For the latest on the status of the LHC, see the July 2 talk of Steve Myers mentioned here earlier, and a July 8 talk (slides, video) that has some more recent news. The question of what to do about bad splices is still up in the air. The current plan is to make measurements at 80K during the next few weeks on the three sectors that have not been warmed up, then present options during the second week of August to the DG and the experiments. The decision to be made will be about how long to delay the start-up to fix more splices. If more splices get fixed, the machine can safely be run at higher energy. The optimistic scenario now seems to be that it will be possible to run at some energy in the range of 4-5 TeV/beam, without introducing further delays in the current draft schedule (the latest schedule has the machine ready to start circulating beams around the end of October). Gordon Watts has more detail in a recent post, including one of the relevant plots showing the energy vs splice resistance trade-off.
Two items on the multiverse front:
You can turn an egg into an omelet, but not an omelet into an egg. This is good evidence that we live in a multiverse. Any questions?
String theorist Oswaldo Zapata has posted the third part of his essay on the history of superstring theory, dealing with the question of the “beauty” of string theory. Basically he argues that it was only in 1999, after it started to become clear that string theory unification wasn’t working out, that a publicity campaign about the “beauty of string theory” got started:
During the late eighties and early nineties, and motivated by the relative success of the heterotic superstrings, string theorists were submerged in intricate and endless computations trying to recover the standard model using a ‘‘top-bottom’’ approach. At that time no one was talking publicly about a beautiful construct. In fact, the theory was in an ugly impasse and mathematical consistency was the only remote trace of beauty…
In this section we have seen that, in contrast to what is currently claimed, string theory was not always considered to be a beautiful theory. The public recognition of the beauty of the theory is recent, dating from around 1999, and it was due mainly to the convergence of two factors: a favourable context, “internal” and “external,” and an acute sense of opportunism.
From the Publisher’s Weekly review of Graham Farmelo’s life of Dirac:
In 1955, Dirac came up with a primitive version of string theory, which today is the rock star branch of physics.
The opera Hypermusic Prologue: A Projective Opera in seven Planes, libretto by Lisa Randall, had its first performance last month in Paris. It will be presented again in Barcelona in November.
FQXI seems to like to have conferences for their members at scenic volcanic locations in the mid-Atlantic. This year it’s the Azores, here’s their schedule, talks to appear here, blogging here (Sabine Hossenfelder) and here.
Strings 2009 finally got around to putting slides from most of the talks online here. The one talk that seemed to have something new wasn’t about strings, it was Arkani-Hamed’s talk on Holography in Flat Space: Algebraic Geometry and the S-matrix, based on work to appear with Cachazo, Cheung and Kaplan. It’s based on studying the structure of amplitudes in twistor space, and the talk includes many exclamation points, and the claim that “SOME POWERFUL MATHEMATICAL STRUCTURE IS AT WORK!”. More specifically:
Very natural and beautiful mathematical structure – intersection theory and Schubert Calculus – seems to lie at the heart of tree and loop gluon scattering amps!
From the slides it does appear that there’s some nice mathematics at work here, I look forward to seeing the paper.
Citing the last paragraph of the article by Lenonard Susskind:
“Whether string theory with its huge landscape, and eternal inflation with its reproducing pockets of space, will prove to be correct is for the future to decide. What is true is that as of the present time, they provide the only natural explanation of the universe that lives up to the standard set by Darwin.”
Currently I am greatly enyoing his book “An Introduction to Black Holes, Information And The String Theory Revolution”.
How can a capable physicist and author like him write an article like that? This is completly beyond me.
A key of evolution is the survival of the fittest, with the definition of “the fittest” being constantly in danger to become a tautology (“Well, the fittest were the ones that survived, what else?”).
Did Leonard Susskind give somewhere a definition of what being the fittest universe of the multiverse means (boy, I hope it is the one we live in!) and how a process of selection would work?
At least he admits that string theory has still to prove itself.
Peter,
In your opinion, do you think Nima, Cachazo and others are trying to find a non-string quantum gravity, but that uses susy just as a scattering symmetry rule?
you cannot turn an omelet into an egg, but you can turn stupidity into a book.
This is good evidence that we live in a multiverse, because stupidity is infinite and a single universe could not contain all of it.
Daniel,
My understanding is that one motivation is to get some sort of analog of AdS/CFT for flat space (rather than anti-deSitter), but, unlike AdS/CFT, this is supposed to a weak-weak duality, so it’s something very different. The CFT side I guess is N=4 SYM, or maybe N=8 supergravity, but I have no idea what they are expecting on the “AdS” side, other than that it would involve twistor space.
If all the technical problems with the LHC are fixed in time, Murphy’s law suggests that a swine flu outbreak may cause further delays.
“You can turn an egg into an omelet, but not an omelet into an egg…” ergo proof of multiverse.
Bah.
Maybe you or I can’t turn an egg into an omelet, but the universe does this all the time. Or are we to presume eggs came preformed as initial conditions of the big bang? Farmers and chicken coops do this reaction millions of times each day. I’m not being flippant, but pointing out the obvious observation which wrinkles this entire argument. Higher order biological laws create low entropy eggs from initial states with much higher entropy than the proverbial omelet, viz., disordered solutions of amino acids and H2O.
Time’s arrow edit. I meant:
Maybe you or I can’t turn omelets into eggs, but the universe does this all the time…
Jim,
I’m not endorsing the multiverse, but the argument about the second law depending on low entropy in the early Universe is a good one and almost by definition as valid as the second law is.
Chickens do produce eggs daily, but with a significant expenditure of energy. Where does the energy come from? Plants, which derive their energy from the Sun, a star. That the Universe is populated with stars (and is not a much more random structure) is a result of the near-uniformity of matter in the early Universe together with the fact that the gravitational field was of such a special type as to allow that near-uniformity. If a more “random” gravitational field had been there, the form of the Universe would be entirely different (no stars and no chickens, probably).
The near-uniformity of the matter does contribute some entropy, but it is the extreme specialty of the gravitational field which makes the early Universe a low-entropy state (compared to a “random” Universe).
Even Lubos Motl disagrees with Susskind re Anthropic/Darwinism if you check out his website.
Is the situation still as Peter wrote in his book re String Theorists that there are 2 camps: Anthropic (Susskind, Polchinski) and Not-Anthropic (Gross, Witten)?
“How can a capable physicist and author like him write an article like that? This is completely beyond me.” … Tim vB
Might I suggest==> “Cognitive Dissonance?” That’s a psychology term about why the human brain finds it difficult to accept things when evidence is shown that a fast-held belief is wrong. Happens all the time and has no correlation to IQ. Synonyms include “lying to oneself” or “Rationalization.”
Peter’s book explains the Anthropic in String Theory beautifully: in a nutshell, it’s a desperate measure to explain the non-predictive and unfalsifiable String Theory. Essentially, it’s desperation.
Hello Greg,
I know about cognitive dissonance: In the EU every package that contains cigarettes or cigars must by law have a big label saying something like “smoking can kill you” or “smoking can cause cancer” etc.
I once asked a heavy smoker what his opinion of this was, he answered “of what?”.
He had not noticed…(the labels are big, you cannot miss that by chance).
Tim, that’s a nice analogy but I was thinking of Leonard Susskind and String Theory, because as far as I can tell the “String Theory War” is either over or coming to a close, and ST isn’t the winner. Motl, Susskind et. al. will obviously disagree. If the Anthropic Landscape doesn’t spell D-E-S-P-A-R-A-T-I-O-N, what does?
There’s an outside chance (think: Quantum Tunneling) that Witten will bring his incredible intellect back to falsifiable and predictive Physics, indeed I think I see signs (but do not know …. I’m speculating), but I don’t think Susskind ever will. He was there at the beginning, and he strikes me as a very stubborn man. Which isn’t a bad thing all the time, actually. His is also an incredible intellect.
Nor do I think String Theory should completely go away. I just don’t think it will be falsifiable or predictive until 2200, 2300, or even 2400. Can I hear a 2500? Shrug, who knows?
Leonard Susskind will speak at the Holographic Cosmology Conference that will run from tomorrow through the 18th at The Perimeter Institute. I hope Peter or someone links to his talk.
Peter, have you seen this
paper ?
It is an example of a string theorist venturing into LQG.
Thank you for that link, Shantanu, good stuff. I especially liked this line in the abstract:
“This suggest [sic] the possibility of a relation between Loop Quantum Gravity and supersymmetric string theory, where the Barbero-Immirzi parameter and field of the former play the role of the supersymmetric axion in the latter.”
Well, what can we say? Lee Smolin, former author of string theory papers and ever the diplomat, mentions in TTWP that LQG and St need not be combative, but co-operative i.e. complementary, the point being (if I read Lee correctly) that the difference between (some but not all) Strings and LQG is one of scale, with LQG (and Quantum Graphity and CDT especially) operating at the smaller scale.
But good luck trying to get String Theorists (the hardcore ones) to agree with that! Their field has gone from something very specific, namely: trying to explain quarks and the Strong force until Quantum Chromodynamics kicked them to the curb, to getting more and more general until we arrive at the present with Anthropic Landscape, in which case everything is possible and we may as well embrace Many Worlds. Which I will not, nor do I think most reasonable people will.
Please, remember this is not a general physics discussion board, and the owner has a rather limited degree of interest in quantum gravity.
Thank you, Peter, my interest in QG is primarily as a hobby. It’s fascinating, yet not as important as those branches of Mathematics and Physics that push knowledge a bit farther than where we are. It would be nice if we have a 1925-1929 situation where the curtains of ignorance are vastly pushed back, and years such as those may well be in hand, but who knows?
I love your weblog, so much so I couldn’t find time to read your book until a month ago, and of course I am juiced as a rookie reader.
And what can I say about your book; it’s awesome, and pleasantly surprising, as your road to this stuff we’re talking about is the same as mine, from Astronomy to Physics to Mathematics.
Best of luck to you by the way on your exploration of BRST Dirac Cohomology. Sounds enticing.
Specifically, I have completed a 10-month general overview of current Physics/Mathematical physics, and find it is now the time to choose a specialty, with QG forever a hobby that I will spend time on, time willing. I have narrowed it down to the following fields. your opinion, please:
– Math: Representation theory of 4D space-time gauge symmetries and diffeomorphism group representation theory as related in the last two paragraphs of your book. How has that developed since publication. Where is the most current work needed?
– Physics: The Quantum Hall Effect. Low temperature sure, but incredible how the quantum world can be made manifest in the macroscopic. I’ll work on this one by myself, what a puzzle.
Greg,
The paper on Dirac cohomology is intended to be a toy model for the interesting case of 4d. You study representations by studying an invariant, their Dirac cohomology. To do this in 4d requires new ideas: everything is parametrized there by the space of background connections and metrics and you need to figure out what to do about that. Right now I’m thinking about the easier case of 2d…
I think we’re still quite a ways away from even knowing what the right way to think about such representations is, so this is a difficult subject for someone to study. It’s too wide open right now, and the relevant mathematics is not even clear. That quantum Hall effect looks like a much more straightforward problem…
The most relevant application of Darwin’s theory on high-energy physics is the evolution of the physicists landscape. Here, natural selection works through paper publications, and the fittest are those who can keep publishing the most, however meaningless these papers may be. Susskind and his cohorts are successful survivors of this process. Although I admit this result is not pretty, but hey, that’s part of Darwinism.
…..Wait a minute; with the DNA you can identify a person from a million, with ST (and branes), still you cannot do anything concrete just hope for some right arrangement to be correct. Sorry but lame analogy.