## Tuesday, February 08, 2011

### Do you think inflation probably happened? A poll

Sean Carroll asked his readers to quantify their confidence that various physical explanations or theories are right.

The TRF readers don't have to be explained that polls don't mean anything in science, and I actually expect most of the answers to be bogus.

With all my immense respect to the body of all readers, I would expect the average percentages to be bogus even among the readers of this blog who are exceptionally educated and well-informed.

Nevertheless, the entries to be rated are:
1. Cosmic inflation
2. Supersymmetry
3. String theory
4. Higgs boson of any type
5. Large extra dimensions
6. WIMP dark matter
7. Explanations of accelerated expansion not based on the cosmological constant

If you decide to offer your numbers, be honest. I don't plan any discimination.

If you want to know how your humble correspondent will adjust his idea about your knowledge of physics, well, obviously, the closer you get to my answers, the better. ;-) However, you should avoid copying the figures because your results could become too obviously fabricated. ;-)

My answers, mostly covered in a 2007 article together with others, are
1. 90%
2. 70% (60% at the LHC)
3. 85% (will be vital in hep-ph; 99.95% for consistency)
4. 99.5% (at the LHC)
5. 1% (found by 2020)
6. 85% (90% more general models of dark matter)
7. 3%
There's some very limited room for alternative theories that could replace inflation, and the need for inflation somewhat depends on our intuition and principles that are broad. However, the 10% for non-inflation still includes some hypothetical models that could be called "generalized inflation".

Supersymmetric should exist below the Planck scale, e.g. the GUT scale, and probably below it. It's very natural for supersymmetry to survive up to a TeV scale, so the LHC should ultimately see it.

String theory is pretty much unquestionably a consistent quantum theory of gravity and other forces and particles, the only one we are familiar with at this moment, and arguably the only one that is mathematically possible. So even the question whether it has to be right is answered by a pretty resounding Yes. Whether those facts will ever be transformed to "completely practical applications", i.e. string theory's being a crucial improvement of quantum field theory for observable particle physics (producing predictions of doable experiments that simply can't be obtained from QFT) remains somewhat unknown and I rated it 85%.

A Higgs boson is necessary to restore the unitarity of the WW-to-WW scattering. Some bounds indicate that it has to exist. It is actually almost guaranteed that the lightest Higgs boson sits below 200 GeV. Somewhat paradoxically, the LHC will have a hard time to find it if its mass is close to the LEP lower bound around 115 GeV - which I find "unexpectedly" likely (close to 50%).

Large extra dimensions get 1% from me and warped extra dimensions would get 2%. I mean large enough or warped but flat enough to be visible at the LHC at some point. These ideas are conceivable at the phenomenological level but somewhat unnatural from the high-energy perspective. The relevant compactifications of string theory look awkward. It seems much more likely that this crucial stuff - e.g. extra dimensions - is hiding near the fundamental scale which corresponds to much higher energies.

The cosmological models including the dark matter work very well and the dark matter seems to be irreplaceable and in some sense, it has been almost directly seen. There is incomplete but strong evidence that dark matter is dominated by cold dark matter and WIMP seems like by far the most well-motivated version of cold dark matter, especially because supersymmetry gives a natural candidate for the WIMP particle. So WIMP gets 85% from me.

Alternative explanations of the accelerated expansions get 3% from me. The positive cosmological constant is annoying and I still think it's not "quite" excluded that the cosmological constant is strictly zero and the acceleration is due to "something else". The "something else" would face hard tests to agree with the observational data, but it would bring some relief to the theory, especially the revived possibility that the anthropic reasoning is not needed to explain similar parameters of the low-energy world. At any rate, non-C.C. explanations of the accelerated expansion get 3% from me.