The Landscape at CERN

The current plan at CERN is to celebrate my birthday by trying to circulate the first beam around the LHC on September 10 (actually my birthday is September 11, but in recent years my family, like CERN, has tended to celebrate on the 10th, feeling that 9/11 has too unfortunate connotations). One can follow this at a special web-site set up by CERN called LHC First Beam, which now is running a daily countdown.

String theorists have been flocking to CERN this summer trying to somehow connect their subject with the LHC. The big yearly Strings 08 conference will be starting there next week. The organizers don’t seem to have a lot of sympathy for anthropic pseudo-science, with no talks scheduled on anthropics, the landscape, or the multiverse. Instead they’ll be wisely sticking mostly to talks on topics related to better understanding more formal issues in string theory and quantum field theory.

In the weeks leading up to the conference though, CERN is hosting a theory institute on String Phenomenology. The web-site of the institute has a section on its “Scientific Case”, which, with remarkable chutzpah makes the claim that:

… the past few years have provided a drastic improvement on the potential for string theory models to be confronted with low-energy data

a claim that is diametrically opposed to reality.

For a look at the reality of what the landscape has meant for the “potential for string theory models to be confronted with low-energy data”, one can take a look at the slides of talks by Wati Taylor and Michael Douglas. Taylor describes the importance of distinguishing two possibilities he calls A (anything goes) and B (constraints), and finds in IIA intersecting brane models that the evidence favors A. It seems that such a landscape can give one pretty much any kind of low energy physics, with the things one can compute (the gauge group and number of generations) randomly and independently distributed. He looks for some hope in cosmology, noting that a large class of IIA models are incompatible with slow-roll inflation, while at the same time also pointing out that there are lots of potential ways around this particular constraint, although most of them involve uncontrolled approximations.

Douglas’s talk was entitled String Landscape: A Status Report, and in it he describes evidence for the existence of order 10⁵⁰⁰ “quasi-realistic vacua”. If you don’t impose some constraints from experiment, you’d have an infinite number of possible vacua. He claims that there is no way to rule out any of these vacua, other than to try and compute detailed predictions of each one (something no one has a clue about how to do). Douglas explained why it isn’t possible to make even the crudest prediction that initially he and others had hoped for, that of whether the SSYM breaking scale would be at observable or Planck energies. There’s an odd speculative section about how since SU(2) and SU(3) have shown up on energy scales of 100 MeV to 100 GeV, maybe one gets two new gauge groups for every factor of 1000 in energy (which he calls the “jungle scenario”, as opposed to the conventional “desert scenario”). There’s a final “No Conclusions” section, admitting that “at this point it seems likely that we will not have definite conclusions of predictions before LHC data comes in.” He ends with the standard piece of wishful thinking that now is all that is left of the project of connecting string theory unification models with physics:

Let us hope that discoveries here at Cern will reveal enough about the real world to make contact [with string theory] possible.

Yesterday there was a discussion session on “the string theory landscape and its impact on particle physics and cosmology”, but it doesn’t appear to be online. I wonder what conclusions the participants reached…

Update: Jester at Resonaances has a posting up about this. His impression of the Vafa et al. recent claims about “F-theory phenomenology” seems to match mine:

For the neutrino physicists the important piece of information is that the neutrinos are Dirac or Majorana and their masses are roughly of the order of what is observed. I heard some sceptics saying that back in the old days phenomenology meant a different thing, but such grumbling should not be taken seriously.