## Saturday, August 06, 2005

### Anthropic principle lacks confidence

It is somewhat surprising to obtain the hottest news about the opinions in the string theory community from leading U.S. newspapers. But that's exactly what Dennis Overbye has achieved in his highly penetrating article

The Reference Frame has predicted in May that the panel discussion about the next superstring revolution would be one of the most interesting moments of the Strings 2005 conference. (However, let's admit that the causal relation between the prediction and the NYT article may be slightly different than you think.)

What did various people say during the panel discussion in Toronto four weeks ago? Andy Strominger was very upbeat; something that Joe Marsano has been explaining to me, too. He criticized those of us who spread the atmosphere of pessimism. He informed everyone that soon or later, the string theorists will find the right explanations and all of them will be celebrated as heroes; there are no obstacles in principle to solve all of our current problems. Not everyone has to join the efforts to complete string theory; for example, the stupid people and the people focusing on other parts of physics won't do it. ;-)

Some people in the audience, notably Lee Smolin, have even questioned whether the string theorists will be celebrated as heroes and he insisted that the background independence was more paramount. That's like screaming that God is dead in the church during the mass, and Lee gets points for his courage. ;-)

Steve Shenker, the moderator of the discussion, and essentially also Edward Witten warned everyone that the new revolutions are likely to emerge from ideas that are underestimated by the community. They found it likely that some of the most important recent advances could not have been predicted in these general discussions. A similar reason has also led Steve Shenker to include several young people into his panel.

Jacques Distler was much more disgusted by this general discussion and he followed the example of Nancy Hopkins and left the room, saying that no other field of science would be so presumptuous to talk about its next revolution. Dennis Overbye correctly points out that string theory is not exactly just "another field of science".

Obviously, the most striking and controversial of the known current ideas of this kind seems to be the revived anthropic principle. Overbye describes the "war on the landscape" - which has been recently renamed by my friends in the White House to a "global struggle against the violent anthropic extremism" in order to emphasize that the soldiers are not the only ones involved in this important struggle - as a conflict between Stanford (Al Qaeda) and Princeton (Coalition of the Willing) or the West Coast vs. the East Coast. (Harvard is mixed.)

The anthropic principle argues that the vacuum is selected more or less randomly and we should not be really looking for the rules that determine the right one; the existence of potentially intelligent structures such as galaxies and humans is supposed to provide us with the only extra selection criterion. In other words, the anthropic principle wants to replace fundamental physics and quantitative statements as the explanation of the properties of the Universe by a popular vote where it is the people who are in charge; it wants to replace science by democratic politics.

In democracy, one should ask: So what do the people think about the anthropic principle? The panelists were evenly split: 4 vs. 4. What about the audience?

• An overwhelming majority of the audience have supported the resolution that the anthropic principle lacks confidence.

Note that it is a "lack of confidence", not "no confidence", and therefore it will still be allowed to submit articles that openly endorse the anthropic thinking. On the other hand, the anthropic people should now feel depressed because the scientifically and politically correct majority does not like their principle. If the March 15th FAS vote is a good example, we, the anti-anthropic people, should now also be allowed to humiliate the anthropic people ad hominem (or at least ad anthropos) and demand an unlimited number of anti-anthropic committees to be established.

Because the anthropic principle wants to introduce democracy to physics, it follows from the vote that the anthropic principle is either wrong or internally inconsistent. ;-) When the results of the vote were announced, a panelist said:

• "Wow!"

while another anthropic panelist screamed something like

• "Fucking holy NS-NS shit!"

This assertion was probably too colorful for the black-and-white printing of the New York Times. My blog has no problems with it because it is colorful.

• "The anthropic principle is out of office."

Mike Douglas seemed to be doing fine with the lack of experimental input: "We've been doing very well without it in the last 20 years." Nima, on the other hand, emphasized how much new and exciting data the LHC can bring us. He described the LHC Olympics and the punch line that it may turn out to be very difficult to isolate a particular supersymmetric (or non-supersymmetric) model that will fit the LHC data with the available accuracy.

Nima often says that the discovery of supersymmetry would not help the string theorists to solve the truly deep questions. Well, maybe there are better scenarios - but I would still prefer SUSY to be discovered by the LHC to get a confirmation that we are on the right track. Once we know the structure of superpartner masses, we will have a better idea how SUSY is broken. This may allow us to identify more realistic stringy models; either the conventional or the braneworld models would almost definitely get an advantage. Such data may indirectly tell us about the vacuum selection mechanisms, I think.

The pheno guys at Harvard have been explaining me (and us) how degenerate various SUSY models can be in their predictions; many Harvard computers were recently working on the identification of the right models that match some fictitious data from the LHC and the results were usually ambiguous. In many cases it is difficult to determine the spin (and even the spin modulo 1, i.e. the statistics) of a new particle you observe, and so on.

What did Lenny Susskind, the inventor of string theory and the landscape, think about these issues today? What's his most important issue today?

• "There's nothing to do but just hope the Bush administration will keep paying us."

That's a very interesting opinion, Lenny. If this is the main goal, Lenny may want to change his strategy and try to prove that his stringy landscape is equivalent to Intelligent Design after all instead of talking about illusions. ;-) Nati Seiberg did not endorse the anthropic principle but he had to emphasize that despite his conservatism, he is coming from a blue state. Amanda Peet proposed to transform string theory into a "faith-based initiative" and the laughter that followed was nervous. Joe Polchinski argued that the "next" revolution has already occured 5 years ago - this probably means the moment when he and Raphael Bousso proposed the discretuum, later upgraded to a landscape by Lenny Susskind.

However, the 1984 revolutionary Michael Green argued that even if the anthropic explanation of the cosmological constant problem were correct, it could not spark the third superstring revolution because if the problem were decided in such a willy-nilly fashion, it would prove that the cosmological constant problem was not an important part of fundamental physics anyway.

At any rate, according to the electronic version of the New York Times, the predicted C.C. is just 1060 times bigger than the observed one - and the remaining three orders of magnitude are not such a bad hierarchy problem after all. :-) (To be sure: I suppose that the number "60" was an exponent and this large number expresses the cosmological constant in SUSY models broken at a TeV.)

Also, I was explained that Mike Green thinks that physics of the "wrong" vacua will become more or less irrelevant for conventional physics (as opposed to quantitative philosophy) once the correct vacuum is found. We already know that there exist theories that do not describe the real world - such as the Ising Model - and we should not be worried about their existence. While I agree with Green, needless to say, the anthropic people typically disagree. I think that if we identify the right vacuum during a sunny day in the future, it will become by far the most interesting vacuum to study. The other vacua will turn into curiosities and only physicists with philosophical and science-fiction tendencies will find them interesting enough to be studied. (Yes, I have these tendencies, too. Even if we knew exactly which vacuum describes the world around - if we found it essentially by chance - it would be interesting for me to look whether it differs from others in some essential way; moreover, the physics of other vacua could still be equally mathematically interesting as the physics of our vacuum.)

Steve Shenker, an authority that is claimed to be scary for many colleagues for reasons that I don't fully understand, concluded that we had made some progress in sharing our feelings.