It seems like there have been a number articles recently talking about the soul searching currently going on in the Physics community over the failure of the LHC to find evidence for super-symmetry (at least so far), a theory that had a lot of theoretical work resting on it. This article discuses that and a new theory: scale symmetry. Radical New Theory Could Kill the Multiverse Hypothesis | Science | WIRED.
Nature, at the deepest level, may not differentiate between scales. With scale symmetry, physicists start with a basic equation that sets forth a massless collection of particles, each a unique confluence of characteristics such as whether it is matter or antimatter and has positive or negative electric charge. As these particles attract and repel one another and the effects of their interactions cascade like dominoes through the calculations, scale symmetry “breaks,” and masses and lengths spontaneously arise.
Similar dynamical effects generate 99 percent of the mass in the visible universe. Protons and neutrons are amalgams — each one a trio of lightweight elementary particles called quarks. The energy used to hold these quarks together gives them a combined mass that is around 100 times more than the sum of the parts. “Most of the mass that we see is generated in this way, so we are interested in seeing if it’s possible to generate all mass in this way,” said Alberto Salvio, a particle physicist at the Autonomous University of Madrid and the co-author of a recent paper on a scale-symmetric theory of nature.
Apparently in this theory, even the Higgs mass arises through dynamic interactions. The article goes into some explanatory detail, much of which I have to admit is above my head. Still, it’s interesting to see the theories that are being dusted off in the wake of the LHC’s findings.
The article discusses how much of this is to avoid falling to the backstop position, the multiverse, which is often posited to explain how various forces and constants in nature happen to be balanced so well for the universe we observe.
As the logical conclusion of prevailing assumptions, the multiverse hypothesis has surged in begrudging popularity in recent years. But the argument feels like a cop-out to many, or at least a huge letdown. A universe shaped by chance cancellations eludes understanding, and the existence of unreachable, alien universes may be impossible to prove. “And it’s pretty unsatisfactory to use the multiverse hypothesis to explain only things we don’t understand,” said Graham Ross, an emeritus professor of theoretical physics at the University of Oxford.
…Picking up where Bardeen left off, researchers like Salvio, Strumia and Lindner now think scale symmetry may be the best hope for explaining the small mass of the Higgs boson. “For me, doing real computations is more interesting than doing philosophy of multiverse,” said Strumia, “even if it is possible that this multiverse could be right.”
I’ve expressed my skepticism before about evoking multiverses to explain the anthropic principle: the idea that our existence is related to constants and parameters that must exist in a narrow range for us to be here. So, I’m happy to hear that many physicists aren’t taking that route, resisting the unfalsifiable explanation until every testable alternative has been ruled out.
I do see multiverses as a candidate for reality, particularly the bubble variety, and there are reasons other than the anthropic principle to suspect that they’re there, but until someone finds a way to test for them, or all of the conceivable testable alternatives are cleared out, I think settling on them as an explanation is premature.