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After the multiverse, the… multiworse?

soap bubbles/Timothy Pilgrim

From Sabine Hossenfelder at her blog Back(Re)Action:

It’s a PR disaster that particle physics won’t be able to shake off easily. Before the LHC’s launch in 2008, many theorists expressed themselves confident the collider would produce new particles besides the Higgs boson. That hasn’t happened. And the public isn’t remotely as dumb as many academics wish. They’ll remember next time we come ask for money.

What the particle physicists got wrong was an argument based on a mathematical criterion called “naturalness”. If the laws of nature were “natural” according to this definition, then the LHC should have seen something besides the Higgs. The data analysis isn’t yet completed, but at this point it seems unlikely something more than statistical anomalies will show up.

Naturalness, of course, has always been a criterion in theory-space, which is exactly why I keep saying it’s nonsense: You need a probability distribution to define it and since we only ever observe one point in this theory space, we have no way to ever get empirical evidence about this distribution. So far, however, the theory space was that of quantum field theory.

When it comes to the landscape at least the problem of finding a probability distribution is known (called “the measure problem”), but it’s still unsolvable because we never observe laws of nature other than our own. “Solving” the problem comes down to guessing a probability distribution and then drowning your guess in lots of math. More.

Lost in Math Hossenfelder is one of those theoretical physicists who thinks that science should make sense. Wish her well. So many would just love to slip the bonds of reason…

She is the author of the forthcoming Lost in Math: How Beauty Leads Physics Astray (June, 2018).

The public may be more willing to pony up for Son of LHC than she thinks. As many people here in Canada have pointed out, it costs money but it isn’t nuclear war.

See also: The multiverse is science’s assisted suicide

Are we chasing 'pipe dreams' by extending the power of the LHC? If that's the case, then how do we justify the huge amounts of money needed? Supersymmetry has more or less died with the current LHC results. Until such time as there is some evidence that some new particle will appear at even higher energies, I think we should 'keep our powder dry.' As an apt aside, the move forward in QFT (quantum field theory) that led to the "electro-weak" theory and QCD (quantum chromodynamics, so named because within nucleons [neutrons and protons] there is "color" charge instead of electric charge) came from condensed matter physics. In today's world, these physicists are the ones who are doing the real fundamental research, and I expect that particle physics will only advance when condensed matter physicists finally arrive at very precise measurements. And I think we're on our way. BTW, these experiments pale in cost compared to the LHC. What's needed in the meantime---and it, too is happening, is a rethinking of the fundamentals of already accepted and verified theory. I think this is what Sabine is arguing for. PaV
The Anthropic Principle: Chapter 13 of materialistic cosmology. LocalMinimum
Although Hossenfelder is a convinced evolutionist herself, she offers a telling inside in what today's physicists want and don't want:
I must have sat through hundreds of seminars in which naturalness arguments were repeated. Let me just flash you a representative slide from a 2007 talk by Michelangelo L. Mangano (full pdf here), so you get the idea. The punchline is at the very top: “new particles must appear” in an energy range of about a TeV (ie accessible at the LHC) “to avoid finetuning.” … This was the argument why the LHC should see something new: To avoid finetuning and to preserve naturalness. I explained many times previously why the conclusions based on naturalness were not predictions, but merely pleas for the laws of nature to be pretty. Luckily I no longer have to repeat these warnings, because the data agree that naturalness isn’t a good argument.
“Pretty” as in ‘not-fine-tuned’?
My disbelief in naturalness used to be a fringe opinion and it’s gotten me funny looks on more than one occasion. But the world refused to be as particle physicists expected, naturalness rapidly loses popularity, and now it’s my turn to practice funny looks. The cube, it’s balancing on a tip and nobody knows why. In desparation they throw up their hands and say “anthropic principle”. Then they continue to produce scatter plots. … The naturalness arguments are eventually based on the idea that whatever a fundamental theory looks like, it does conform to this ideal: There's one or only a few parameters. They are neither fine-tuned nor appear in unreasonably large ratios. We, the stuff we are made of, and our universe, is somehow "natural," "average" or "mediocre." However, if you continue to ask "why" at this point you'll notice how the scientific basis crumbles away under your feet. Why should this be? Because very small parameters make you feel uneasy? Because you don't find many parameters a satisfactory explanation? Because it's not pretty? Because it smells like intelligent design?
Despising the greater beauty you have yet to conceive of for the perceived loss of the cheaper beauty you never possessed. LocalMinimum

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