New research from the University of Toronto suggests that the so-called clumpiness problem, which centers on the unexpectedly even distribution of matter on large scales throughout the Universe, may be a sign that dark matter is composed of hypothetical, ultra-light particles called axions.
“If confirmed with future telescope observations and lab experiments, finding axion dark matter would be one of the most significant discoveries of this century,” said Dr. Keir Rogers, an astrophysicist with the Dunlap Institute for Astronomy & Astrophysics at the University of Toronto.
“At the same time, our results suggest an explanation for why the Universe is less clumpy than we thought, an observation that has become increasingly clear over the last decade or so, and currently leaves our theory of the Universe uncertain.”
A leading theory proposes that dark matter is made of axions, described in quantum mechanics as fuzzy due to their wave-like behavior.
Unlike discrete point-like particles, axions can have wavelengths larger than entire galaxies.
This fuzziness influences the formation and distribution of dark matter, potentially explaining why the Universe is less clumpy than predicted in the Universe without axions.
This lack of clumpiness has been observed in large galaxy surveys, challenging the other prevailing theory that dark matter consists only of heavy, weakly interacting sub-atomic particles called WIMPs.
Despite experiments like the Large Hadron Collider, no evidence supporting the existence of WIMPs has been found.
“In science, it’s when ideas break down that new discoveries are made and age-old problems are solved,” Dr. Rogers said.
For the study, Dr. Rogers and colleagues analyzed observations of relic light from the Big Bang, known as the Cosmic Microwave Background (CMB), obtained from the Planck 2018, Atacama Cosmology Telescope and South Pole Telescope surveys.
They compared these CMB data with galaxy clustering data from the Baryon…
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