The science magazine Seed is being relaunched, and the first issue of its new incarnation is now on the newsstands. Their motto is “Science is Culture”, and Clifford Johnson over at Cosmic Variance has an enthusiastic appreciation of what they are doing. The magazine is strikingly attractive, with impressive photography and graphics. One photo essay pairs photos with important equations.

There’s a piece by Lisa Randall promoting her recent work with Andreas Karch on what she calls the “relaxation principle”. I guess this is meant to be a sort of vacuum selection principle, contrasted to the “anthropic principle”. In her Seed article she describes what she is doing as follows :

* The challenge for physicists, and the problem I tackle in my own work, is find all possible qualitatively different universes — and to search for principles that determine which of these universes is most likely to exist.*

Unfortunately there seem to be an infinite variety of possible such universes, and examining them all could easily take up the efforts of all particle theorists for the next few centuries. There’s zero evidence for any sort of vacuum selection principle that will pick out the standard model from this infinite array of possibilities, so setting out on this path means probably abandoning any hope for ever explaining much of anything about particle physics. Karch and Randall try to give an argument for why there are 3 space dimensions, ending up with an argument for the survival of both 3 and 7 dimensional branes if one starts out with branes of all dimensions. This is a very, very long way from getting any non-trivial information about particle physics.

This issue of the magazine also has a short piece entitled “A New Force? How blogs are revolutionizing physics” by Joshua Roebke, an ex-string cosmology graduate student who now works at Seed. Joshua devotes a sizable part of his piece to telling about “Not Even Wrong” and some of the effects it has been having. Earlier this summer I had lunch with him here in New York and was encouraged to see that Seed has someone on staff with a good theoretical physics background.

**Update:** Lubos Motl also has a posting about the new Seed magazine. He comments on the Karch-Randall “relaxation principle”, saying that he “kind of worked on it”, but

* frankly, I don’t really believe it – because of the devil hiding in the details that just don’t seem to work – much like many other proposals that have appeared in recent years.*

What utter nonsense! As if Newton or Kepler or even Aristotle or Belushi had the complete hubris to enumerate all possible uni…

Wait! I am suddenly filled with the Randallian spirit! I too can enumerate the possible universes!

ONE.I tire of these loathsome exercises in narcissism.

-drl

Hello Peter,

I forget if i’ve asked this before, but apart from SUSY, higher-dimensional geometries, and string theory, what are plausible ideas for going beyond the standard model (or explaining the SM) that do not involve string theory, SUSY, and higher-dimensions? Why is it we never hear about them?

I know I did ask about other QG’s such as LQG and CDT, but are there other ideas in particle physics that do not involve string theory?

I forget if i’ve asked this before, but apart from SUSY, higher-dimensional geometries, and string theory, what are plausible ideas for going beyond the standard model (or explaining the SM) that do not involve string theory, SUSY, and higher-dimensions? Why is it we never hear about them?One reason why you have never heard about them is that they have been starved out. When I was applying for post-docs around 84-85 just about everyone seemed to be switching to Superstring theory, and if you did not want to join the 10/26-dimensional circus yourself, you were unlikely to be shortlisted for a job.

I forget if i’ve asked this before, but apart from SUSY, higher-dimensional geometries, and string theory, what are plausible ideas for going beyond the standard model (or explaining the SM) that do not involve string theory, SUSY, and higher-dimensions? Why is it we never hear about them?For plausible ideas for goung beyond the standard model and explaining it see my homepage at

http://www.physics.helsinki.fi/~matpitka/

and my blog site TGD diary at http://matpitka.blogspot.com/.

Matti Pitkanen

Dan, given that essentially all experiments are well described by the standard model coupled to gravity, perhaps the ultimate ToE will turn out to be SM coupled to GR. If so, the quest for something beyond the SM (except for gravity) would turn out to be fundamentally misguided.

Sure, this theory has some well-known mathematical problems – QM and GR are incompatible, the SM is somewhat ugly in the Higgs sector, QED breaks down at the Landau pole, etc. But these problems are mathematical rather than physical in nature, and may very well be resolved with a better mathematical understanding of field theory. At least we know that the mathematics underlying field theory is related to real physics.

How about the most conservative approach of all, yet another parton layer, i.e. quark and lepton substructure?

http://cosmicvariance.com/2005/09/05/dark-matter-and-extra-dimensional-modifications-of-gravity/#comment-4091

Adding another parton layer is hardly conservative. As in string theory and supersymmetry, you have to posit the existence of an invisible world for which there is zero experimental evidence. But unlike string theory, you cannot argue that field theory infinities are absent, so GR will still be unrenormalizable. So you sacrifice the connection to reality without gaining anything mathematically.

Technicolor is a variant of this idea. Here it is the Higgs boson which is a bound state of fermions (unless my memory fails me here), much like Cooper pairs in superconductivity. The experimental status is similar to that of SUSY and strings: the simplest and natural models are ruled out by experiment, but by adding new parameters you can avoid confrontation with experiment forever.

TL, that’s more or less the end of that idea 🙂

I wonder why such simple reasoning is in such short supply? …

-drl

re Thomas Larsson Says:

one of the motivations for going beyond SM+GR is that certain astronomical phenomena appear to be unexplained, and i am referring specifically to dark matter, dark energy, cosmological constant, hierarchy problem, matter/antimatter asymmetry, BH information paradox, etc., that string theory and LQG are attempting to address.

is your position that SM+GR can eventually explain the above phenomena and will not require new physics? if so why all the effort being poured into string theory?

One of the things – no,

thething I enjoyed most about Peter’s forthcoming book (he kindly gave me a copy of the manuscript in January) was an honest survey of the various schemes, stringy and non-stringy, for going beyond or fixing the problems in the standard model. All too often the state of each particular art is explained by one of its enthusiastic exponents, and one gets somewhat of the Monty Python Pet Shop Owner effect (“No, this parrot’s not dead, he’s resting … pining for the fjords, etc.”)WoW! Off topic but eye popping:

a post by Martin Rocek at Lubos’ website.

> Adding another parton layer is hardly conservative.

Yes it is.

> As in string theory and supersymmetry, you have to posit the

> existence of an invisible world for which there is zero

> experimental evidence.

You miss the little detail that unlike strings, an underlying parton structure would not need to wait until the Planck scale in order to reveal itself. As for zero experimental evidence, what do you make of the anomalous magnetic moment of the muon? It’s already been pointed out that it can easily be accomodated by a composite muon.

> But unlike string theory, you cannot argue that field theory

> infinities are absent, so GR will still be unrenormalizable.

Who said partons are supposed to fix GR? By the same logic, quarks are no good since they don’t fix GR either.

> So you sacrifice the connection to reality without gaining

> anything mathematically.

Seems to me somebody is confusing mathematics with reality here…

GR+SM as formulated today is certainly not the end of the story. Astronomical observations are a minor problem here, compared to the fact that the two theories are mutually incompatible. However, there are good reasons to expect that a deeper understanding of the mathematics underlying QFT can lead to a unification of QM and GR, without adding much on the physics side.

More specifically, I am thinking about gauge symmetries. Recently I had a look at Rudolf Haag’s book on Local Quantum Physics. A striking claim there is that no intrinsic quantum formulation of the gauge principle is known, despite its central importance in the SM. The gauge principle is of course well understood on the classical level, and that’s what matters in the path-integral formalism. An exception, where a gauge symmetry is understood on the quantum level, is conformal symmetry in string theory.

The lack of such a quantum gauge principle is quite obvious from my point of view. In order to understand how a gauge symmetry acts on the (kinematical) Hilbert space, we must first understand how it can act at all, and this is precisely the subject of the representation theory of gauge algebras. The most striking observation is that all interesting quantum representations have anomalies, and that one must explictly introduce and quantize a clock’s worldline in order to formulate these representations. This appears to me as the key missing idea.

I have of course no real idea how the astronomical observations should be understood, and I think that it may be premature to address that problem without a theory of quantum gravity. However, i would guess that the CC is somehow related to anomalies – this is at least the case in 2D and 3D gravity.

Dissident, quarks are good because they explain many experiments. An extra layer of partons would be equally good if they fixed some glaring cracks in the SM. Last time I checked, there were no such cracks.

Besides, I thought muon g-2 was explained by a sign bug in the Schoonship program.

Really. I guess you should tell these guys then:

http://www.g-2.bnl.gov/

Thomas is right that there was an error in the muon g-2 calculation (I don’t know if Schoonschip was to blame). Fixing the error reduced the difference between the theoretical and experimental values. At this point as far as I can tell, given the uncertainties in the theoretical calculations and in the experimental results, there is no convincing conflict between theory and experiment.

Just for the record, the g-2 for the muon is indeed out by over a sigma from the standard model prediction. However, the errors and stability of the hadronic part of the theory are “questionable”. There’s no reason to expect the hadronic number to stay where it is. In fact, there’s two different hadronic numbers, and they disagree with each other. hep-ph/0402206 is a good place to start.

In short, the hadronic part of the muon mm is way too uncertain to go about claiming a 2 sigma difference is “evidence” of anything.

Thomas Larsson writes:

This ignores the 800-pound gorilla: dark matter! Barring drastic revisions of our theory of gravity, about 23% of the energy density in the universe is dark matter, while only 4% is ordinary matter. (The rest is dark energy – these are the WMAP findings.)

So, while I think it’s

crucialto pay close attention to the details of the Standard Model, I think that someday we’ll find a beautiful theory that includes the Standard Model particlesand a bit more.Looking for this theory is one of my hobbies….

Dark matter? Nah! 🙂

As I have pointed out elsewhere

http://cosmicvariance.com/2005/09/05/dark-matter-and-extra-dimensional-modifications-of-gravity/

there are now several interesting alternatives:

http://arxiv.org/abs/hep-th/0410119

http://arxiv.org/abs/astro-ph/0506370

Almost forgot: the current g-2 deviation from the standard model prediction is 1.6 sigma.

http://www.npl.uiuc.edu/exp/g-2/g-2Main.html

By all means, pooh pooh it all you want. 😉

No matter what I write about, sooner or later people want to start discussing their favorite alternatives to GR. Please don’t do this here, it’s off-topic, and the last thing in the world I want to do is to try and moderate a discussion of this subject.

I’ve had to delete a bunch of such comments, then deal with people complaining about this and accusing me of censorship. This is not sci.physics and I’m not going to let it turn into that.

John Baez wrote:

‘This ignores the 800-pound gorilla: dark matter! Barring drastic revisions of our theory of gravity, about 23% of the energy density in the universe is dark matter, while only 4% is ordinary matter. (The rest is dark energy – these are the WMAP findings.)’

All the evidence for dark matter and dark energy is from cosmology models, so why can’t the basis of cosmology be re-examined? It is entirely possible to incorporate into general relativity a model for gravity which eliminates the dark matter problem (which is due to the false assumption that gravity has no cause within the universe, correcting that just leaves invisible dust contributions), and the dark energy problem results again from ad hoc force-fitting the theory to the observations. This is not the way to do physics. The theory should not keep getting fiddles to make it fit the facts, that is what went wrong with epicycles in ancient cosmology.

Vafa article posted today—-relates to earlier post by Peter on this blog.

Here is the article:

http://www.arxiv.org/abs/hep-th/0509212

The String Landscape and the Swampland

Cumrun Vafa

9 pages

since this post is not on topic, I’d hardly object were it deleted. Just wanted to let folks know in case of interest.