 |
| [image: kamere.com] |
Astronomers bring constitute that galaxies bring regularities that are hard to accommodate inward theories of particle nighttime matter, for illustration the Tully-Fisher relation together with the Radial Acceleration Relation. These observed patterns inward the measurements don’t follow all that easily from the uncomplicated models of particle nighttime matter. Thrifty theorists bring to invoke additional effects that are assigned to diverse astrophysical processes, notably stellar feedback. While these processes arguably exist, it isn’t clear that they genuinely human activity inward galaxies inward amounts necessary to explicate the observations.
In the past times twenty years or so, astrophysicists bring improved estimator simulations for galaxy formation until everything fit amongst the data, sometimes adapting the models to novel observations. These estimator simulations forthwith comprise most a dozen or together with so parameters (there are diverse simulations together with non all of them listing the parameters, together with so it’s hard to tell exactly) together with the results grip good amongst observation.
But I let on it somewhat hard to swallow that regularities that seem to survive generic inward galaxies follow from the theory only later on much fiddling. Indeed, the rattling fact that it took astrophysicists together with so long to instruct galaxies correct tells me that the patters inward our observations are non generic to particle nighttime matter. It signals that the theories are missing something important.
One of the proposals for the missing slice has long been that gravity must survive modified. But I, every bit many theorists, bring non been peculiarly convinced past times this idea, the argue existence that it’s hard to alter anything most Einstein’s theory of full general relativity without running into conflict amongst the many high precision measurements that are inward fantabulous understanding amongst the theory. On the other hand, modified gravity industrial plant dramatically good for galaxies together with explains the observed regularities.
For a long fourth dimension I’ve been rather agnostic most the whole issue. Then, iii years ago, I read a newspaper inward which Berezhiani together with Khoury proposed that nighttime affair is a superfluid. The argue I fifty-fifty paid attending to this had goose egg to practise amongst nighttime matter; at the fourth dimension I was working on superfluid condensates that tin mimic gravitational effects together with I was looking for inspiration. But I bring since expire a big fan of superfluid nighttime affair – because it makes together with so much sense!
You see, the superfluid that Berezhiani together with Khoury proposed at isn’t only whatever superfluid. It has an interaction amongst normal affair together with this interaction creates a force. This forcefulness looks similar modified gravity. Indeed, I think, it is justified to telephone phone it modified gravity because the trace acting on galaxies it forthwith no longer that of full general relativity alone.
However, to instruct the materials to condense, you lot involve sufficient pressure, together with the clitoris per unit of measurement area comes from the gravitational attraction of the affair itself. Only if you lot bring affair sufficiently clumped together volition the fluid expire a superfluid together with generate the additional force. If the affair isn’t sufficiently clumped, or is only every bit good warm, it’ll non condense.
This uncomplicated persuasion industrial plant remarkably good to explicate why the observations that nosotros assign to nighttime affair seem to autumn into ii categories: Those that fit ameliorate to particle nighttime affair together with those that fit ameliorate to modified gravity. It’s because the nighttime affair is a fluid amongst ii phases. In galaxies it’s condensed. In galaxy clusters, most of it isn’t condensed because the average potential isn’t deep enough. And inward the early on universe it’s every bit good warm for condensation. On scales of the solar system, finally, it doesn’t brand feel to fifty-fifty speak of the superfluid’s force, it would survive similar talking most van der Waals forces within a proton. The theory only isn’t applicable there.
I was pretty excited most this until it occurred to me there’s a work amongst this idea. The work is that nosotros know at to the lowest degree since the 170817 gravitational moving ridge trial amongst an optical counterpart that gravitational waves locomote to expert precision at the same speed every bit light. This past times itself is slow to explicate amongst the superfluid idea: Light only doesn’t interact amongst the superfluid. There could survive diverse argue for this, but regardless of what the reason, it’s uncomplicated to accommodate this inward the model.
This has the final result notwithstanding that lite which travels through the superfluid share of galaxies volition non answer to the volume of what nosotros commonly refer to every bit nighttime matter. The superfluid does bring mass together with thence also has a gravitational pull. Light notices that together with volition curvature to a greater extent than or less it. But most of the nighttime affair that nosotros infer from the motility of normal affair is a “phantom matter” or an “impostor field”. It’s genuinely due to the additional forcefulness from the superfluid. And lite volition non answer to this.
As a result, the amount of nighttime affair inferred from lensing on galaxies should non tally the amount of nighttime affair inferred from the motility of stars. My student, Tobias Mistele, together with I hence sent out to bring a expect at strong gravitational lensing. We only completed our newspaper on this together with it’s forthwith available on the arXiv.
- Strong lensing amongst superfluid nighttime matter
Sabine Hossenfelder, Tobias Mistele
arXiv:1809.00840 [astro-ph.GA]
This finding hence exemplifies why criticisms on modified gravity that insist on at that topographic point only existence 1 means to fit a galaxy are ill-founded. If you lot modify gravity past times introducing additional fields – together with that’s how almost all modifications of gravity function – the additional fields volition bring additional degrees of liberty together with to a greater extent than oft than non require additional initial conditions. There volition hence commonly survive several solutions for galaxies. Indeed, some galaxies may past times some statistical fluke non bring attracted plenty of the fluid for it to condense to get with, though nosotros bring constitute no evidence of that.
We bring been able to fit all lenses inward our sample – 65 inward full – except for one. The 1 outlier is a near-miss. It could survive off for a diverseness of reasons, either because the criterion is imprecise, or because our model is overly simplistic. We assume, for example, that the distribution of the superfluid is spherically symmetric together with time-independent, which almost sure isn’t the case. Actually it’s remarkable it industrial plant at all.
Of course of report that doesn’t hateful that the model is off the hook; it could soundless come across conflict amongst information that nosotros haven’t checked together with so far. That observations based on the passage of lite should demo an apparent lack of nighttime affair mightiness bring other observable consequences, for illustration for gravitational redshift. Also, nosotros bring only looked at 1 exceptional sample of galaxies together with those bring no detailed information on the motility of stars. Galaxies for which at that topographic point is to a greater extent than information volition survive to a greater extent than of a challenge to fit.
In summary: So far together with so good. Suggestions for what information to expect at side past times side are highly welcome.
Further reading: My Aeon assay “The Superfluid Universe”, together with my recent SciAm article amongst Stacy McGaugh “Is nighttime affair real?”
Comments
Post a Comment