Evolution of the universe; will an axion discovery help (Introduction)

by David Turell , Monday, June 07, 2021, 18:10 (1046 days ago) @ David Turell

That is the subject of this paper:

https://phys.org/news/2021-06-axions-fossil-universe.html

"How far back into the Universe's past can we look today? In the electromagnetic spectrum, observations of the Cosmic Microwave Background—commonly referred to as the CMB—allow us to see back almost 14 billion years to when the Universe cooled sufficiently for protons and electrons to combine and form neutral hydrogen. The CMB has taught us an inordinate amount about the evolution of the cosmos, but photons in the CMB were released 400,000 years after the Big Bang making it extremely challenging to learn about the history of the universe prior to this epoch.

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"In their paper, they suggest the possibility of searching for an axion analogue of the CMB, a so-called Cosmic axion Background or CaB.

"While hypothetical, there are many reasons to suspect that the axion could exist in our Universe.

"For one, axions are a generic prediction of string theory, one of today's best hopes for a theory of quantum gravity. The existence of an axion could further help resolve the long standing puzzle of why we have yet to measure an electric dipole moment for the neutron, an issue more formally known as the "Strong CP Problem." More recently, the axion has become a promising candidate for dark matter, and as a consequence researchers are rapidly searching for axion dark-matter.

"In their paper, the researchers point out that as experimentalists develop more sensitive instruments to search for dark matter, they may stumble upon another sign of axions in the form of the CaB. But because the CaB shares similar properties with dark-matter axions, there is a risk the experiments would throw the CaB signal out as noise.

"Finding the CaB at one of these instruments would be a double discovery. Not only would it confirm the existence of the axion, but researchers worldwide would immediately have a new fossil from the early Universe. Depending on how the CaB was produced, researchers could learn about various different aspects of the Universe's evolution never possible before (Figure).

"'What we have proposed is that, by changing the way current experiments analyze data, we may be able to search for left-over axions from the early universe. Then, we might be able to learn about the origin of dark matter, phase transition or inflation at the beginning of the Universe. There are already experimental groups who have shown interest in our proposal, and I hope we can find out something new about the early Universe that wasn't known before," says Murayama.

"'The evolution of the universe can produce axions with a characteristic energy distribution. By detecting the energy density of the universe currently made up of axions, experiments such as MADMAX, HAYSTAC, ADMX, and DMRadio could give us answers to some of the most important puzzles in cosmology, such as, "How hot did our universe get? What is nature of dark matter? Did our universe undergo a period of rapid expansion known as inflation? Was there ever a cosmic phase transition?" says Dror."

Comment: The universe had to evolve just as life did when the universe reached a point of fine-tuning to allow life. dhw with his human brain attempts to question God's reasons for a universe that looks like ours does. It allows him to question God's existence. We may never find all of God's reasons. That doesn't cause Him to disappear, does it?