Predicting the composition of dark matter

Shedding new light on dark matter
An artist’s rendition of big bang nucleosynthesis, the early universe period in which protons "p" and neutrons "n" combine to form light elements. The presence of dark matter "χ" changes how much of each element will form. Credit: Cara Giovanetti/New York University

A new analysis by a team of physicists offers an innovative means to predict "cosmological signatures" for models of dark matter.

A team of physicists has developed a method for predicting the composition of dark matter—invisible matter detected only by its on and whose discovery has been long sought by scientists.

Its work, which appears in the journal Physical Review Letters, centers on predicting "cosmological signatures" for models of dark matter with a mass between that of the electron and the proton. Previous methods had predicted similar signatures for simpler models of dark matter. This research establishes new ways to find these signatures in more complex models, which experiments continue to search for, the paper's authors note.

"Experiments that search for dark matter are not the only way to learn more about this mysterious type of matter," says Cara Giovanetti, a Ph.D. student in New York University's Department of Physics and the lead author of the paper.

This visualization of a computer simulation showcases the ‘cosmic web’, the large scale structure of the universe. Each bright knot is an entire galaxy, while the purple filaments show where material exists between the galaxies. To the human eye, only the galaxies would be visible, and this visualization allows us to see the strands of material connecting the galaxies and forming the cosmic web. This visualization is based on a scientific simulation of the growth of structure in the universe. The matter, dark matter, and dark energy in a region of the universe are followed from very early times of the universe through to the present day using the equations of gravity, hydrodynamics, and cosmology. The normal matter has been clipped to show only the densest regions, which are the galaxies, and is shown in white. The dark matter is shown in purple. The size of the simulation is a cube with a side length of 134 megaparsecs (437 million light-years). Credit: Hubblesite; Visualization: Frank Summers, Space Telescope Science Institute; Simulation: Martin White and Lars Hernquist, Harvard University.

"Precision measurements of different parameters of the universe—for example, the amount of helium in the universe, or the temperatures of different particles in the —can also teach us a lot about dark matter," adds Giovanetti, outlining the method described in the Physical Review Letters paper.

In the research, conducted with Hongwan Liu, an NYU postdoctoral fellow, Joshua Ruderman, an associate professor in NYU's Department of Physics, and Princeton physicist Mariangela Lisanti, Giovanetti and her co-authors focused on (BBN)—a process by which light forms of matter, such as helium, hydrogen, and lithium, are created. The presence of invisible dark matter affects how each of these elements will form. Also vital to these phenomena is the (CMB)—, generated by combining electrons and protons, that remained after the universe's formation.

The team sought a means to spot the presence of a specific category of dark matter—that with a mass between that of the electron and the proton—by creating models that took into account both BBN and CMB.

"Such dark matter can modify the abundances of certain elements produced in the early universe and leave an imprint in the cosmic microwave background by modifying how quickly the universe expands," Giovanetti explains.

In its research, the team made predictions of cosmological signatures linked to the presence of certain forms of dark matter. These signatures are the result of dark matter changing the temperatures of different particles or altering how fast the universe expands.

Their results showed that dark matter that is too light will lead to different amounts of light elements than what astrophysical observations see.

"Lighter forms of dark matter might make the universe expand so fast that these elements don't have a chance to form," says Giovanetti, outlining one scenario.

"We learn from our analysis that some models of can't have a mass that's too small, otherwise the would look different from the one we observe," she adds.

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More information: Cara Giovanetti et al, Joint Cosmic Microwave Background and Big Bang Nucleosynthesis Constraints on Light Dark Sectors with Dark Radiation, Physical Review Letters (2022). DOI: 10.1103/PhysRevLett.129.021302
Journal information: Physical Review Letters

Citation: Predicting the composition of dark matter (2022, July 6) retrieved 16 August 2022 from
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