Precise and Accurate, or Imprecise and Inaccurate

In article , Eric Flesch
writes:

Two new pre-prints with contrasting results are out, kind of like the
scientific equivalent of a food fight. It's a hot topic, the CMB

Actually, quite cold, methinks. :-)

temperature as a function of redshift -- which, if true, makes any
static model untenable.

It would certainly make a static model more difficult than it is
already.

On 24 December arxiv:1212.5456 (accepted by A&A): "A precise and
accurate determination of the cosmic microwave background temperature
at z=0.89" by S. Muller et al determines a CMB temp of 5.08K for PKS
1830-211 at z=0.89, although they stated some assumptions,
particularly page 2 column 2 top "of great importance for our study"
that the emission is behind the absorbing gas.

On 27 December arxiv 1212.5625 (accepted by ApJ): "On Measuring the
CMB Temperature at Redshift 0.89" by M. Sato et al, determines a CMB
temp of 1.1 - 2.5K for this same galaxy! They pointedly assert that
high-resolution imaging shows that the absorbing gas covers at best
only part of the emitter.

There have been determinations of the CMB temperature at high redshift
in the past.

Appreciate if anyone can shed better light on this.

Not light, but maybe some microwaves. :-)

The general expectation is that the CMB temperature INCREASES with
redshift. How many papers find this, and how many find something else?

Not really relevant here, but IIRC, 1830-211 is a gravitational-lens
system. Any static model needs to QUANTITATIVELY explain the huge
amount of gravitational-lens data.

On Sun, 30 Dec 12, Phillip Helbig wrote:
There have been determinations of the CMB temperature at high redshift
in the past. ...
The general expectation is that the CMB temperature INCREASES with
redshift. How many papers find this, and how many find something else?

Sure, Phil, but consider these points from this incident:
(1) Team A (1999) found disagreement but did not publish
(2) Team B (2012) found agreement and published.
(3) Team A published in 2012 to balance Team B's finding.

Now consider this, Phil: If it hadn't been for Team A's prior effort,
Team B's affirmative finding would have been published alone. All
would have hailed it as yet another confirmational finding, even
though the paper itself is littered with qualifiers (which you will
see if you read it). But Team A, using VLBI, showed that Team B's
finding is not reliable. (By the way, one member of Team B proof-read
Team A's paper, and another member of Team B was the referee.)

Therefore, how many other such findings have gone unchallenged simply
because there was no other "Team"? Note also from this incident that
papers are more likely to be published when they agree with the
current wisdom -- Team A did not publish for 12 years. So it is
entirely plausible that efforts on this front go 50-50, but the
affirmative ones publish and the negative ones do not.

Not really relevant here, but IIRC, 1830-211 is a gravitational-lens
system. Any static model needs to QUANTITATIVELY explain the huge
amount of gravitational-lens data.

So you mean, we need to explain the lensing angles in the absence of
the modelled "dark matter". Good point!

Eric

In article , Eric Flesch
writes:

The general expectation is that the CMB temperature INCREASES with
redshift. How many papers find this, and how many find something else?

Sure, Phil, but consider these points from this incident:
(1) Team A (1999) found disagreement but did not publish
(2) Team B (2012) found agreement and published.
(3) Team A published in 2012 to balance Team B's finding.

Of course, you are speculating on the motivation in (3).

Therefore, how many other such findings have gone unchallenged simply
because there was no other "Team"? Note also from this incident that
papers are more likely to be published when they agree with the
current wisdom -- Team A did not publish for 12 years.

Again, you are making an assumption without much justification then
extrapolating from it.

So it is
entirely plausible that efforts on this front go 50-50, but the
affirmative ones publish and the negative ones do not.

I agree that publication bias is a serious issue, but it cuts both ways.
A&A has (or at least had at one time; I don't know if it is still true)
a policy of not publishing "boring" results, i.e. those that agreed with
current wisdom and offered nothing new. In some cases, NATURE tends to
be less critical of surprising results and in some of those cases
wouldn't have published them had the result been more in line with
expectations.

Not really relevant here, but IIRC, 1830-211 is a gravitational-lens
system. Any static model needs to QUANTITATIVELY explain the huge
amount of gravitational-lens data.

So you mean, we need to explain the lensing angles in the absence of
the modelled "dark matter". Good point!

Not just that. The basic idea of gravitational lensing is quite old,
even older than relativistic cosmology, but the theory was put in place
only after relativistic cosmology was established. So, it was developed
with relativistic cosmology in mind, and seems to work quite well. The
analysis of a gravitational-lens survey is a huge undertaking, and the
fact that the cosmological parameters derived from it agree with those
from much simpler (at least conceptually) tests is a huge argument in
favour of the underlying assumptions being correct. Any alternative
model would have to explain why it works if the underlying model is
different. Another example, Arp and others have questioned the
cosmological nature of some high-redshift objects, particularly QSOs.
But there are many examples of lensed QSOs, and in all cases the
redshift of the QSO is higher than that of the lense. If the high
redshifts had another origin, we would expect at least a few examples of
a source with a lower redshift than the lens. (In some cases, Arp has
attempted to explain gravitational-lens systems by claiming that the
multiple images are multiple objects emitted from the lensing galaxy, in
line with his claim that such ejected objects have large
non-cosmological redshifts, but this seems like a HUGE epicycle to save
the appearances of his ideas.)

On Mon, 31 Dec 12, Phillip Helbig wrote:
analysis of a gravitational-lens survey is a huge undertaking, and the
fact that the cosmological parameters derived from it agree with those
from much simpler (at least conceptually) tests is a huge argument in
favour of the underlying assumptions being correct.

Agreed, although that "missing matter" is a required part of the
picture should put the spanner in, at least a little.

Another example, Arp and others have questioned the
cosmological nature of some high-redshift objects, particularly QSOs.

Ah yes, I once considered Arp's ideas. As a matter of fact, it helped
motivate my earliest cataloguing efforts back in the late 90's,
because I thought the additional data would show whether Arp's ideas
of QSO patterns around large (NGC-type) galaxies would hold. I
corresponded with Arp on the topic, and we collaborated on my first
paper (http://adsabs.harvard.edu/abs/1999astro.ph..7219F). But the
final outcome was that his model was not supported by the additional
data because the large data would be expected to randomly produce the
numbers of patterns that were found. And as attractive as the concept
of "intrinsic redshift" is, today I believe all quasars are at their
cosmological-redshift distance.

Eric

In article , Eric Flesch
writes:

On Mon, 31 Dec 12, Phillip Helbig wrote:
analysis of a gravitational-lens survey is a huge undertaking, and the
fact that the cosmological parameters derived from it agree with those
from much simpler (at least conceptually) tests is a huge argument in
favour of the underlying assumptions being correct.

Agreed, although that "missing matter" is a required part of the
picture should put the spanner in, at least a little.

Very little. Actually, this seems to me the simplest explanation, since
otherwise the assumption is that all matter is visible. Dark matter is
seen by some pundits as an epicycle put in to save the appearances.
However, there is no reason to expect all matter to be visible by
default. Indeed, there is baryonic matter which is not in stars, which
was also considered "missing matter". Then it was detected (e.g. via
X-ray emission of hot gas in clusters). OK, due to constraints from
primordial nucleosynthesis, we now know that most of the dark matter is
non-baryonic but, again, it seems rather anthropocentric to believe that
all matter must be baryonic. We live on a planet, but we don't expect
all matter to be in planets. The difference is that we knew that stars
existed before starting to think about missing mass. If non-baryonic
matter had been detected before modern cosmology came into being, no-one
would consider non-baryonic matter to be strange.

On 1/1/13 6:43 AM, Phillip Helbig---undress to reply wrote:
OK, due to constraints from
primordial nucleosynthesis, we now know that most of the dark matter is
non-baryonic
I would like to hear the logic underlying this statement.
Isn't our knowledge of primordial nucleosynthesis
based on nuclear species ratios ie H/He or H/Li
and not absolute mass of each species
and these ratios are termed abundances?
Observation of these abundances in the present era
substantiates a primordial nucleosynthetic origin.
But this does not negate the possibility
of primordial nucleosynthetic species ie H/He or H/Li
in a different physical density phase
that remains invisible in the present era.

It would be like the calcium and carbonate species in the ocean
at very small concentrations (milli-equivalents/liter)
but in equilibrium with large calcium carbonate 'chalk' geological
formation (tons and tons) such as the white cliffs of Dover
and having the same calcium/carbonate 'abundance' ratio
but invisible to an oceanic observer.

RDS

In article , "Richard D. Saam"
writes:

OK, due to constraints from
primordial nucleosynthesis, we now know that most of the dark matter is
non-baryonic
I would like to hear the logic underlying this statement.
Isn't our knowledge of primordial nucleosynthesis
based on nuclear species ratios ie H/He or H/Li
and not absolute mass of each species
and these ratios are termed abundances?
Observation of these abundances in the present era
substantiates a primordial nucleosynthetic origin.
But this does not negate the possibility
of primordial nucleosynthetic species ie H/He or H/Li
in a different physical density phase
that remains invisible in the present era.

One parameter is the photon-to-baryon ratio. We can count the photons,
so we know the total number of baryons. (Almost all photons are in the
CMB, by the way.)

On 1/2/13 2:59 AM, Phillip Helbig---undress to reply wrote:
In article , "Richard D. Saam"
writes:

OK, due to constraints from
primordial nucleosynthesis, we now know that most of the dark matter is
non-baryonic
I would like to hear the logic underlying this statement.

One parameter is the photon-to-baryon ratio. We can count the photons,
so we know the total number of baryons. (Almost all photons are in the
CMB, by the way.)

The photon density rho_p = 413/cm^3
reflects the Black Body calculation at 2.73 K
and actual photon counting (WMAP)
The critical density rho_c is separately calculated
at (3/8pi)*H^2/G = 9.56E-30 g/cc

It is understood that
rho_c*(1+z)^3/rho_p*(1+z)^3
is constant
and expressed in terms of hydrogen atoms
rho_c*(1+z)^3/(Avogadro*rho_p*(1+z)^3)
is constant
and that .0464 (WMAP) of critical density is baryonic
as measured by Baryonic Acoustic Oscillation at z=1100.

It would appear that knowing the photon density rho_p
does not dictate the number of baryons.

RDS

In article , "Richard D. Saam"
writes:

OK, due to constraints from
primordial nucleosynthesis, we now know that most of the dark matter is
non-baryonic
I would like to hear the logic underlying this statement.

One parameter is the photon-to-baryon ratio. We can count the photons,
so we know the total number of baryons. (Almost all photons are in the
CMB, by the way.)

The photon density rho_p = 413/cm^3
reflects the Black Body calculation at 2.73 K
and actual photon counting (WMAP)
The critical density rho_c is separately calculated
at (3/8pi)*H^2/G = 9.56E-30 g/cc

It is understood that
rho_c*(1+z)^3/rho_p*(1+z)^3
is constant
and expressed in terms of hydrogen atoms
rho_c*(1+z)^3/(Avogadro*rho_p*(1+z)^3)
is constant

We can elimate (1+z)^3 from the above and just say that the ratio is
constant.

and that .0464 (WMAP) of critical density is baryonic
as measured by Baryonic Acoustic Oscillation at z=1100.

We know the critical density, we know the fraction of baryons and thus
we know the number of baryons.

It would appear that knowing the photon density rho_p
does not dictate the number of baryons.

What I meant was that the predictions of big-bang nucleosynthesis depend
on this ratio, thus knowing the ratio ties down the predictions so that
there is no leeway.

On 1/3/13 1:20 PM, Phillip Helbig---undress to reply wrote:

What I meant was that the predictions of big-bang nucleosynthesis depend
on this ratio, thus knowing the ratio ties down the predictions so that
there is no leeway.

Does big-bang nucleosynthetic baryonic production
based on the photon-to-baryon ratio
assume Fermi-Dirac statistics
and not any Bose-Einstein statistical contribution?

RDS