Physicists Have Developed a Method for Predicting the Composition of Dark Matter

Big Bang Nucleosynthesis

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: Image courtesy of Cara Giovanetti/New York University

A new analysis offers an innovative means to predict ‘cosmological signatures’ for models of dark matter.

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

The new work 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. The paper was published on July 6 in the journal Physical Review Letters.

“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. 

“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 early universe—can also teach us a lot about dark matter,” adds Giovanetti, outlining the method described in the Physical Review Letters paper.

In the research, the physicists focused on big bang nucleosynthesis (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 cosmic microwave background (CMB)—electromagnetic radiation, generated by combining electrons and protons, that remained after the universe’s formation. The work was 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.

The team of scientists 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 their 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 dark matter can’t have a mass that’s too small, otherwise the universe would look different from the one we observe,” she adds.

Reference: “Joint Cosmic Microwave Background and Big Bang Nucleosynthesis Constraints on Light Dark Sectors with Dark Radiation” by Cara Giovanetti, Mariangela Lisanti, Hongwan Liu and Joshua T. Ruderman, 6 July 2022, Physical Review Letters.
DOI: 10.1103/PhysRevLett.129.021302

The research was supported by grants from the National Science Foundation (DGE1839302, PHY-1915409, PHY-1554858, PHY-1607611) and the Department of Energy (DE-SC0007968).

5 Comments on "Physicists Have Developed a Method for Predicting the Composition of Dark Matter"

  1. IMHO, Dark Matter is just a side-effect caused by Dark Energy (which is the real mystery)!
    As an analogy, consider growing/inflating pockets of gas in rising dough!
    (Imagine spacetime as a bubbling/boiling (because of incoming DE!) superfluid!)
    (So the locations in space w/ “lots of DM” are actually just where spacetime superfluid is denser!)
    As for evidence:
    Isn’t it true that geometric structure of Cosmic Web looks really like bubbling (instead of collapsing!)? (So it has positive curvature instead of negative!?)
    Isn’t it true that some galaxies appear to have too much DM & so others too little (contrary to all expectations!)?
    (& not to mention, no experiment/observation is ever able to find any new particle which could be what DM is made of!)

    • Howard Jeffrey Bender, Ph.D. | July 22, 2022 at 10:25 am | Reply

      Interested in Dark Energy, eh? One way to explain it is suggested by String Theory. All matter and energy, including photons (light), have vibrating strings as their basis.

      String and anti-string pairs are speculated to be created in the quantum foam, a roiling energy field suggested by quantum mechanics, and they immediately annihilate each other. If light passes near these string/anti-string annihilations, perhaps some of that annihilation energy is absorbed by the string in the light. Then the Fraunhofer lines in that light will move a bit towards the blue and away from the red shift. As this continues in an expanding universe we get the same curve displayed by Perlmutter and colleagues at their Nobel Prize lecture, without the need for Dark Energy.

      This speculation has the universe behaving in a much more direct way. Specifics on this can be found by searching YouTube for “Dark Energy – a String Theory Way”

  2. Howard Jeffrey Bender, Ph.D. | July 22, 2022 at 10:21 am | Reply

    The speculations in this article are yet another attempt to find what nobody sees. Another possibility, from a view of String Theory, is that Dark Matter appears to us as an effect of string/anti-string annihilations. As you may know, quantum mechanics requires that strings must be formed as pairs in the quantum foam – a string and an anti-string – that immediately annihilate each other. Quantum mechanics also requires both the string and anti-string to be surrounded by “jitters” that reduce their monstrous vibrating energies. What if this jitter remains for a fraction of an instant after their string/anti-string annihilations? This temporary jitter would be seen by us as matter, via E=mc2, for that instant before it too returns to the foam. That’s why we never see it – the “mass” lasts only for that instant but is repeated over and over and over, all over. Specifics on this can be found by searching YouTube for “Dark Matter – A String Theory Way”

  3. Caleigh Fisher | July 22, 2022 at 3:44 pm | Reply

    Dark matter is extremely diffuse amorphous hydrogen. The result of neutron decay in deep voids.
    Neutron decay cosmology is inevitable.
    Neutrons/matter which contacts event horizons becomes the vacuum flux for one single Planck second then reemerges, via a trick of topology, in lowest energy density points of space where it then decays into this amorphous atomic hydrogen. The decay process includes a volume increase of 10^54 times. Lambda. Expansion. Dark energy.
    The decay product, amorphous atomic hydrogen, doesn’t have stable orbital electron so can’t emit or absorb photons. Dark matter. In time the hydrogen stabilizes and follows usual evolution pathway from gas to nebula to proto star to star to neutron star until in distant future it is again at edge of event horizon.
    The universe is steady state evolving locally. A continuous flow down the Ricci curve.
    Neutron decay cosmology.

  4. As always, the answer will be simple,discovered acidentally and obvious for anyone!

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