Advantage Inhomogeneity

On 2/23/2016 8:51 AM, Phillip Helbig (undress to reply) wrote:
In article , "Robert L.
Oldershaw" writes:

You mean to say *statistical* homogeneity,

That should go without saying.

and to make such a claim
you must be ignoring the inconvenient and highly fractal cosmic web
via coarse-graining.

The term "coarse-graining" has a very specific meaning in physics. Why
not say "averaging"?

The consensus is that the cosmic web is not highly fractal by any useful
definition of the term. In particular, there is a scale above which no
further structure seems to exist.

Although I believe your statement, your argument would not
contradict fractal properties at all!

May I refer you (again) to the coast of Britain[*]?
http://www.vanderbilt.edu/AnS/psychology/cogsci/chaos/workshop/Fig4.2.GIF

The figure shows its fractal dimension over 2 orders of
magnitude, which suffices to call it fractal. Even though
though there is a scale above which no further structure
exists. (That scale is simply the size of Britain. You
can call it Great Britain instead, but it still is fixed!)

One can also nicely see here that Britain's coast does have
a relatively large fractal dimension: 1.24, instead of, for
instance, only 1.04 for South Africa. And Australia is also
clearly lagging behind.
[*] NB: there may be better data, this one just showed up.

--
Jos

On 2/23/16 1:40 AM, Phillip Helbig (undress to reply) wrote:
In article , "Richard D. Saam"
writes:

Is there a "simple" logic to explain the consistent sizes of:

1. Stellar planetary systems
2. Galaxies

throughout the visible universe?

Depends on the definition of "simple". Galaxies range over several
orders of magnitude, so "consistent size" is a non-starter here. Larger
galaxies haven't had time to form, smaller ones have been eaten by
larger ones. More or less. I don't think this is an outstanding
puzzle.

As for planetary sytems, we have much less data. As far as our own
Solar System goes, if the Oort cloud were much farther away, it probably
wouldn't be stable due to perturbations from other stars. So, again, I
don't see any mystery here.


I replace 'consistent' with 'near equilibrium' or 'asymptotically
approached' to which indicates our milky way as the standard
to which galaxies in various forms of creation
are to be compared.
In this context our solar system is at 1.5x10^15 cm
and the milky way at 5.5x10^22 cm
This is ~7 orders of magnitude
which would appear to required some type of modeling to explain.

On Tuesday, February 23, 2016 at 2:51:27 AM UTC-5, Phillip Helbig (undress to reply) wrote:

Just this morning on the arXiv:

Title: Reconciling dwarf galaxies with LCDM cosmology: Simulating a
realistic population of satellites around a Milky Way-mass galaxy
Authors: Andrew R. Wetzel, Philip F. Hopkins, Ji-hoon Kim, Claude-Andre
Faucher-Giguere, Dusan Keres, Eliot Quataert
Categories: astro-ph.GA
Comments: 6 pages, 5 figures. Submitted to ApJ Letters

You often mention arXiv papers here. In fairness, shouldn't you have
mentioned this one? It explicitly addresses things you are interested
in.


Well, if it came out "Just this morning..." it may be a bit early for
me to be rushing to judgement.

Do you really think this will be the end of the debate on the many
well-known LCDM problems associated with dwarf galaxies, their dark
matter contents, distribution, etc?

The Latte Project is a SIMULATION that gives desired answers, if one
wants to prop up the LCDM model and increae one's chances of getting
further grants, not to mention getting the blessings of like-minded
colleagues.

Maybe we should take a breath and see how other astrophysicists
evaluate the quality of the simulation and its assumptions, not to
mention the statistical uncertainties in their results.

Finally, please note that I tend to reference actual real world
observations of cosmological phenomena, rather than put my money on
simulations. And you are wrong about the cosmic web - big filaments
and little filaments and little filaments have lesser filaments. It
has more structure than you give it credit for.

Robert L. Oldershaw
http://www3.amherst.edu/~rloldershaw
Discrete Scale Relativity

In article , "Richard D. Saam"
writes:

Is there a "simple" logic to explain the consistent sizes of:

1. Stellar planetary systems
2. Galaxies

throughout the visible universe?

Depends on the definition of "simple". Galaxies range over several
orders of magnitude, so "consistent size" is a non-starter here. Larger
galaxies haven't had time to form, smaller ones have been eaten by
larger ones. More or less. I don't think this is an outstanding
puzzle.

As for planetary sytems, we have much less data. As far as our own
Solar System goes, if the Oort cloud were much farther away, it probably
wouldn't be stable due to perturbations from other stars. So, again, I
don't see any mystery here.

I replace 'consistent' with 'near equilibrium' or 'asymptotically
approached' to which indicates our milky way as the standard
to which galaxies in various forms of creation
are to be compared.

OK, but you are comparing galaxies which range over 6 or 7 orders of
magnitude in mass.

In this context our solar system is at 1.5x10^15 cm
and the milky way at 5.5x10^22 cm
This is ~7 orders of magnitude
which would appear to required some type of modeling to explain.

OK, I see what you mean. To get galaxy masses, you need the size of
primordial fluctuations. The scale of stars is, I think, pretty well
understood. (The initial mass function is not, but the answer to the
question why 0.1--50 solar masses and not 4000 or whatever is.)

In article , "Robert L.
Oldershaw" writes:

You often mention arXiv papers here. In fairness, shouldn't you have
mentioned this one? It explicitly addresses things you are interested
in.

Well, if it came out "Just this morning..." it may be a bit early for
me to be rushing to judgement.

True, but in the case of other papers, you mentioned them pretty
quickly.

Do you really think this will be the end of the debate on the many
well-known LCDM problems associated with dwarf galaxies, their dark
matter contents, distribution, etc?

I don't know, but I don't see why not.

The Latte Project is a SIMULATION that gives desired answers,

All of the problems, you mentioned, every last one of them, are based on
the comparison of SIMULATIONS to observations. Either you accept
simulations as a tool in both cases or in neither.

if one
wants to prop up the LCDM model and increae one's chances of getting
further grants, not to mention getting the blessings of like-minded
colleagues.

The authors could probably sue you in court for libel. With no evidence
at all, you are accusing them of fraud.

Maybe we should take a breath and see how other astrophysicists
evaluate the quality of the simulation and its assumptions, not to
mention the statistical uncertainties in their results.

This is what the community does, day in and day out. As I mentioned,
this is not the first such work to arrive at such a conclusion, i.e.
that taking baryons into account solves some or all of the problems of
the CDM-only simulations.

Finally, please note that I tend to reference actual real world
observations of cosmological phenomena, rather than put my money on
simulations.

Then why do you claim that LCDM has problems? As I mentioned, any such
problems are due to comparison between observations and simulations.

On Tuesday, February 23, 2016 at 2:41:11 AM UTC-5, Phillip Helbig (undress to reply) wrote:
In article , "Richard D. Saam"
writes:

Is there a "simple" logic to explain the consistent sizes of:

1. Stellar planetary systems
2. Galaxies

throughout the visible universe?

Depends on the definition of "simple". Galaxies range over several
orders of magnitude, so "consistent size" is a non-starter here. Larger
galaxies haven't had time to form, smaller ones have been eaten by
larger ones. More or less. I don't think this is an outstanding
puzzle.

As for planetary sytems, we have much less data. As far as our own
Solar System goes, if the Oort cloud were much farther away, it probably
wouldn't be stable due to perturbations from other stars. So, again, I
don't see any mystery here.
----------------------------------------------

I wonder if some specific references and actual observational information might clarify what are presented here as unsubstantiated conjectures.

To wit: http://arxiv.org/abs/1505.03534 , which has the title "The
Spitzer Survey of Stellar Structure in Galaxies (S4G): Stellar Masses,
Sizes and Radial Profiles for 2352 Nearby Galaxies"

This paper shows that the majority of galaxies have masses in the
relatively narrow mass range of about 10^8 to 10^11 solar mass, as
well as relatively narrow radius ranges, and there are well-defined
subpopulations with even narrower ranges. This was also well-known
back in the 1980s (See de Vaucouleurs paper in Science cited below).

[Mod. note: ask yourself whether this paper really tells us about the
'majority of galaxies' or simply the 'majority of galaxies in the S4G
sample'. Then google 'Galaxy mass function' -- mjh]

Also see for edification: http://arxiv.org/abs/1401.5799 by J.M. Shull
with the title "Where Do Galaxies End?". Here we do see cut-offs.

Regarding stellar scale systems, if you consider stars scientifically,
you will find what de Vaucouleurs published in his famous paper "The
Case For Hierarchical Cosmology", Science 1980, and that is that
stellar systems have relatively narrow mass and radius ranges, which
are even more narrow if they are classified into proper
subpopulations.

Exoplanets systems have a narrow mass range that parallels their
dominant stellar mass contribution. Their radius range is relatively
large, but then again so is the radius range for Rydberg atoms, which
as *any physicist* knows have radii that range from roughly 10^-7 cm
to 10^-3 cm (i.e., almost as big as some microbes).

Hope this citing of actual published scientific information helps.

[Mod. note: reformatted -- mjh]

Robert L. Oldershaw
http://www3.amherst.edu/~rloldershaw
Discrete Scale Relativity

On Thursday, February 25, 2016 at 7:43:38 AM UTC-5, Phillip Helbig (undress to reply) wrote:

The authors could probably sue you in court for libel. With no evidence
at all, you are accusing them of fraud.

------------------------------------------------------------

Sigh, I disagree with each point you make in the full comment, but as
you your self opined: 'there is no point of continuing' with
irrevocable differences of opinion.

However, I want to emphasize one particular error (aside from the lack
of specifically referenced scientific support) in your post. I am not
"accusing them of fraud", at least not in the legal sense of the term.
I am strongly suggesting that they are subject to the normal human
failings that are blatantly on display throughout the history -
specifically in science, and more generally in politics.


RLO
http://www3.amherst.edu/~rloldershaw
Discrete Scale Relativity

On 2/27/2016 10:00 AM, Robert L. Oldershaw wrote:
On Thursday, February 25, 2016 at 7:43:38 AM UTC-5, Phillip Helbig (undress to reply) wrote:

The authors could probably sue you in court for libel. With no evidence
at all, you are accusing them of fraud.


Sigh, I disagree with each point you make in the full comment,

it seems that "fraud" is really what were accusing them of, writing:
:The Latte Project is a SIMULATION that gives desired answers, if one
:wants to prop up the LCDM model and increae one's chances of getting
:further grants,

I read in that sentence that the simulation can be made to
give "desired results" if one "wants" them and that tha authors
also had a motif (getting further grants) to actually make use
of this possibility. Admittedly you don't yet write that they
actually did it, but explaining the possibility and giving
the motifs (you mentioned even more than one) is enough to
call it an accusation.

..
However, I want to emphasize one particular error (aside from the lack
of specifically referenced scientific support) in your post. I am not
"accusing them of fraud", at least not in the legal sense of the term.

Why not?

I am strongly suggesting that they are subject to the normal human
failings that are blatantly on display throughout the history -

So you now are really claiming that they *did it*. At least now
you are clearly accusing them of fraud! Because this behavior is
called fraud in science. It is not called "normal human failing".

specifically in science, and more generally in politics.

In science this is called fraud. We can leave out politics.

--
Jos