Google ate my post. It seems that it happens when the message is
too big. Note to myself use an editor ;-).


On Mar 20, 1:34 pm, "Eric Gisse" wrote:
wrote:
Denying the weak lensing results is even more closed minded than me
disagreeing with what you thinkMONDmeans.

I never denied weak lensing results. I just said that if MOND can
explain the Mass Discrepency in Galaxies, it is not very difficult to
assume that a proper quantum theory will account for the Mass
Discrepency in weak lensing data also.

I also am not against Dark Matter. I just dislike Cold Dark Matter. In
my opinion Cold Dark Matter means that it is not moving much. And if
there are huge amounts of it, it will clump. If it clumps there will
be collisions. How does one detect these collisions, if they do not
couple electromagnetically.

Neutrinos avoid this problem by being hot, which prevents their
coupling together.

Till yesterday I used to think that MOND will fail in Clusters but now
I think that MOND should apply within any gravitationally bound
structure. So now I think MOND should survive the KATRIN test. And
Neutrino oscillation will be able to provide the missing mass. But it
may not be true, and there may be another neutrino like particle that
is also present.

The thing is that all the evidence for Dark Matter is just Mass
Discrepency. The only proper evidence we have found for Dark Matter
is in Bullet Cluster and the dark galaxies. Both of these can be
explained currently by massive and fast Neutrinos. If neutrinos have
mass then they can make stable structures of Cluster sizes, given
MONDian force.


Because it is so much more easy to live with the status quo.
You don't want to face the possibility that we don't know any
theory that can account for weak gravity regimes. This is
actually a great time for theoretical physicists to try and
find the correct theory, and quite a few are working towards
them, and I am not talking about crackpots. Search for papers
on TeVeS, Conformal Loop Quantum Gravity, AdS/CFT gravity.

Start paring the list down.

Of these, how many of them make testable predictions? No, I don't mean
"soon", I mean "right here link to paper".

All of them.

It is only DM that does not make testable prediction. Others can be
falsified. Mannheim's Conformal Gravity has already been falsified by
Bullet Cluster. But now I know what was wrong with it. He was using
dS/CFT instead of AdS/CFT. Now M.B.Paranjape and A.Edery are taking
that work forward, using AdS/CFT. But the work must now be done from
the beginning.

We also have LQG. I don't think that you believe that they are not
trying to make any testable predictions. It is the only viable Quantum
Gravity Theory. I don't consider String Theory at all. LQG till now
had been using GR. Which is not working very well. The main problem
is that Quantum theories are fundamentally at odds with any sort of
scale. There are a couple of LQG researchers that are moving towards
using Conformal Invariance instead of Lorentz Invariance. I am sure
something good will come out of it.

TeVeS is making testable predictions. I personally don't like TeVeS,
but it is not a bad idea. We may come up with a law for weak lensing
through it. This work is also needed for convincing GR proponents that
DM in Galaxies is redundant.


Of these, how many match _already verified_ predictions by general
relativity?

Conformal gravity matches GR very well in strong gravity. Nearly well
with MOND in the galaxies. Used to explain Cluster dynamics, but now
with the discovery of unambiguous proof of DM in Clusters will fail
there. And hence will be falsified.

MOND/TeVeS works well in strong gravity, as they are basically same as
GR. Works very well in Galaxies. Predicts HDM in Clusters, as required
by Bullet Cluster. Also is not against Dark Galaxies. It can be
falsified, but has not been falsified yet.

LQG is still in its infancy. Will have to wait for some testable
predictions. They have some explanation for the Ohmygod particles, but
I think little else.


Of the remaining, if any, match up with the area O' interest that is
the bullet cluster while removing the need for dark matter?

There is no need to remove Dark Matter in Bullet Cluster. It is an
unambiguous observation that Dark Matter exists in Bullet Cluster.
Also MOND has been predicting double the mass in most Clusters, which
should be the same Dark Matter which we see in Bullet Cluster. But
that doesn't mean that it has to be CDM, it could be HDM.


But it is a difficult thing to do, you have to be great at
mathematics. These theories are much more difficult to work
with mathematically than GR.

Considering how hard it is to use GR without making a large series of
approximations, I can't help but wonder how many of these theories are
at the point where they can make useful predictions rather than
sweeping statements from toy models.

Just imagine how hard it will be using AdS/CFT for the calculations.
It is an Order Four theory, much more complex than the Order 2 GR. It
is possibly the biggest reason why we don't have a viable Quantum
Gravity theory yet.

Why don't you studyMONDresults. TheMONDpeople cannot be
pulling numbers out of thin air. You can test them out. You can
try to make a model of DM that will fitMOND. But you won't do
that, you will simply ignore all the evidence, because that's
the easy thing to do.

Of course they aren't.

Keep in mind thatMONDoffers no explanation as to _why_ gravity is
being screwy, just that it _is_ screwy and that it _is_ a model of the
screwyness. There is no reason offered as to why dark matter can't
simply be modeled byMOND. It isn't as ifMONDis based off of bedrock
principles - it is an ad-hoc notion that fits the bill in certain
places.

MOND need not offer any explanation to be useful. It's main job is to
show that gravity is being screwy. The work is cut out for the
theoretical physicists to explain why it is screwy. But most are just
hoping that DM can explain anything. While even after 25 years there
is no model of DM that can explain MOND relationship.

I'm curious as to what the experiment described here will say.

http://physicsweb.org/articles/news/11/3/12/1

I don't know what they are trying to do. I think the person doesn't
know MOND. MOND will apply only when the total accelaration due to
gravity drops below a0. I don't know how on earth he found such a
place on earth. On earth acceleration due to gravity cannot go much
below or above g. Even earth can never expect gravity much less than
a0, unless it gets between Jupiter and Sun in such a way that both the
accelarations cancel exactly. Even then Moon will not let it fall
below a0.

The only place MOND can be tested is the L4 and L5 areas. In these
areas gravity due to Sun and Earth+Moon cancels exactly, so there must
be a smaller area within it where the total gravity falls below a0.
This area is called a Mondian bubble. And it is the nearest place
where MOND can be verified. The hope is that the bubble will be big
enough to accomodate a test machine ;-).

Do _NOT_ try to pull that "I'm fighting the establishment!" bull****
with me. The papers you cite are published in reputable journals.
Considering how _often_MONDis referred to in popular and technical
scientific articles,MONDis decidedly mainstream. The folks in here
who also cry about persecution have wet dreams about being given the
kind of attention thatMONDgets in the literature.

Sorry, will not do it again. It was an interesting comment in the
letter.

MONDis not a law.MONDis a model - it was designed as such, and
remains as such. The fact that it has any sort of success means
something - I think it means that it is keying in on the dark matter
distribution in galaxies at some level.

MOND is a law, it is only a single equation, just like Keplers laws
where. Or Newton's laws were. Mondian models are created to fit the
galaxy rotation curves. But these are not MOND. They are built over
MOND.

Think about the weak lensing results - where is most of the dark
matter? Out in the halo. Ignoring weak lensing - where does the dark
matter need to be to smooth out the velocities? Out in the halo. What
is the domain of application forMOND? Out...in the halo, where
gravity is thought to be "weaker".

I would think if most of the matter is out in a halo, the lens will
not be properly convex. It will be convex overall but near the center
there will be a concave circular portion. This will result in the
center part concentrating more light than a normal convex lens, so you
should see a brighter spot at the center of such a lens. Does any weak
lensing show this artifact.

Let me be clear - I accepted before and accept even more now thatMOND
is pointing to something important. What we seem to disagree on is
_what_ that important thing is.

Well now I can rejoice ;-). We have reached the most important part of
the discussion. You accept MOND effect as real.

Now consider the following points
1) MOND is real. This means that Dark Matter has no degrees of freedom
within a galaxy. This must be true because MOND can predict the
rotation curve based on normal matter alone, so if DM gives rise to
MOND, it cannot have any degrees of freedom. It must go where normal
matter tells it to.

2) We cannot be living in a special epoch, when DM matches MOND
everywhere. It must have been true for a very long time in the past.
And will
continue to do so for a very long time in the future.

3) Dark Matter cannot have been put by an intelligent agent to test
our faith ;-). It must have arisen based on some mechanism and using
the mechanisms of GR must have moved in such a way to always bring out
the MOND phenomenology.

4) If you see the 3 points above you see that DM in galaxies is
superfluous. It must satisfy too many features to be true, and top of
that it has no degrees of freedom, which makes it a superflous
concept. This is where Occam's Razor steps in to say that DM is not
simpler than MOND, and so must not be the true picture of the world.


2) Disk-Halo conspiracy

http://arxiv.org/PS_cache/astro-ph/pdf/9610/9610188.pdf[PDF is
slightly glitchy...]

One of the conclusions I thought was most intriguing was that the dark
matter halo shape under that model was something that was reasonably
constant.

It [disk halo conspiracy] is touched on indirectly as well by the
previous paper. Given there is an alternative explanation that is
entirely plausible, I don't see why folks are adopting the CDM
WROOOOOOOOONG stance. So far, it looks like the worst case is that the
CDM model needs tweaking - which doesn't surprise me, I do not believe
it was even geared as a model for scales so small.

What is your entirely plausible alternative explanation. I am dying to
know ;-).

What folks seem to be missing is that success ofMONDand success of
dark matter are not mutually contradictory goals.MONDseems to lend
itself fairly easily to a dark matter explanation, despite how angry
that probably makes theMONDcrew.

On the contrary, MOND is expected to make a lot of Relativists very
angry when they find that no DM model can work ;-).


The constant inclusion of the virial mass [200x universe critical
density] and the size associated with it amuses me for some odd
reason...I don't find anything wrong or objectionable, it just amuses
me.

I don't know what you mean exactly by "suitable definitions of
working", butMONDworks very well without any exceptions on the
scale of galaxies. In 80% of galaxies it gives very good fits,
for the rest of the 20%, it is known that there are problems with
the data. And the important thing is that it cannot fit those 20%,
as would be expected for a theory with no free parameters, a0 is
no longer free. Another important thing is that DM models can fit
those 20% cases also to the same degree of accuracy as the other
80%, because of the large number of free parameters.

The number of free parameters isn't that big and you know it, if you
have actually been reading the papers you have been citing me.

Even 2 free parameters are too many when a competing theory can fit
the data without any free parameter. And most DM theories require 3 or
4 parameters. Remember that DM theories can fit the 20% cases where
the data is problematic. This indicates that the free parameters are
enough to fit any rotation curve even if they are not from a real
galaxy. This is what proves that there are too many parameters. Any
good model is one which is not able to work with bad data. DM models
are not good models.

The onus is on theoretical physicists to find the underlying reason.
IgnoringMONDdoes not help.

That much is now obvious.MONDis an excellent model for individual
galaxies, though I _suspect_ it fails for galaxies that are products
of or are in various stages of collision [eg, bullet cluster].

Keep in mind that nothing you have shown me or what I have found
conclusively, or even most likely, makes dark matter an incorrect
model. In fact, everything I have seen thus far either supports or
refines dark matter. Using theMONDfits along with the empirical data
gives some nice constraints on entirely plausible distributions of
dark mater where there were none before, which is quite useful.

I and possibly all of the MOND proponents are dying to know an
entirely plausible distribution of DM that can fit MOND.

Just remember that Occam's Razor is against you ;-).

regards,
-anandsr