May 10, 2024

Dark Matter Could Help Solve the Final Parsec Problem of Black Holes

Simply as the famous three-body problem has no basic analytical service for Newtonian gravity, the two-body issue has no basic option in basic relativity. So, we need to resort to computer system simulations to model how black holes orbit each other and ultimately combine. For binary great voids that are relatively commonly apart, our simulations work truly well, however when great voids are close to each other things get made complex. Einsteins equations are very nonlinear, and modeling the dynamics of strongly communicating black holes is challenging.
One idea to resolve the issue is to introduce dark matter into the mix. Cold dark matter is nearly everywhere according to the basic cosmological design, so it likely plays a role in the mergers of supermassive black holes. So far it seems cold dark matter isnt the answer.
In this brand-new study, the group thinks about a variation on dark matter understood as fuzzy dark matter. Since these particles would not engage with each other by anything other than gravity, they would not clump in quite the same method as routine dark matter, and thus have a more “fuzzy” distribution.
Fuzzy dark matter was first proposed to resolve what is called the cusp problem of dwarf galaxies, which is a powerlessness for dark matter. Here the authors reveal that fuzzy dark matter can increase the rate of orbital decay for black holes, especially the biggest of supermassive black holes. It could explain a few of the monsters weve observed at the heart of some elliptical galaxies.
However the work doesnt prove fuzzy dark matter is the solution. The details of the final stage of inspiralling great voids are still, shall we say, a bit fuzzy. It will take direct observations of supermassive black holes to either prove or rule out the concept. Future NANOGrav observations, or those of the planned LISA gravitational wave observatory ought to be able to see such mergers. Then our understanding of how the biggest great voids in the cosmos merge wont be quite so fuzzy.
Referral: Koo, Hyeonmo, et al. “Final parsec issue of great void mergers and ultralight dark matter.” arXiv preprint arXiv:2311.03412 (2023 ).
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Cold dark matter is almost all over according to the basic cosmological model, so it likely plays a function in the mergers of supermassive black holes. In this new research study, the group considers a variation on dark matter known as fuzzy dark matter. Given that these particles wouldnt interact with each other by anything other than gravity, they wouldnt clump in rather the very same method as regular dark matter, and hence have a more “fuzzy” circulation.
Fuzzy dark matter was first proposed to address what is known as the cusp problem of dwarf galaxies, which is a weak point for dark matter. Here the authors reveal that fuzzy dark matter can increase the rate of orbital decay for black holes, particularly the largest of supermassive black holes.

When galaxies collide, their supermassive black holes enter into a gravitational dance, gradually orbiting each other ever closer till ultimately … combining. Now a new paper recommends part of that mystery can be resolved with a bit of dark matter.