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Axions: From Heaven to Earth

Periodic Reporting for period 2 - AXION (Axions: From Heaven to Earth)

Reporting period: 2019-03-01 to 2020-08-31

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 backwards (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.