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Is the theoretical justification behind proposing axions sufficiently robust, like, say the Higgs boson prior to its detection, that one should consider the existence of axions as generally accepted (though unconfirmed) physics, or are they more speculative than that?

Dave
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    I'm surprised you regard magnetic monopoles as generally accepted, because I don't think this is the case. – John Rennie Feb 27 '15 at 18:00
  • Removed mention of monopoles -- I thought that the quantization condition and field symmetry arguments were considered compelling. – Dave Feb 27 '15 at 18:02
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    @JohnRennie: Magnetic monopoles are perfectly possible within our current theoretical framework. We would not need to change one bit if they exist. There's just no experimental reason to believe they do. I actually have a question that evolved into a question about indirect indications of monopoles. – ACuriousMind Feb 27 '15 at 18:07
  • @ACuriousMind but it's certainly not the case that most people think they exist – Danu Feb 27 '15 at 18:11
  • @ACuriousMind: to me theoretically possible is not the same as generally accepted. – John Rennie Feb 27 '15 at 18:12
  • @Danu Really? Out of curiosity, has anyone actually conducted some survey amongst researchers? It's not particularly valuable, but it would be interesting to know. – JamalS Feb 27 '15 at 18:16
  • @JohnRennie: I just wanted to point out that monopoles are, unlike the Higgs, not required by the theory to explain already observed things, so their existence is independent of the correctness of the general theory, and hence not really relevant to most people. I believe the same is true for the axion. You are of course correct that most people do not think magnetic monopoles exist. – ACuriousMind Feb 27 '15 at 18:18
  • @JamalS For one, I'm unconvinced that most physicists are theoreticians, and I think there is no good reason for experimentalists to believe that they exist. Furthermore, I personally don't find the arguments all that compelling either, so I doubt even a majority of theoreticians would bet on them existing. But, you're right, I was just pulling that out of my [insert-expletive-here] and perhaps I'm wrong about the majority not believing it. – Danu Feb 27 '15 at 18:19
  • @Danu I'd agree there's no good reason for experimentalists to believe that they exist, but even from a mathematical (physics) perspective they merit research, and they're quite interesting. It would certainly be satisfying if they did exist. PS: I've used that turn of phrase occasionally, though I guess I should use ad hoc or something. – JamalS Feb 27 '15 at 18:23
  • I suppose axions are as bit like the Higgs i.e. if they don't exist then something else must exist that does the same job as Peccei Quinn symmetry. – John Rennie Feb 27 '15 at 18:26
  • @JohnRennie -- that's what I'm trying to get at -- It's my understanding that there might have been "exotic" Higg's, but people basically thought that a Higgs (not necessarily the minimal one) existed. – Dave Feb 27 '15 at 18:34
  • See here for the fun story of why 'axions' are named like that. – Danu Feb 27 '15 at 18:35
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    @Dave: I'd guess that most physicists who expressed a preference are open minded. Axioms are theoretically plausible but have proved experimentally elusive, and the symmetry could be accidental or (make the sign of the cross) anthropic. – John Rennie Feb 27 '15 at 18:53
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    I bet most physicists don't know what axions are. – jinawee Feb 27 '15 at 20:59
  • @JohnRennie: Axiom? Best. Typo. Ever. :) – ACuriousMind Feb 28 '15 at 00:06
  • @ACuriousMind: :-))) – John Rennie Feb 28 '15 at 06:07

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Beliefs have no real place in physics, at least should not have. The proposal of particles not seen comes from the theoretical models in order to complete them. For example the omega minus was predicted more or less exactly from the symmetries of the weak SU(3), and was later found .A more exact prediction than the Higgs.

The Higgs as a particle might not have existed, as a higgs mechanism could be used to the same effect for symmetry breaking without biasing the theory In this sense it was a lucky guess that it existed.

Axions can appear in a theoretical model , but they are necessary only for specific ones, as for example in this supersymmetric model where the supersymmetric partner of of the axion is necessary if dark mass can come out of the model naturally,

Because the light stau is the lightest supersymmetric particle (LSP) in the no-scale MSSM, to preserve R parity, we introduce a non-thermally generated axino as the LSP dark matter candidate.

So what you term "belief" is the degree of necessity for a particular model of nature. The broader the constraints, the more models there exist and "belief" gets lower. Though one of these models may get lucky and fit future data.

anna v
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