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posted by martyb on Saturday June 27 2020, @10:56AM   Printer-friendly
from the what's-the-matter? dept.

Case for axion origin of dark matter gains traction:

The existence of dark matter has been confirmed by several independent observations, but its true identity remains a mystery. According to this study, axion velocity provides a key insight into the dark matter puzzle. Previous research efforts have successfully accounted for the abundance of dark matter in the universe; however certain factors, such as the underproduction of axions with stronger ordinary matter interactions, remained unexplored.

By assigning a nonzero initial velocity to the axion field, the team discovered a mechanism—termed kinetic misalignment—producing far more axions in the early universe than conventional mechanisms. The motion, generated by breaking of the axion shift symmetry, significantly modifies the conventional computation of the axion dark matter abundance. Additionally, these dynamics allow axion dark matter to react more strongly with ordinary matter, exceeding the prediction of the conventional misalignment mechanism.

"The extensive literature on the axion was built upon the assumption that the axion field is initially static in the early universe," stated Keisuke Harigaya of the Institute for Advanced Study. "Instead, we discovered that the axion field may be initially dynamic as a consequence of theories of quantum gravity with axions."

Journal Reference:
Raymond T. Co, Lawrence J. Hall, Keisuke Harigaya. Axion Kinetic Misalignment Mechanism [open], Physical Review Letters (DOI: 10.1103/PhysRevLett.124.251802)


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  • (Score: 4, Informative) by zocalo on Saturday June 27 2020, @12:47PM

    by zocalo (302) on Saturday June 27 2020, @12:47PM (#1013220)
    Gravitational effects on nearby stars? We can't directly detect many blackholes, yet we know they are almost certainly there because a large mass causes detectable changes to the orbits of stars within the local stellar neighbourhood. Even a long dead dwarf star that has cooled to the point it is undetectable from the background noise (and I'm not sure if the universe is old enough for there to be all that many of those yet - pressure generates heat, and even a stellar remnant is going to have a warm core for a *long* time) is going to have quite a bit of mass in a relatively small volume.

    Dark Matter, is generally thought of as a more diffuse distribution of mass - dust, gas, atomic particules - that we are currently unable to identify beause it's not emitting or reflecting enough light/energy for us to detect, but being distributed over a much larger area. We think of stars as large objects, but space is still almost entirely empty; if you distribute a stellar mass with the typical density of a stellar dust or gas cloud, it's going to occupy a volume that measures light years on a side. Same overall mass, but much less likely to have an appreciable impact of a stellar orbit, let alone one that we can detect.
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