[CraigS]

Hi Rob;

Thank you for taking the time to draw and describe where you’re coming from. Much appreciated.

Fascinating.

As I highlighted in my conversation with Steven, I suppose we (meaning I), should evaluate this theory within the bounds it establishes for itself. Unfortunately, I have a feeling that the ‘lensing’ topic falls outside of those boundaries.

We know lensing exists, because we’ve observed it (ie: its now beyond a theoretical prediction). Its not mentioned in the paper. I suppose this is to be expected from a purely theoretical topic/paper. Curiously though, he specifically looks towards voids for finding anti-matter clumps, (of 'tens of Mpcs, no less !), which might support his theory. (This would be a practical, empirical step, which would then take it outside of theoretical boundaries).

How an anti-matter lens would form and remain stable, around some cluster/galaxy (object) etc, is difficult to envisage. Firstly, I believe that in all instances so far discovered, the foreground object is composed of normal matter. If anti-matter were to remain from the initial stages of formation, then what keeps it around the object ? What about where the normal matter comes within the proximity of the anti-matter ? Lagrange points would be everywhere, with both repulsive and attractive forces surrounding these points.

Ok, so lets imagine somehow, the forces cancel eachother and that’s what keeps the lens there. Ok, we somehow have a stable anti-matter grav lens in the midst of normal matter. I agree with Steven's approach of viewing the behaviour of this region, in the same way we'd view 'normal matter' field interactions. (What else do we have to go on ? )

(Incidentally, regardless of how the lens interacts with a photon, what we’d see from Earth, remains a function of the distribution of the anti-matter in the lens, the shape of the object and its distance from the lens. I think we’d still see the same patterns. Ie: rings, arcs, multiple images, etc. The intersecting photons could transit any region listed above, and result in any or all effects).

Ok. I understand the matters you raise on ‘focal point’. You hit the nail on the head in your words:

Originally Posted by Robh

This is of course an ideal situation. Many lenses are not symmetric and there will perhaps be several focal points (somewhat like astigmatism in classical optics).
And, although a different mode of operation, we can also use the term magnification with regard to gravitational lensing.

I agree with what you say (in an ideal thin lens situation). One of the main areas of interest about gravitational lenses, comes from the fact that they are far from ideal. The images we see from them, is very much a function of:

Originally Posted by CraigS

The shape of the distortion in the image we see, is a function of:
i) the mass distribution of the lens

There may be multiple ‘lenses’, quite possibly with none of them having any well defined ‘focal points’. (I use the term here, in its strictest definitional sense).

Interestingly, the author of the paper focuses more on the possibility that anti-matter may be a candidate for Dark Energy. He makes no mention of lenses, or of Dark Matter’s influences on galaxy rotation. In his conclusion, he gives a half-hearted comment:

These new cosmological scenarios could eliminate the uncomfortable presence of an unidentified dark energy, and maybe also of cosmological dark matter, which, according to the Lambda-CDM concordance model, would together represent more than the 95% of the Universe content.

It was us who brought up the lensing issue, and lensing effects are a much more complex than we might initially imagine.

Cheers & Rgds