Undergrad Dark matter and old shell theorem

[trouble]

From an outsiders view, it appears that the old shell theorem is relevant to the dark matter issue: If one views a spherical cluster of galaxies as an interconnected structure, gravity would increase linearly with distance from the center and be greatest at the edge of the cluster.
For a spiral galaxy, that is more like a disk, there would be much less variation with distance ( a flat disk having none at all ) and orbital velocities should still be higher than expected when denying the applicability of the shell theorem.

I am wondering weather this proposition has been discussed anywhere and, if so, where? I would like to read up on it.

Thank you in advance.

 

[Bandersnatch]

I'm not sure what 'proposition' you have in mind, exactly. In any case, in order to find out how galactic gravitational potentials are modeled, you'll want a textbook or a course on galactic dynamics.

This might be of some use:
http://www.astro.utu.fi/~cflynn/galdyn/
(esp. module 3 & 4)

 

[trouble]

The proposition I have in mind is that "dark matter might be explained by applying the shell theorem". And, thank you for the link.

 

[Bandersnatch]

As you can see in the linked material, shell theorem is very much used in modelling galactic gravitational potentials - for those components that can be approximated as spherically symmetric matter distributions.
Once you add all the different components, you end up with a potential that is insufficient to explain the rotational velocities. Hence the need for dark matter.
When modelling galactic dark matter distribution as a spherically symmetric halo, you'd once again use the shell theorem.

It is a pretty basic piece of physics, after all.

 

[trouble]

Thanks again