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As you read this story, you will learn the following:
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When analyzing data from the early universe, the Standard Model of Cosmology suggests that the universe should be “bumpier” than we observe.
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A new study suggests that interactions between two of the most elusive particle types in the universe – dark matter and neutrinos – may help explain the discrepancy.
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The study analyzed cosmic shear data from the early and late universe and speculated that the strength of this interaction was about 10-4.
Two of the most mysterious particles in the known universe are dark matter (theoretically made up of most matter in the universe) and neutrinos (weakly interacting, nearly massless subatomic particles that cannot be directly observed). Because both particles are clearly antisocial, the ΛCDM model (our current best guess at what makes the universe work) suggests that they make sense certainly Don’t interact with each other. Correct?
Well, not so fast. A new study by scientists from the University of Sheffield, the Polish National Center for Nuclear Research and the University of Science and Technology of China analyzed cosmic shear data from early and late universe sources and shows that interactions between these two types of particles could explain why the universe is not as lumpy as we might expect from early universe data alone. Results published in journal natural astronomy.
“Observations of the modern universe show that matter is slightly less clumped than expected, suggesting a slight mismatch between early and late measurements,” Eleonora Di Valentino, co-author of the study at the University of Sheffield, said in a press statement. “Our study shows that interactions between dark matter and neutrinos could help explain this difference, providing new insights into how the structure of the universe formed.”
To come to this conclusion, scientists first needed a lot of data from both eras of the universe—and luckily, they had plenty to choose from. For the early universe, they relied on observations from the land-based Atacama Cosmology Telescope and the space-based Planck telescope. For the most recent observations, the team relied on extensive data from the Dark Energy Camera of the Victor M. Blanco Telescope in Chile and the Sloan Digital Sky Survey.
With the available data, Valentino and her team focused on a phenomenon called cosmic shear, which describes the distortion of images of distant galaxies due to weak gravitational lensing caused by the structure of the universe. According to Universe Today, if neutrinos and dark matter interact, the interaction would affect the structure of galaxy clusters and voids in a similar way to what we observe today. According to the team’s observations, the reaction intensity between dark matter and neutrinos is about 10-4.
While this is compelling evidence, the scientists point out that the statistical significance of this finding is 3 sigma (3σ), which is not enough to be considered clear evidence (statistical significance of 5σ is usually required). Valentino also clarified that this discovery does not necessarily overturn the ΛCDM model, but may indicate that it is complete.
Hopefully, future cosmic microwave background experiments, more precise weak lensing surveys, and more accurate data from new telescopes will further confirm (or deny) this big “Wow, if that’s true” moment.
William Giarè, a co-author of the study at the University of Sheffield, said in a press statement: “Not only does it shed new light on the persistent mismatch between different cosmological detectors, but it also gives particle physicists concrete directions on what properties to look for in laboratory experiments to help ultimately uncover the true nature of dark matter.”
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