Tom Banks has a new preprint out, entitled Landskepticism: or Why Effective Potentials Don’t Count String Models. In it he argues against the idea that one can use effective potentials to study the supposed “Landscape” of different vacuum states of superstring theory. His preprint, like most of the literature in the field, is kind of a bizarre document which doesn’t even look like a conventional theoretical physics paper. In the course of twenty pages he only really manages to write down one equation (and it’s just the Schrodinger equation).
One of his claims is that it doesn’t make any sense to think of what is going on as one string theory Hamiltonian with a huge number of possible vacuum states. Instead one has to think of a huge number of possible string theory Hamiltonians, one for each asymptotic background. So I guess that’s it for the “uniqueness of string theory”.
He gets kind of vehement: “the concept of an effective potential on moduli space as a tool for finding string models of gravity, is a snare and a delusion, fostered by wishful thinking, and without regard to the actual evidence in front of us.” Sounds kind of like things I say… He footnotes this “Perhaps some over the top rhetoric is in order”.
On a different topic, he claims that the Weinberg “prediction” of the cosmological constant doesn’t hold water, since if you allow both the cosmological constant and other parameters to vary, then typical values of the cosmological constant allowing galaxy formation will be orders of magnitude larger than the observed value.
I shouldn’t give the impression that Banks is opposed to string theory. Like everyone else, he doesn’t even mention the possibility that it might be wrong. He has his own ideas about holography and cosmological breaking of supersymmetry, which he alludes to at the end.
His paper is based on a talk he gave at a String Vacuum Workshop in Munich three weeks ago. Kind of scary to see how many theorists are now working on this nonsense. At first I was worried to see my old friend and fellow Princeton student Costas Bachas’s name on the list of participants. Costas always seemed to me one of the more sensible theorists around, even if he did work a lot on string theory. Then I noticed that he wasn’t giving a talk, just leading a discussion on the topic “Does the ‘String Vacuum Project’ make sense?” Wonder what their conclusion was.
Update: For Lubos Motl’s take on this paper (Banks was his advisor), and the news that Nima Arkani-Hamed has gone over to the dark side, go here.