1) By reading second reference I cited above ? sorry by ?advertisements? again ? we see (Eq.4) that the ?kind of a theory featuring spin 2 field? is just GR + Eddington term. Well, (Eq.4) reduces to EH-action for gravity with renormalized G-constant (by dualities): (Eq.5 to 10), and comments therein.

Actually, he acknowledges the fact that actions are not completely equivalent – see the end of the page 4, this is exactly what I said above. He tries to go around saying that he is only interested in non-degenerate limit. A paragraph later he is talking about phase transition between g_{\mu\nu}=0 phase and normal EH phase – so he apparently does need degenerate limit. Sorry, I am not buying equivalence you are talking about.

es, sure, since it is just an integration constant (as \Lambda is!!).

No, is not an integration constant, it is cosmological constant (which he introduces in his model by hands by the way – since “dualities” do not work for case).

I see no great problem on that, since CDM models have to postulate a hole distribution of dark matter to fit galaxy curves that ?constant?.

Well, if you want to consider solutions without spherical symmetry (unfortunately, you have to – spiral galaxies are not really spherical) in Banados’ model, then guess what happens?

By the way, how do you explain the physics of bullet cluster in this model?

Cheers,
Dmitry.

Having said that however MOND does not mean that GR needs a modification. It could be due to backreaction as argued by David Wiltshire or it could be dark matter is made up of dipolar particles as argued by Luc Blanchet.

1) By reading second reference I cited above — sorry by “advertisements” again — we see (Eq.4) that the “kind of a theory featuring spin 2 field” is just GR + Eddington term. Well, (Eq.4) reduces to EH-action for gravity with renormalized G-constant (by dualities): (Eq.5 to 10), and comments therein.

2) “What defines the value of this integration constant? I am supposed to find a fit for any galaxy separately?”. Yes, sure, since it is just an integration constant (as \Lambda is!!). I see no great problem on that, since CDM models have to postulate a hole distribution of dark matter to fit galaxy curves that “constant”. On the other hand, “Ugly MOND” could not give you some sensible CDM for FRW-cosmology!
However, if one want to know how G-runs depending just on the observable matter distribution, I agree with you that a more “elaborated” theory is needed. This means, a coupling between EH and Eddington pieces of action is needed. That is not a great problem, since available options are constrained.
For instance, you can check new developments following (0807.5088) on arxiv that show so-called “EBI-GR” applied on cosmology (e.g. arXiv:0801.4103 or arXiv:0811.1272). But, this new “developments” are someway “less economical” (in Occam’s sense).
Cheers,

Rafael

Palatini formalism, tetrad formulation etc. etc. is only equivalent to Einstein-Hilbert GR if the metric is not degenerate. That’s however exactly the limit that Banados wants to discuss. In other words, I don’t quite see why you say this approach is conservative. He does use some kind of a theory featuring spin 2 field, but it’s not a GR in the sense we know it.

Second, I don’t quite see any fit for galaxy rotation curves in his papers. All he does is writing a spherically symmetric solution for his theory and showing that it has a constant asymptotics at r=0 which is determined by an integration constant. What defines the value of this integration constant? I am supposed to find a fit for any galaxy separately? If so, ugly MOND does a better job – you need just one parameter to fit all curves, for all spiral galaxies you see on the sky. In other words, I am yet to see why you call his approach “successful”.

But if you have an answer to these two questions, sure, let us discuss – the idea is so crazy that it seems interesting.

Cheers,
Dmitry.

Yes, we may disagree about my writting style . However, I prefer to see that as an “advertisement” (If you wish) to the idea of understanding CDM by using GR and “Occam?s Razor”, i.e. without exotics.
Ok, back to your comments.
Well, by reading the aforementioned article one sees that the author uses Einstein?s GR and considers some additional (g->0) limits. That limit was first observed by Eddington (e.g. see http://xxx.lanl.gov/abs/0807.5088 and Refs), but, which was not really exploited in astrophysics.
So, I consider it “conservative (yet successful)” since:
(1) The due profiles for circular motions of galaxies are obtained (without dark matter).
(2) Resulting FRW equations contain an additional matter sector as in CDM models, due to g->0.
(3) The used formalism is “just” Palatini action for gravity (with a cosmological constant) plus well-known duality transformations (see Refs.).
So, to best of my knowledge, it seems a very simple “CDM without CDM” approach to experimental puzzles… isn?t it?
Cheers,

Rafael.

if the author of the comment wasn’t Maximo, I apologize

Still, you write “more conservative (yet successful)” – which sounds again as a blatant advertisement to me In which respect, a theory featuring zeros of can be considered more conservative? And in which respect it is successful?

Cheers,
Dmitry.

it is not Maximo here. Neither somebody doing “advertisement” for him. But, naturally, I think you could have checked it, since IP locations didn?t match, right?
I am just sending a question (and related paper) because, after having read some posts in your blog, from people “explaining” CDM using “exotics”, I personally believe readers would be awared about more conservative (yet succesfull) approaches!
Cheers,

Rafael.

I am afraid, a blatant advertisement of your own paper (like the one above) is not really acceptable on NEQNET On the other hand, a smarter advertisement – in the form of the question “Dear Dmitry, is it possible to write a guest post about … on NEQNET?” – is acceptable. The answer is not guaranteed to be positive, though.

Cheers,
Dmitry.

are people discussing interesting alternatives to CDM, such as that
http://xxx.lanl.gov/abs/hep-th/0701169 in the conference?
Please, let us know!
Thanks.