Shell structure topological defects as substitute for dark matter

[Ranku]

Recently a paper was published 'The binding of cosmological structures by massless topological defects' which proposes how 'massless' shells can bind galaxies in lieu of dark matter. There are a few basic technical details I am looking to clarify:

1. It is mentioned in the paper that an attractive force is exerted on a test particle riding a zero-mass shell. So, is the basic difference between Newtonian gravitational force and gravitational force in a shell, that in which the former propagates through spacetime, while the latter is entirely localized in spacetime?

2. The gravitational force decreases as 1/r in a massless shell. In order to produce a flat rotation curve in galaxies, does that therefore require each larger concentric shell to have greater mass, so that the gravitational force of the shells can act with the same magnitude upon stars at all distances in galaxies?

3. The paper seeks to offer an alternative to dark matter. But could it be also possible that dark matter particles are themselves miniature versions of massless shells?

 

[Ibix]

Link appears to go to a file on your desktop, not the paper.

 

[Ranku]

Link appears to go to a file on your desktop, not the paper.

Oops: corrected.

 

[renormalize]

Recently a paper was published 'The binding of cosmological structures by massless topological defects' which proposes how 'massless' shells can bind galaxies in lieu of dark matter.

This paper appears quite "hand wavy" to me. The proposed spherical shells are massless only because they combine shells of ordinary matter with shells of negative mass density, i.e., shells of exotic matter. Given the novel properties of gravitational systems incorporating exotic matter (stable wormholes, Alcubierre warp drive, etc.), it's no surprise that one can arrange to get a galactic 1/r potential this way. But as far as I can see, the author offers no explanation for the source of this exotic matter.