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Case for Axion Origin of Dark Matter Gains Traction

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

upstart writes in with an IRC submission:

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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Original Submission

• Re:Dark matter (Score: 3, Interesting) by khallow on Saturday June 27 2020, @12:41PM

  by khallow (3766) on Saturday June 27 2020, @12:41PM (#1013218) Journal

  Gravitational effects are different for diffuse matter versus highly concentrated near-point mass. For example, you'd get some degree of observable gravitational lensing from the detritus of stars (black holes, neutron stars, and white dwarfs) that you wouldn't see with exotic particles. Also there's the issue of transport. A stellar remnant has to come from somewhere where stars were created and they normally don't move very fast relative to that creation point. These exotic particles could be moving from the creation of the universe and would have little connection to galaxies aside from gravity.
  
  For me, the biggest problem with exotic particle dark matter is how do you get it moving slow enough that it can be captured and concentrated by a galaxy? For example, typical neutrinos have many orders of magnitude over the kinetic energy they need to escape from the galaxy and to our knowledge, they don't interact with anything. You couldn't get a cloud of neutrinos distorting galaxy gravitational fields, because they wouldn't stick around.

  Parent

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