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Axions: From Heaven to Earth

Periodic Reporting for period 3 - AXION (Axions: From Heaven to Earth)

Reporting period: 2020-09-01 to 2022-02-28

Axions are hypothetical particles originally introduced to understand a strange feature of fundamental physical laws: The fundamental laws look very nearly the same if you run time backward (This feature is called time-reversal symmetry, or simply T). Independent of that consideration, cosmologists have observed a strange and so far mysterious feature of the universe: It appears to contain a very large amount of matter that cannot be accounted for in terms of known particles and fields. This is the so-called "dark matter" problem. There is about six times as much dark matter, by weight, as conventional matter.

Remarkably, axions have just the right properties to provide the dark matter. Specifically, they are produced in the right amount during the big bang, they are almost at rest when produced, and they interact very feebly with conventional matter. This makes a surprising and beautiful connection between fundamental physics and cosmology.

If dark matter is made of axions, the theory of axions predicts that it will be difficult, but perhaps not impossible, to detect. We are developing technologies that might make detection possible.

The theoretical ideas which give us axions also suggest new phenomena – ”axion electrodynamics” and ”emergent axions” – that can be and have been, observed in laboratory experiments in special materials. This may lead to useful developments in advanced electronics.
We have constructed a first generation of prototypes of our metamaterial-based antenna technology and are well into the entering testing phase. We have formed an experimental collaboration - the ALPHA collaboration - with world-leading experts in the relevant experimental technologies, and we have started with the experimental phase.
Working groups in the ALPHA collaboration are presently addressing the issues that arise in bringing the above-mentioned technologies to bear in detail. Those groups have been meeting regularly and presently are finalizing white papers.
A major collaboration meeting is planned for January - February 2022, after which the separate white papers will be assembled into a document that will be submitted for publication.
This document will also provide the blueprint for second-generation prototypes that we estimate will be capable of setting new and cosmologically significant limits (or making discoveries) in a narrow range of parameters and demonstrate the possibility to scale up to mature instruments that will fulfill the promise mentioned above.
Remarkably, careful study has revealed that our early estimates of what our plasma haloscopes can achieve were almost certainly too conservative.