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Axions may be the fossil of the universe that researchers are waiting for

Axions may be the fossil of the universe that researchers are waiting for

The difference in the shape of CaB as a function of energy and density can be seen for four different scenarios for its production. Finding one of them would help answer the main questions listed. Credit: Dror et al.

Finding the hypothetical particle axion could mean finding out for the first time what happened in the universe a second after the Big Bang, a new study published in Physical examination D on June 7.

How far back in the past of the universe can we look today? In the electromagnetic spectrum, observations of the cosmic microwave background ̵

1; commonly called CMB – allow us to see almost 14 billion years ago when the universe cooled enough for protons and electrons to combine to form neutral hydrogen. CMB taught us a great deal about the evolution of space, but the photons in CMB were released 400,000 years after the Big Bang, which made it extremely challenging to learn about the history of the universe before that era.

To open a new window, a trio of theoretical researchers, including the Kavli Institute of Physics and Mathematics of the Universe (Kavli IPMU) Principal Investigator, University of California, Berkeley, MacAdams Professor of Physics and Senior Lecturer at the Lawrence Berkeley National Laboratory Hitoshi Murayama, Researcher from Lawrence Berkeley National Laboratory and the University of California, Berkeley, postdoctoral fellow Jeff Dror (now at the University of California, Santa Cruz) and UC Berkeley Miller researcher Nicholas Rod looked beyond the photons and into the realm of known hypothetical particles that can axions were broadcast in the first second of the history of the universe.

In their report, they offer the possibility of searching for an axion analogue of CMB, the so-called Cosmic Axion Background or CaB.

Although hypothetical, there are many reasons to suspect that the axion may exist in our universe.

On the one hand, axions are a generic prediction of string theory, one of the best hopes for quantum gravity theory today. The existence of an axion can further help solve the long-standing puzzle of why we have not yet measured the electric dipole moment for a neutron, a problem more formally known as the “Strong CP Problem.” More recently, axion has become a promising candidate for dark matter, and as a result, researchers are quickly searching for the darkness of axion.

In their report, the researchers point out that while experimentalists are developing more sensitive tools for searching for dark matter, they may come across another sign of axions in the form of CaB. But because CaB shares similar properties with the axions of dark matter, there is a risk that experiments will throw out the CaB signal as noise.

Finding CaB in one of these tools would be a double discovery. Not only will it confirm the existence of the axion, but researchers around the world will immediately receive a new fossil from the early universe. Depending on how CaB is produced, researchers can learn about various different aspects of the evolution of the universe that were never possible before (Figure).

“What we’ve suggested is that by changing the way current experiments analyze the data, we may be able to look for residual axions from the early universe. Then we may be able to learn about the origin of dark matter, the phase transition, or inflation at the beginning of the universe.” “There are already experimental groups that have shown interest in our proposal, and I hope we can find something new about the early universe that was not known before,” Murayama said.

“The evolution of the universe can produce axions with a characteristic energy distribution. By discovering the energy density of the universe currently composed of axions, experiments such as MADMAX, HAYSTAC, ADMX and DMRadio can give us answers to some of the most important puzzles in cosmology. , such as, “How hot has our universe become? What is the nature of dark matter? Has our universe undergone a period of rapid growth known as inflation? Has there ever been a cosmic phase transition?” says Dror.

The new study gives reason to worry about the axion dark matter program. Even if dark matter is not made of axions, these tools can provide an image of the universe when it has been in less than a second.

This study was accepted as the “Editors’ Proposal” in the journal Physical examination D.

The DALI experiment: Search for the axion, a proposed component of dark matter

More information:
Jeff A. Dror et al., Space background of the action, Physical examination D (2021). DOI: 10.1103 / PhysRevD.103.115004

Provided by the Kavli Institute of Physics and Mathematics of the Universe

Quote: Axions may be the fossil of the universe that researchers are waiting for (2021, June 7), extracted on June 7, 2021 from https://phys.org/news/2021-06-axions-fossil-universe.html

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