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.