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1. • CommentRowNumber1.
   • CommentAuthorUrs
   • CommentTimeFeb 10th 2018
   • (edited Feb 10th 2018)
   • PermaLink
   Author: Urs
   Format: MarkdownItexI have been adding and editing a bit at _[[axion]]_ in the section _[In string theory](https://ncatlab.org/nlab/show/axion#AsArisingFromStringTheory)_. The axion fields in string theory form a curious confluence point relating * abstract concepts related to higher gauge theory with * fundamental questions in particle physics/cosmology phenomenology as indicated schematically in this table (now also in the entry): $\,$ $$ \array{ \mathbf{\text{higher gauge theory}} && && \mathbf{\text{particle physics/cosmology phenomenology}} \\ \\ \left. \array{ \text{higher gauge fields} \\ \text{higher characteristic classes} \\ \updownarrow \\ \text{non-perturbative QFT/string effects} \\ \text{in HET: Green-Schwarz anomaly cancellation} \\ \text{in IIA/B: higher WZW term for Green-Scharz D-branes} } \right\} &\longrightarrow& \array{ \text{axion fields} \\ \text{in the string spectrum} } &\longrightarrow& \left\{ \array{ \text{solve strong CP-problem as with P-Q robustly} \\ \text{solve dark matter problem by FDM} } \right. } $$ $\,$ I will be trying to expand on this a little more.

   I have been adding and editing a bit at axion in the section In string theory.

   The axion fields in string theory form a curious confluence point relating

   • abstract concepts related to higher gauge theory

   with

   • fundamental questions in particle physics/cosmology phenomenology

   as indicated schematically in this table (now also in the entry):

   $\,$

   $$\array{ \mathbf{\text{higher gauge theory}} && && \mathbf{\text{particle physics/cosmology phenomenology}} \\ \\ \left. \array{ \text{higher gauge fields} \\ \text{higher characteristic classes} \\ \updownarrow \\ \text{non-perturbative QFT/string effects} \\ \text{in HET: Green-Schwarz anomaly cancellation} \\ \text{in IIA/B: higher WZW term for Green-Scharz D-branes} } \right\} &\longrightarrow& \array{ \text{axion fields} \\ \text{in the string spectrum} } &\longrightarrow& \left\{ \array{ \text{solve strong CP-problem as with P-Q robustly} \\ \text{solve dark matter problem by FDM} } \right. }$$

   $\,$

   I will be trying to expand on this a little more.

2. • CommentRowNumber2.
   • CommentAuthorDavid_Corfield
   • CommentTimeFeb 11th 2018
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   Author: David_Corfield
   Format: MarkdownItexOn the page, the second line on the right "solve dark matter problem by FDM" isn't appearing for me. Is it due to that URL you included?

   On the page, the second line on the right “solve dark matter problem by FDM” isn’t appearing for me. Is it due to that URL you included?

3. • CommentRowNumber3.
   • CommentAuthorDavid_Corfield
   • CommentTimeFeb 11th 2018
   • PermaLink
   Author: David_Corfield
   Format: MarkdownItexI just look the the Wilczek's talk ([pdf](http://frankwilczek.com/2017/axion_searches_01.pdf)) and added a link to some slides on the 'ABRACADABRA' approach to detection. Is the observational and string theoretic work connected in any way, so that were axions ever detected then parameter values could be explained string theoretically, or is it more that whatever the parameter values, axions arise elegantly out of string theory?

   I just look the the Wilczek’s talk (pdf) and added a link to some slides on the ’ABRACADABRA’ approach to detection.

   Is the observational and string theoretic work connected in any way, so that were axions ever detected then parameter values could be explained string theoretically, or is it more that whatever the parameter values, axions arise elegantly out of string theory?

4. • CommentRowNumber4.
   • CommentAuthorUrs
   • CommentTimeFeb 11th 2018
   • PermaLink
   Author: Urs
   Format: MarkdownItex> isn’t appearing for me. Is it due to that URL you included? Thanks for the alert. I removed the hyperlink. Does it work for you now? Was there a robust way to have hyperlinks inside a maths environment?

   isn’t appearing for me. Is it due to that URL you included?

   Thanks for the alert. I removed the hyperlink. Does it work for you now?

   Was there a robust way to have hyperlinks inside a maths environment?

5. • CommentRowNumber5.
   • CommentAuthorUrs
   • CommentTimeFeb 11th 2018
   • PermaLink
   Author: Urs
   Format: MarkdownItex> Is the observational and string theoretic work connected in any way, so that were axions ever detected then parameter values could be explained string theoretically, or is it more that whatever the parameter values, axions arise elegantly out of string theory? Rather the latter. It's a long long shot, as it goes with these things. But the striking fact, rarely amplified, is the converse: While the string moduli fields may be "stabilized", thus removed from the physically observable spectrum, the string axion fields are present at tiny masses. So axions is a real string signature

   Is the observational and string theoretic work connected in any way, so that were axions ever detected then parameter values could be explained string theoretically, or is it more that whatever the parameter values, axions arise elegantly out of string theory?

   Rather the latter. It’s a long long shot, as it goes with these things.

   But the striking fact, rarely amplified, is the converse: While the string moduli fields may be “stabilized”, thus removed from the physically observable spectrum, the string axion fields are present at tiny masses. So axions is a real string signature

6. • CommentRowNumber6.
   • CommentAuthorDavid_Corfield
   • CommentTimeFeb 11th 2018
   • PermaLink
   Author: David_Corfield
   Format: MarkdownItexYes that's fine without the hyperlink.

   Yes that’s fine without the hyperlink.

7. • CommentRowNumber7.
   • CommentAuthorUrs
   • CommentTimeFeb 11th 2018
   • (edited Feb 11th 2018)
   • PermaLink
   Author: Urs
   Format: MarkdownItexI have added some references [here](https://ncatlab.org/nlab/show/axion#ReferencesExperimentalSignatureInParticlePhysics) on experimental signatures/constraints of axion effects on $(g_{lep}-2)$ ([[anomalous magnetic moment]] of leptons, added these references also there). I was hoping to find a punchline in this textbook contribution: * Yannis Semertzidis, _Magnetic and Electric Dipole Moments in Storage Rings_, chapter 6 of Markus Kuster, Georg Raffelt, Berta Beltrán (eds.), _Axions: Theory, cosmology, and Experimental Searches_, Lect. Notes Phys. 741 (Springer, Berlin Heidelberg 2008) (<a href="https://doi.org/10.1007/978-3-540-73518-2_2">doi:10.1007/978-3-540-73518-2_2</a>) but, unless I am missing something, that chapter six of this book on axion theory does not contain a word rooted in "axion..." even once.

   I have added some references here on experimental signatures/constraints of axion effects on $(g_{lep}-2)$ (anomalous magnetic moment of leptons, added these references also there).

   I was hoping to find a punchline in this textbook contribution:

   • Yannis Semertzidis, Magnetic and Electric Dipole Moments in Storage Rings, chapter 6 of Markus Kuster, Georg Raffelt, Berta Beltrán (eds.), Axions: Theory, cosmology, and Experimental Searches, Lect. Notes Phys. 741 (Springer, Berlin Heidelberg 2008) (doi:10.1007/978-3-540-73518-2_2)

   but, unless I am missing something, that chapter six of this book on axion theory does not contain a word rooted in “axion…” even once.