Is dark matter self-interacting with a velocity-dependent cross section?
In plain words
If dark matter particles collide with each other, the centers of halos are smoothed into cores, and some cores later collapse into very dense centers. The collision strength may depend on speed, being larger in small galaxies than in clusters.
Precise statement
Measure the self-interaction cross section per unit mass $\sigma/m$ ($\mathrm{cm}^2/\mathrm{g}$) as a function of relative velocity v from about $3 \times 10^{6}\ \mathrm{cm}/\mathrm{s}$ (dwarfs) to $10^{8}\ \mathrm{cm}/\mathrm{s}$ (clusters) using dwarf rotation curves, satellite central densities, strong-lens perturbers, cluster cores and cluster mergers. Kaplinghat, Tulin and Yu (2016, PRL 116, 041302) infer about $2\ \mathrm{cm}^2/\mathrm{g}$ at galaxy scales and $0.1\ \mathrm{cm}^2/\mathrm{g}$ at cluster scales. An answer is a nonzero $\sigma/m(v)$ detected at more than $3\sigma$, or an upper bound below $0.1\ \mathrm{cm}^2/\mathrm{g}$ at dwarf velocities.
What would settle it
A joint fit of dwarf, satellite, strong-lens and cluster data with self-interacting dark matter simulations that include gravothermal core collapse.
Status in the literature
Unverified note: it names recent work and was partly written without a live literature search; it awaits a check by an editor.
The dense $10^{6}\,M_{\mathrm{sun}}$ perturber found by gravitational imaging in JVAS B1938+666 (2025) has been interpreted as a core-collapsed self-interacting halo, an interpretation that is debated.
Parent problems
- Special case of What is dark matter made of? · open · from revision 1
Results
No results have been posted on this problem yet.
Post a result · how results are checked
Sign in to follow or save this problem
Comments (0)
Comments are not records: they are not signed, stamped or logged. How comments work
No comments yet.
Sign in to comment.