# B What is the link between ordinary and dark matter?

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1. Dec 15, 2016

### Dee Flont

Unexpected interaction between dark matter and ordinary matter in mini-spiral galaxies

"We studied 36 galaxies, which was a sufficient number for statistical study. By doing this, we found a link between the structure of ordinary, or luminous matter like stars, dust and gas, with dark matter."​

“dark matter, according to the most hypotheses, would be non-baryonic or WIMP. It would not interact with ordinary matter except through gravitational force. Our observations, however, disagree with this notion."​

2. Dec 15, 2016

### Chalnoth

Personal note:
Hey, I was a postdoc at SISSA! I knew Paulo and interacted with him quite often when I was there. Definitely fun to hang out with.

As for this specific work, it comes with the usual caveats: the physics of normal matter with regard to galaxy formation is extremely difficult. I generally feel that it's going to always be very very difficult to rule out normal matter interactions for explaining anomalies in galaxy structure.

If I'm reading this paper correctly, they try to do this by showing that the galaxies don't appear to have any anomalous changes in structure as their mass changes, but nevertheless do not follow the NFW profile that is typically used for estimating dark matter halos.

Anyway, I feel this is generally interesting work, but this kind of research is really really hard, and we'd need a lot more evidence from many more directions to come to a firm conclusion that dark matter has significant non-gravitational interactions, or that there is something other than dark matter at work in these observations.

3. Dec 15, 2016

### Dee Flont

The following is more evidence of the same physical phenomenon as SISSA found which we are not allowed to discuss because it has to do with baryonic matter interacting with dark matter which is not what mainstream physics thinks occurs.

The Milky Way's dark matter halo appears to be lopsided

The emerging picture of the dark matter halo of the Milky Way is dominantly lopsided in nature.​

Offset between dark matter and ordinary matter: evidence from a sample of 38 lensing clusters of galaxies

Our data strongly support the idea that the gravitational potential in clusters is mainly due to a non-baryonic fluid, and any exotic field in gravitational theory must resemble that of CDM fields very closely.​

4. Dec 15, 2016

### stoomart

I believe the link is they both have gravity. The artlicle doesnt say what they're talking about other than saying:

5. Dec 15, 2016

### Chalnoth

First of all, SISSA didn't find it. SISSA is a school in Northern Italy.

Paulo Salucci and his student Ekaterina Karukes compiled some existing data to show that galaxy structure isn't what you'd naively expect from basic modeling assuming $\Lambda$CDM. The precise cause of this discrepancy isn't noted, just that there is a discrepancy and that discrepancy might be useful in understanding the nature of dark matter.

The problem with all of these is that they're all pretty vague in terms of what they mean for our universe. To move forward we need more than just vague discrepancies with the standard model. In particular, we need a concrete model that explains a number of discrepancies, across multiple independent observations. In other words, the model needs to explain some feature of the universe that is completely independent of galaxy structure for us to have confidence in the result.

6. Dec 15, 2016

### Staff: Mentor

Thread closed for moderation.

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