# The Landscape at Davis

I’m in Nothern California this week, and have been attending some of the talks at the conference at UC Davis celebrating Albert Schwarz’s 70th birthday. The landscape at Davis is exceedingly flat, but this morning Lenny Susskind gave a remarkable talk with the title “Exploring the Landscape”.

It was a pretty strange talk for a mathematical physics conference since it contained zero mathematics (and it’s arguable whether there was any physics…). Susskind blamed Iz Singer for this, claiming that Singer told him he should talk about the landscape stuff since it was leading to a new mathematical field of “statistical topology”. He began by holding up a copy of Steven Weinberg’s “Dreams of a Final Theory” and reading a quote from it about the cosmological constant. He liked this so much he read the same quote a second time a little while later.

He then discussed some of the recent history of string theory, noting that for a long time string theorists were hoping for a mathematical silver bullet that would provide a more or less unique solution to the theory that looked like the real world. He announced that now the probability of this is less than 1 in 10^500.

Susskind then explained a bit about KKLT vacua, saying that his main reason for discussing them was to show how silly and inelegant they are. He compared them to a Rube Goldberg machine and called Shamit Kachru the “master Rube Goldberg architect”.

The most dramatic part of Susskind’s talk was something new: an attack on the idea of low-energy supersymmetry. He explained the standard fine-tuning argument for supersymmetry, but then indicated that he thought an anthropic argument made more sense. The reason the Higgs mass is so much smaller than the Planck mass is not supersymmetry, but instead because that small size is necessary for our existence. He said that the question of low-energy supersymmetry is something that Douglas’s statistical analysis of vacua should address (Douglas will talk tomorrow), but his view is that low-energy supersymmetry will be very unlikely.

In the question session, John Schwarz challenged him about this, claiming that there were other reasons to believe in low-energy supersymmetry, including the unification of coupling constants and the idea that dark matter is the lowest mass superpartner. Susskind’s response was that even though there were a couple reasons like those, there were many more that indicated problems with the idea of low-energy supersymmetry, including problems with too fast proton decay.

It was pretty amazing to see someone challenging the supersymmetry orthodoxy. On the other hand, the whole program Susskind and others are pursuing is completely loony. String theory predicts absolutely nothing, and instead of drawing the obvious conclusion that it is a useless idea, Susskind is trying to turn this failure into some perverse sort of virtue.

Update: In Michael Douglas’s talk today he said that his calculations show no reason for a low-energy supersymmetry breaking scale to be especially likely. So he expects that supersymmetry will only be broken at a high energy. Maybe somebody should tell the people working on the LHC experiments that the whole supersymmetry thing is now off, they should find something else to look for.

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### 6 Responses to The Landscape at Davis

1. The Landscape at Davis

“I’m in Nothern California this week, and have been attending some of the talks at the conference at UC Davis celebrating Albert Schwarz’s 70th birthday. The landscape at Davis is exceedingly flat, but this morning Lenny Susskind gave a remarkable talk with the title “Exploring the Landscape”.

It was a pretty strange talk for a mathematical physics conference since it contained zero mathematics (and it’s arguable whether there was any physics…). Susskind blamed Iz Singer for this, claiming that Singer told him he should talk about the landscape stuff since it was leading to a new mathematical field of “statistical topology”. He began by holding up a copy of Steven Weinberg’s “Dreams of a Final Theory” and reading a quote from it about the cosmological constant. He liked this so much he read the same quote a second time a little while later.

He then discussed some of the recent history of string theory, noting that for a long time string theorists were hoping for a mathematical silver bullet that would provide a more or less unique solution to the theory that looked like the real world. He announced that now the probability of this is less than 1 in 10^500.

Susskind then explained a bit about KKLT vacua, saying that his main reason for discussing them was to show how silly and inelegant they are. He compared them to a Rube Goldberg machine and called Shamit Kachru the “master Rube Goldberg architect”.

The most dramatic part of Susskind’s talk was something new: an attack on the idea of low-energy supersymmetry. He explained the standard fine-tuning argument for supersymmetry, but then indicated that he thought an anthropic argument made more sense. The reason the Higgs mass is so much smaller than the Planck mass is not supersymmetry, but instead because that small size is necessary for our existence. He said that the question of low-energy supersymmetry is something that Douglas’s statistical analysis of vacua should address (Douglas will talk tomorrow), but his view is that low-energy supersymmetry will be very unlikely.”

[Sarfatti Commentary: According to Lenny’s world hologram idea, the effective Planck scale Lp* should be increasing as the universe expands with scale factor R(t) in units of length as

Lp*(t) = Lp^2/3R(t)^1/3

This means that time’s arrow is tied to the expansion of the universe with the Hawking hologram entropy of the universe S(t) obeying

S(t)/k ~ R(t)^2/Lp*^2 ~ R(t)^4/3

On the other hand, the effective G* from

Lp*^2 = hG*/c^3

cannot operate on the large scale where we know G is Newton’s.

Note that Lp*(now) ~ 1 fermi

This is very curious, making G* ~ 10^40G, which we can posit to act only on the scale of Lp*.

Note also that Lp** = Lp^2/3(c/Ho)^1/3 is also ~ 1 fermi

Einstein’s cosmological constant is /\ ~ (Ho/c)^2

where

/\ = (Lp*)^-2[(Lp*^3|Vacuum Coherence|^2 – 1]

H = R(t)^-1dR(t)/dt

Lp* ~ R(t)^1/3

So we seem to get a differential equation in this model. However, Vacuum Coherence also has a dynamics. It has a covariant Landau-Ginzburg eq with a Mexican Hat Potential for spontaneous broken vacuum symmetry.

So the idea is still not coherent in my mind, but it seems to be pointing to something important.]

“In the question session, John Schwarz challenged him about this, claiming that there were other reasons to believe in low-energy supersymmetry, including the unification of coupling constants and the idea that dark matter is the lowest mass superpartner.”

[Sarfatti Commentary: This is a wrong idea. Dark matter is exotic vacuum with positive zero point pressure. Dark matter detectors will never click in principle with the “Right Stuff” to explain Omega(DM) ~ 0.23. So far observation is on my side in this hard exact prediction. The Italian claims to contrary have proved wrong. So far, so good.]

“Susskind’s response was that even though there were a couple reasons like those, there were many more that indicated problems with the idea of low-energy supersymmetry, including problems with too fast proton decay.”

[Sarfatti Commentary: Susskind is on right track here.]

“It was pretty amazing to see someone challenging the supersymmetry orthodoxy. On the other hand, the whole program Susskind and others are pursuing is completely loony.”

[Sarfatti Commentary: But is it loony enough to be true?]

“String theory predicts absolutely nothing, and instead of drawing the obvious conclusion that it is a useless idea, Susskind is trying to turn this failure into some perverse sort of virtue.”

[Sarfatti Commentary: Indeed string theory has much less observational support than

1. Flying saucers

2. Parapsychology

3. Cold Fusion

It probably has as much observational support as does Ashtekar’s non-perturbative background independent quantum gravity?

I do think however that all of the above have some interesting ideas and factual support that will survive – even sting theory, oh pardon me, I meant even string theory. ;-)]

http://www.math.columbia.edu/~woit/blog/archives/2004_05.html

On Jun 19, 2004, at 5:43 PM, Doc Savage wrote:

bcc

Isn’t Brian Greene a member of Professor Woit’s Department? You mean the landscape is not elegant? Kidding aside, I think Lenny’s work is not as bad as it is made out to be below. “Sting Theory” may be a more appropriate name after all? 🙂

Lenny’s holographic universe idea may turn out to be true. It is certainly very interesting.

The generalized uncertainty relation is also interesting

uncertainty in position ~ h/(uncertainty in momentum) + (quantum of area)(uncertainty in momentum)/h

is a good idea coming from black hole formation when too much energy is concentrated into too small a volume.

On Jun 19, 2004, at 9:58 AM, Doc Savage wrote:

More Landscape Stream of Consciousness

It looks like particle theory has now degenerated to the point where its leading figures can’t think of anything better to do than to write rambling articles with virtually no equations that reach no real conclusions. Last week was Lenny Susskind, tonight there’s a new article by Michael Douglas.

His conclusion, such as it is, goes like this:

“If I had to bet at the moment, I would still bet that string theory favors the low scale, for the reasons outlined above, but it is not at all obvious that this is what will come out in the end…. We should keep in mind that ‘favoring’ one type of vacuum or mechanism over another is not a strong result, if both types of vacuums exist…”

So, maybe string theory “favors” a low supersymmetry-breaking scale, maybe not. As usual, not only can’t it predict anything, it can’t even predict the scale at which it can’t predict anything. I really cannot understand why anyone thinks this kind of thing is science.”

http://www.math.columbia.edu/~woit/blog/archives/000031.html

The stupendous Landscape of sting theory vacua

“At an early stage in the Los Alamos preprint archive it was split up into hep-th (for more formal or speculative work not directly relevant to experiment) and hep-ph (for “phenomenological” papers directly related to experiment). Susskind has just come out with his latest and now seems to feel that his ideas about the “Landscape” are directly of interest to experimenters and so belong in hep-ph.

The preprint is riddled with typos, for instance the third paragraph starts like this:

“During the last couple of years an entirely new paradigm has emerged from the ashes of a more traditional view of string theory. The basis of the new paradigm is the stupendous Landscape of sting [sic] theory vacua — especially the non-supersymmetric vacua. These vacua appear to be so numerous that the word Discrtuum [sic] is used to describe the spectrum of possible values of the cosmological constant…..”

You get the idea.

Some high points of the article:

1. “low energy supersymmetry – an ugly solution” to the naturalness problem. Now he tells us. From what I remember the “beauty of supersymmetry” has always been one argument made in its favor.

2. “the ashes of a more traditional view of string theory”. It seems that the picture of the world according to string theory that has been heavily sold for the last twenty years has burned down to the ground.

3. The argument in his last paper, such as it was, was wrong. Now he’s got a new one with a similar conclusion.

4. “… a prediction that supersymmetry will not be seen at the TEV scale seems warranted”. OK, string theory is finally making a prediction.

5. “If it turns out that low energy supersymmetry is a feature of TEV physics, then we will have to conclude that other considerations outweigh the counting of vacua on the Landscape”. So, even though string theory predicts no low energy supersymmetry, if it is found it doesn’t mean string theory is wrong. Got it?”

http://www.math.columbia.edu/~woit/blog/archives/2004_06.html

2. Peter says:

Hi Thomas,
I saw that paper last night and it is pretty amazing. It attacks the central idea of the whole supersymmetry/string theory ideology. I’ll write something about it in the weblog later today.

The anthropic virus has evidently hit Harvard.

hep-th/0405159
Title: Supersymmetric Unification Without Low Energy Supersymmetry And Signatures for Fine-Tuning at the LHC
Authors: Nima Arkani-Hamed, Savas Dimopoulos

4. Peter says:

I’ve tried to get some action on the Kaku/Horgan bet from string theorists, with no success. They don’t seem to be willing to put their money where their mouth is (actually they increasingly seem unwilling to put their mouth there either: Horgan had trouble finding someone to bet against him and most string theorists are now unwilling to make any guess as to when string theory will ever predict anything).

Rube Goldberg was a cartoonist who drew cartoons of absurd complicated devices that accomplished something very simple. He seems to have fallen out of favor, these things were well-known (at least in the US) during the 60s. For an example, see

http://www.rube-goldberg.com/html/pencil_sharpener.htm

No, Susskind didn’t discover branes, that’s generally attributed to Polchinski. Susskind was one of the co-discoverers of string theory: he and a couple others realized that the Veneziano amplitude could be derived from quantizing a string.

Susskind isn’t necessarily giving up on supersymmetry, just the idea that it will appear at accessible energies. One argument for supersymmetry at LHC energies has always been that you could then explain why the electroweak breaking scale was so much lower than the Planck mass without “fine-tuning”. Susskind’s argument is that one shouldn’t worry about fine-tuning, just figure out what parameter ranges are consistent with human existence, and if there is a uniform distribution of string vacua with those scales, then any one is as good as any other. If so, it is very unlikely that supersymmetry breaking will happen at LHC energies, more likely it will be at very high energies near the Planck or string scale.

5. erinj says:

Well, if Lenny’s right about that probability – and I hope he is – then Michio Kaku’s bet on LongBets.org is almost certainly scuppered! Loser!

I mention Kaku’s bet as I first mistook your report of Susskind’s remark about Kachru as being one about Kaku, who I then remembered has made a long bet involving string theory at LongBets.org… ever tempted to place a bet there, Peter? Increasingly, the reports in your April 1st post look like they may yet come true!

But back to your post: I once saw a talk by Susskind and I was amazed that so many field theorists came out of his talk seemingly convinced of the validity of string theory. Like the talk you saw, I found his equally repetitive and with minimal mathematical (and physical) content.

Wasn’t Susskind the guy who introduced (or, less likely, discovered’) branes? If so, I think him guilty of prolonging the atrocious waste of effort and time that string theory has and had already inflicted upon theoretical high energy physics.

Just what is all this anthropic nonsense, too? String theory is correct because we are here, and because we have discovered’ string theory? Loony all right.

I agree that to see a proponent of superstring theory, and not just string theory (as don’t string theorists dislike working on plain old string theory, given how many extra dimensions and other complications string theory without supersymmetry brings with it?), loosing faith in supersymmetry is suprising. Where would matter fields in string theory be without the simplifying axiom of supersymmetry? As far as I know, all those elaborate intersecting brane theories in which the Standard Model supposedly appears depend upon SUSY at higher energies neatly tying things together.

Also, shouldn’t string theorist’s listen to the experimentalists? (Not more, but in the first place, I mean 🙂

About two years ago I saw a talk by an experimentalist working on some DESY experiment involving a search for `low-energy SUSY’, and he stated that their results permitted them to categorically rule out the lightest possible SUSY superpartner, the higgsino, at the present highest energies attainable (though perhaps a heavy Higgs or something might rescue this). So even back then low-energy SUSY looked unlikely, according to the people who actually go out there and look for these things. I certainly came out of that talk with much less belief in SUSY.

By the way, who or what is “Rube Goldberg”?