganhar o Prêmio Templeton!

29/09/2011 – 11h00

Matemático polemiza em “Por que a Ciência Não Consegue Enterrar Deus”

da Livraria da Folha

O matemático britânico John C. Lennox, da Universidade de Oxford, defende com argumentos sólidos a possibilidade de coexistência entre o conhecimento científico e a religião em “Por que a Ciência Não Consegue Enterrar Deus”. O objetivo do livro é fornecer um amparo fortemente embasado para os cientistas, ou qualquer leitor, que sintam necessidade de debater em favor de sua crença.

Matemático tenta comprovar que ciência e Deus não são excludentes
Matemático tenta comprovar que ciência e Deus não são excludentes

Read more [+]

Extensões do Modelo Padrão com Quebra de simetria de Lorentz e neutrinos superluminais

Standard-Model Extension

From Wikipedia, the free encyclopedia

Standard-Model Extension (SME) is an effective field theory that contains the Standard ModelGeneral Relativity, and all possible operators that break Lorentz symmetry.[1][2][3][4][5][6][7][8] Violations of this fundamental symmetry can be studied within this general framework. CPT violation implies the breaking of Lorentz symmetry,[9] and the SME includes operators that both break and preserve CPT symmetry.[10][11][12]




In 1989, Alan Kostelecký and Stuart Samuel proved that interactions in string theories could lead to the spontaneous breaking of Lorentz symmetry.[13] Later studies have indicated that loop-quantum gravity, non-commutative field theories, brane-world scenarios, and random dynamics models also involve the breakdown of Lorentz invariance.[14] Interest in Lorentz violation has grown rapidly in the last decades because it can arise in these and other candidate theories for quantum gravity. In the early 1990s, it was shown in the context of bosonicsuperstrings that string interactions can also spontaneously break CPT symmetry. This work[15] suggested that experiments with kaon interferometry would be promising for seeking possible signals of CPT violation due to their high sensitivity.

The SME was conceived to facilitate experimental investigations of Lorentz and CPT symmetry, given the theoretical motivation for violation of these symmetries. An initial step, in 1995, was the introduction of effective interactions.[16][17] Although Lorentz-breaking interactions are motivated by constructs such as string theory, the low-energy effective action appearing in the SME is independent of the underlying theory. Each term in the effective theory involves the expectation of a tensor field in the underlying theory. These coefficients are small due to Planck-scale suppression, and in principle are measurable in experiments. The first case considered the mixing of neutral mesons, because their interferometric nature makes them highly sensitive to suppressed effects.

In 1997 and 1998, two papers by Don Colladay and Alan Kostelecký gave birth to the minimal SME in flat spacetime.[1][2] This provided a framework for Lorentz violation across the spectrum of standard-model particles, and provided information about types of signals for potential new experimental searches.[18][19][20][21][22]

In 2004, the leading Lorentz-breaking terms in curved spacetimes were published,[3] thereby completing the picture for the minimal SME. In 1999, Sidney Coleman and Sheldon Glashowpresented a special isotropic limit of the SME.[23] Higher-order Lorentz violating terms have been studied in various contexts, including electrodynamics.[24]

[edit]Lorentz transformations: observer vs. particle

Lorentz violation implies a measurable difference between two systems differing only by a particle Lorentz transformation. The distinction between particle and observer transformations is essential to understanding Lorentz violation in physics.

In special relativity, observer Lorentz transformations relate measurements made in reference frames with differing velocities and orientations. The coordinates in the one system are related to those in the other by an observer Lorentz transformation — a rotation, a boost, or a combination of both. Both observers will agree on the laws of physics, since this transformation is simply a change of coordinates. On the other hand, identical experiments can be rotated or boosted relative to each other, while being studied by the same inertial observer. These transformations are called particle transformations, because the matter and fields of the experiment are physically transformed into the new configuration.

In a conventional vacuum, observer and particle transformations can be related to each other in a simple way—basically one is the inverse of the other. This apparent equivalence is often expressed using the terminology of active and passive transformations. The equivalence fails in Lorentz-violating theories, however, because fixed background fields are the source of the symmetry breaking. These background fields are tensor-like quantities, creating preferred directions and boost-dependent effects. The fields extend over all space and time, and are essentially frozen. When an experiment sensitive to one of the background fields is rotated or boosted, i.e. particle transformed, the background fields remain unchanged, and measurable effects are possible. Observer Lorentz symmetry is expected for all theories, including Lorentz violating ones, since a change in the coordinates cannot affect the physics. This invariance is implemented in field theories by writing a scalar lagrangian, with properly contracted spacetime indices. Particle Lorentz breaking enters if the theory includes fixed SME background fields filling the universe.

[edit]Building the SME

The SME can be expressed as a lagrangian with various terms. Each Lorentz-violating term is an observer scalar constructed by contracting standard field operators with controlling coefficients called coefficients for Lorentz violation. Notice that these are not parameters of the theory, since they can in principle be measured by appropriate experiments. The coefficients are expected to be small because of the Planck-scale suppression, so perturbative methods are appropriate. In some cases, other suppression mechanisms could mask large Lorentz violations. For instance, large violations that may exist in gravity could have gone undetected so far because of couplings with weak gravitational fields.[25] Stability and causality of the theory have been studied in detail.[26]

[edit]Spontaneous Lorentz symmetry breaking

In field theory, there are two possible ways to implement the breaking of a symmetry: explicit and spontaneous. A key result in the formal theory of Lorentz violation, published byKostelecký in 2004, is that explicit Lorentz violation leads to incompatibility of the Bianchi identities with the covariant conservation laws for the energy-momentum and spin-density tensors, whereas spontaneous Lorentz breaking evades this difficulty.[3] This theorem requires that any breaking of Lorentz symmetry must be dynamical. Formal studies of the possible causes of the breakdown of Lorentz symmetry include investigations of the fate of the expected Nambu-Goldstone modes. Goldstone’s theorem implies that the spontaneous breaking must be accompanied by massless bosons. These modes might be identified with the photon,[27] the graviton,[28][29] spin-dependent interactions,[30] and spin-independent interactions.[25]

[edit]Experimental searches

The possible signals of Lorentz violation in any experiment can be calculated from the SME.[31][32][33][34][35][36] It has therefore proven to be a remarkable tool in the search for Lorentz violation across the landscape of experimental physics. Up until the present, experimental results have taken the form of upper bounds on the SME coefficients. Since the results will be numerically different for different inertial reference frames, the standard frame adopted for reporting results is the Sun-centered frame. This frame is a practical and appropriate choice, since it is accessible and inertial on the time scale of hundreds of years.

Typical experiments seek couplings between the background fields and various particle properties such as spin, or propagation direction. One of the key signals of Lorentz violation arises because experiments on Earth are unavoidably rotating and revolving relative to the Sun-centered frame. These motions lead to both annual and sidereal variations of the measured coefficients for Lorentz violation. Since the translational motion of the Earth around the Sun is nonrelativistic, annual variations are typically suppressed by a factor 10−4. This makes sidereal variations the leading time-dependent effect to look for in experimental data.[37]
Measurements of SME coefficients have been done with experiments involving:

All experimental results for SME coefficients are tabulated in the Data Tables for Lorentz and CPT Violation.[38]

[edit]External links

[edit]See also

Neutrinos superluminais: Aposta fechada com Jorge Stolfi da UNICAMP!

JorgeStolfi Jorge Stolfi

@osamekinouchi O que eu quero dizer é que é muito difícil enxergar os erros em seu próprio trabalho.
Jorge Stolfi

JorgeStolfi Jorge Stolfi

@osamekinouchi Cena que já vi muitas vezes: “Prof, faz dois dias que procuro o bug neste programa! Começo fazendo… ah! Achei!”
Jorge Stolfi

JorgeStolfi Jorge Stolfi

@osamekinouchi Topo. Até a vista…
Jorge Stolfi

JorgeStolfi Jorge Stolfi

@osamekinouchi Não, eu sou computeiro.
Jorge Stolfi

JorgeStolfi Jorge Stolfi

@osamekinouchi Eu aposto uma pizza que a distância (provavelmente) ou tempo estão errados. Em que cidade vocẽ mora?
Jorge Stolfi

JorgeStolfi Jorge Stolfi

@osamekinouchi De fato. 😎 Mas a profissão de cientista obriga a procurar cuidadosamente erros experimentais, nossos ou dos outros.
Jorge Stolfi

JorgeStolfi Jorge Stolfi

@osamekinouchi Gozado como físicos só discutem como corrigir Einstein, em vez de analisar se a medida da distância está correta.
Bê Neviani

Be_neviani Bê Neviani

Ainda sobre o bolão dos neutrinos t.co/6JDL6e3C rt@osamekinouchi //#ueba e c/participação especial do@universofisico #twitciencia
osamekinouchi osamekinouchi
A verdade está na fora: ArXiv.orgsemciencia.haaan.com/?p=1135
osamekinouchi osamekinouchi

@JorgeStolfi Ou seja, a explicacao tipo Navalha de Occam nao será trivial. E a teoria de inferencia estatistica diz que a Navalha falha…
osamekinouchi osamekinouchi

@JorgeStolfi Jorge, eu acho que qualquer explicacao nao será facil pois os caras sao bons e procuraram por 6 meses por erros sistematicos
osamekinouchi osamekinouchi

@JorgeStolfi Ou seja, a explicacao tipo Navalha de Occam nao será trivial. E a teoria de inferencia estatistica diz que a Navalha falha…
osamekinouchi osamekinouchi

@JorgeStolfi Jorge, eu acho que qualquer explicacao nao será facil pois os caras sao bons e procuraram por 6 meses por erros sistematicos
osamekinouchi osamekinouchi
@JorgeStolfi O comentarista supos que neutrinos interagiriam fracamente pares virtuais, de modo que c<c´<C onde c´=velocidade dos neutrinos
osamekinouchi osamekinouchi

@JorgeStolfi Eu gostei da ideia de que a luz interage com os pares eletron-positron virtuais de modo que c < C, onde C é a velocidade limite
osamekinouchi osamekinouchi
@JorgeStolfi Já sei! Me convide para dar um talk sobre o indice de Garfield-Hirsch, que é bem melhor que o indice de Hirsch!
osamekinouchi osamekinouchi
@JorgeStolfi Vc é quimico, nao? Eu sou amigo do Sergio Galembeck. Devo ir para campinas até o final do ano…
osamekinouchi osamekinouchi

@JorgeStolfi Ribeirao Preto: Eu aceito, mas tem que ser uma pizza + um kit de cervejas Colorado (R$ 40,00)
osamekinouchi osamekinouchi

@JorgeStolfi Jorge, acho que agora a questao é se o efeito é real, uma verdadeira anomalia ou apenas um erro sistematico.
osamekinouchi osamekinouchi

@JorgeStolfi As for me, I have just enough confidence about the multiverse to bet the lives of both Andrei Linde and Martin Rees’s dog.“
osamekinouchi osamekinouchi
Martin Rees said that he was sufficiently confident about the multiverse to bet his dog’s life while Linde said he would bet his own life
osamekinouchi osamekinouchi
@JorgeStolfi Weinberg em Living in the Multiverse: “He said it: A truly committed scientist will bet just about anything …”
osamekinouchi osamekinouchi
@JorgeStolfi A medida da sua crença ou ceticismo é dada por quanto você está disposto a apostar… rs R$ 100 nao é muito!

Ainda sobre o bolão dos neutrinos

Olá Osame,
Sou avesso a apostas e bolões : – ) Não participo nem em Copa do Mundo. Mas vou confessar que torço para que o sinal do OPERA revele-se um erro sistemático ou, se for mesmo confirmado, alguém apareça com uma explicação MUITO boa que acabe salvando o princípio da causalidade.

  • okinouchi disse:


    Não sei por que mas acho que a comunidade anda muito conservadora. Por anos ficamos reclamando que a física anda muito parada, que não há nada de novo, que seria legal o LHC começar logo a revelar “física nova”. Mas física nova, por definição, é a física que abala e mesmo muda o paradigma anterior.

    Eu vejo as pessoas se comportarem como Lorentz que, mesmo a trasnformação tendo o seu nome, nao aceitou a relatividade e acreditou no eter até o final da vida.

    Eu gostei do comentario de um dos caras acima, em que ele propoe que, dado que fótons interagem com os pares eletron-positrons virtuais, ou seja, dado que o vácuo quantico (nao previsto pela Relatividade) se comporta como um dielétrico, a luz teria uma velocidade na verdade um pouco menor de a velocidade limite C (vamos usar C maiusculo e reservar c minusculo para a medida da velocidade da luz em laboratorio, OK?).

    Já no caso dos neutrinos, eles nao interagiriam com os pares eletron-pósitrons, de forma que sua velocidade estaria proxima de C (mesmo levando em conta que eles possuem massa nao nula).

    Me explica uma coisa: em teoria de campo, os neutrinos sao descritos por um campo spinorial? Eles seguem a equação de Dirac? Ou é melhor descrever em termos de segunda quantização? Mas de que tipo de campo? Ainda um campo spinorial de spin 1/2 ?

    Outra duvida: Com quantas casas decimais se pode medir a velocidade da luz c antes que as correcoes quanticas via interacao com os pares virtuais se façam sentir? Se a constante c for universal, isso significa que eu posso medir infinitas casas decimais (ou seja, é um problema apenas de tecnologia de medição?). Ou existe um limite fundamental para o numero de casas decimais que se pode medir nas constantes fisicas (ao contrario das constantes matematicas tipo /pi)?

    Eu ouvi falar que a convenção de tomar c = 1 pode ser conveniente mas está, em termos fisicos, errada, pois supoe, por exemplo, que c(t) = c = cte a priori, e teoricamente isto nao é justificavel (por exemplo, a teoria VLS (variable light speed) de João Magueijo, que é a concorrente da teoria da Inflação, postula que não houve inflação no inicio do Big Bang mas apenas que c era muito maior no inicio do Universo… Ver o video sensacional: http://www.youtube.com/watch?v=ig-50Rz_Q1Q


    Por outro lado, se Einstein estivesse vivo hoje, acho que ele estaria super excitado, afinal ele reclamava que “Sempre gostei de contestar autoridades, e a vida, para me punir, me tornou uma”… ou algo assim, estou lembrando a citação de cabeça…

    Dado que voce comentou, eu imagino que você optou pelo item B. Neste caso, veremos o resultado no dia 21 de dezembro deste ano, OK?

    Usarei os R$ 100 seus para me ajudar a comprar o telescópio que meus filhos me pediram…

Standard-Model Extension

From Wikipedia, the free encyclopedia

Standard-Model Extension (SME) is an effective field theory that contains the Standard ModelGeneral Relativity, and all possible operators that break Lorentz symmetry.[1][2][3][4][5][6][7][8] Violations of this fundamental symmetry can be studied within this general framework. CPT violation implies the breaking of Lorentz symmetry,[9] and the SME includes operators that both break and preserve CPT symmetry.[10][11][12]



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