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trinitree88
2013-Nov-17, 05:26 PM
The authors devise a new scheme to reduce the tension in the data between Planck and type 1a supes. SEE:http://arxiv.org/abs/1311.3467

TooMany
2013-Nov-18, 03:55 PM
The authors devise a new scheme to reduce the tension in the data between Planck and type 1a supes. SEE:http://arxiv.org/abs/1311.3467

Can you trust adjustments that are specifically aimed at fixing disagreements? Perhaps reasonable arguments that increase the tension can also be found.

Hornblower
2013-Nov-18, 08:40 PM
Can you trust adjustments that are specifically aimed at fixing disagreements?Yes, if they are scientifically sound.
Perhaps reasonable arguments that increase the tension can also be found.

In which case I would say the theory needs more work.

TooMany
2013-Nov-19, 06:44 PM
What concerns me is a possible loss of objectivity. E.g., if a measurement agrees with theory there is little interest in attacking it's accuracy, but when it conflicts with theory there is great interest.

There was an article recently in Science News? raising doubt about many of the conclusions derived from experiments with human behavior. One problem discussed was that researchers tend to see what they expect to see.

While astronomy appears to be a more objective study than psychology, researchers in both fields may exhibit the same human tendencies. There is a high degree of certainty among cosmologist that current theory is correct.

Shaula
2013-Nov-19, 06:53 PM
There is a high degree of certainty among cosmologist that current theory is correct.
No there is not. Otherwise why would all these observations be being made? To test, to see if there is evidence for other models or new science. What there is a high degree of certainty is that no other models have so far proven as powerful predictively. As has been pointed out to you several times people do work on new ideas, do test alternative theories and they do want to 'break' the mainstream, almost every scientist I know has dreamed at some point of being the one to find a whole new paradigm.

Selfsim
2013-Nov-19, 09:03 PM
This study is about adjusting fitting curves to reflect new empirical data. The result also happens to remove some discrepancies between disparate interpretations of two different datasets (Planck and SN1a observations). The fact that the discrepency diminishes, improves the confidence level in the underlying model if the result had diverged, then the opposite would happen.

The refitting was done purely to assist in exploring the implications of a spatially flat cosmology.

I don't see any 'forcing' to make the models work here.

TooMany
2013-Nov-19, 11:42 PM
No there is not.

Let me put it this way. Observations are expected (rather than considered certain) to match the existing model. When they don't match, deeper consideration is given to what has actually been measured and what may be adversely affecting results. When they do match, quite naturally not much effort will be made to look for something that may be biasing the results.


Otherwise why would all these observations be being made? To test, to see if there is evidence for other models or new science. What there is a high degree of certainty is that no other models have so far proven as powerful predictively.

The actual predictive power is debatable. For example the ratios of elements is not quite predicted; the model is matched to the ratios measured by setting one or more model parameters to achieve a best fit.


As has been pointed out to you several times people do work on new ideas, do test alternative theories and they do want to 'break' the mainstream, almost every scientist I know has dreamed at some point of being the one to find a whole new paradigm.

Dreaming of other ideas is a good thing even if they don't quite fit. The early BB model was in fact found not to fit observation and inflation was proposed to retain a fit. Perhaps it's not such a good idea to rule out alternate models entirely because some aspect does not fit. If that requirement were applied to the BB model at the outset, it would have been discarded.

Shaula
2013-Nov-20, 07:20 AM
Let me put it this way. Observations are expected (rather than considered certain) to match the existing model. When they don't match, deeper consideration is given to what has actually been measured and what may be adversely affecting results. When they do match, quite naturally not much effort will be made to look for something that may be biasing the results.
Again, not true. Peer review. And most scientists will challenge papers they dislike the methodology of. I would concede that less effort goes into rigorously checking things that we were expecting to see but it is not 'not much' And often scientists go back to look at their old papers and find issues, or present it at a conference where someone will pipe up with "But..."


The actual predictive power is debatable. For example the ratios of elements is not quite predicted; the model is matched to the ratios measured by setting one or more model parameters to achieve a best fit.
Yes but the important thing is that by doing this for one part of the model other parts work better too. It has broad brush predictive power that we fine tune with observations. Like most models (would you throw out the Standard Model because we keep refining the masses of things?)


Dreaming of other ideas is a good thing even if they don't quite fit. The early BB model was in fact found not to fit observation and inflation was proposed to retain a fit. Perhaps it's not such a good idea to rule out alternate models entirely because some aspect does not fit. If that requirement were applied to the BB model at the outset, it would have been discarded.
The early BB model was found not to fit some observations so it was tweaked. You keep doing your best to present only the negative here. It worked for some things, not for others. It was an incomplete model that has been built on. It would not have been discarded because it fit a lot of observations and was fixable to fit the rest.

Jerry
2013-Nov-20, 05:58 PM
This study is about adjusting fitting curves to reflect new empirical data. The result also happens to remove some discrepancies between disparate interpretations of two different datasets (Planck and SN1a observations). The fact that the discrepency diminishes, improves the confidence level in the underlying model … if the result had diverged, then the opposite would happen.

The refitting was done purely to assist in exploring the implications of a spatially flat cosmology.

I don't see any 'forcing' to make the models work here.
The problem is that there is already a correction in the the supernova data reduction for Riemannian geometry. It is buried in the modified k-curves, used to factor in the relativistic components required in the supernova data reduction. See Hogg http://arxiv.org/pdf/astro-ph/0210394.pdf

It took a 'stretch' to the lean-out the supernova results to where a dark energy component worked at all - including only modest corrections, if any, for dust. There is also a general trend toward lower luminosity with increasing redshift when the 'stretch' factor is applied. Remember, Goldhaber and Perlmutter insisted they had looked at every possible error, and they could not escape the conclusion that a cosmological constant is necessary.

That said, there are a lot of parametric assumptions in both the supernova and Planck data sets. The real problem, is that the Planck data do not overlay the WMAP data; and although the shift may look small on paper, the correct solution might not included rationalization.

Whenever a theory requires a new or adjustable parameter to keep it aligned with new data extreme cautions is necessary. New parameters should always have an underlying physical assumption which conforms with known physical law. A good example are the thermal corrections to the Pioneer data. The corrections may-or-may not be correct, but at least they are based upon known physics. A better approach would be to build and launch two more probes that are specifically designed to look for unanticipated accelerations - space is so full of quirky 'gravity', we should used our ability to probe deep space and nail it down.

An example of a bad parametric adjustment is inflation: There are no physical roots to the inflationary theory; and since observations have demonstrated inflation does not remedy the structural problems inflation was conjured up to remedy in the first place; it should be discarded. Right now!

Selfsim
2013-Nov-21, 06:18 AM
The problem is that there is already a correction in the the supernova data reduction for Riemannian geometry. It is buried in the modified k-curves, used to factor in the relativistic components required in the supernova data reduction. See Hogg http://arxiv.org/pdf/astro-ph/0210394.pdfThanks ... I'll have a mull over that.


It took a 'stretch' to the lean-out the supernova results to where a dark energy component worked at all - including only modest corrections, if any, for dust. There is also a general trend toward lower luminosity with increasing redshift when the 'stretch' factor is applied. Remember, Goldhaber and Perlmutter insisted they had looked at every possible error, and they could not escape the conclusion that a cosmological constant is necessary.

That said, there are a lot of parametric assumptions in both the supernova and Planck data sets. The real problem, is that the Planck data do not overlay the WMAP data; and although the shift may look small on paper, the correct solution might not included rationalization.

Whenever a theory requires a new or adjustable parameter to keep it aligned with new data extreme cautions is necessary. New parameters should always have an underlying physical assumption which conforms with known physical law. A good example are the thermal corrections to the Pioneer data. The corrections may-or-may not be correct, but at least they are based upon known physics. A better approach would be to build and launch two more probes that are specifically designed to look for unanticipated accelerations - space is so full of quirky 'gravity', we should used our ability to probe deep space and nail it down. About Pioneer: well yeah, no problems with that idea (apart from the practicality/prioritisation aspects).


An example of a bad parametric adjustment is inflation: There are no physical roots to the inflationary theory; and since observations have demonstrated inflation does not remedy the structural problems inflation was conjured up to remedy in the first place; it should be discarded. Right now!Why is it so important to discard it? Inflation is a hypothetical added component, which is supported by, and is testable in, physical theory .. what is the downside of its inclusion? False vacuums exist in supercooled things, and scalar fields can slide down a potential energy slope .. aren't these its 'physical roots'?

Jerry
2013-Nov-24, 05:23 PM
Why is it so important to discard it? Inflation is a hypothetical added component, which is supported by, and is testable in, physical theory .. what is the downside of its inclusion? False vacuums exist in supercooled things, and scalar fields can slide down a potential energy slope .. aren't these its 'physical roots'?
The objection is philosophical; philosophy being the root of all scientific theory. Guth had two motivations for developing an inflationary epic: 1) The universe is too large to have a common origin in the time frame constrained by background temperatures. 2) There is too much structure (in the form of large galactic clusters) to have evolved in ~13 billion years.

Guth reasoned that their may have been a period of extremely rapid expansion in which structure also evolved, and that with sensitive enough instruments; we could find within the background the signatures - the waves in space and time necessary to develop structure. Each successive probe of the background: COBE, WMAP, and now Planck, have demonstrated a lack of the signature strength that would validate inflation as a testable, physically plausible theory. The flat rendition inflation has been relegated to doesn't link the background to a common root event; so the uniform temperature of the microwave background becomes an amazing coincidence, rather than the signature proof of an expanding, aging universe. Since neither of the motivations of inflation are satisfied by the observational data, it should be rejected as a scientific theory: It becomes an unknown.

Prior to Planck, the boundary conditions and constraints were barely touching. WMAP scientist pointed out that the overlap in the various constraints were so small, they could pin the age of the universe down to an incredibly precise number. But the Planck data requires a greater number, well out of the WMAP constraint; and inconsistent with the Dark Energy content constraint provided by the Supernova distance ladder. At this moment, we don't have a working model. Keeping inflation on-the-table implies we know and understand more that we do. It is melded into the Big Bang, where the physics are not known.

Selfsim
2013-Nov-24, 08:56 PM
Hmm .. I have no issues about distinguishing the 'unknown' parts in any theory or hypothesis. As an example, in a forum populated by numerous aspiring sci-fi writers however, unfortunately the 'unknown' is seen as fair ground for filling it in with tall stories. The 'place-holder' value in scientific theory is also akin to the placebo effect, which does actually result in measurable benefits. Such an effect should never outweigh the benefits of discovering something new about the nature of physical reality however, (IMO).

For what its worth, I'm personally not yet as convinced as you might be about inflation's non-fit in theory (not that this matters much). It could still account for what we see .. Relating to it as a philosophical 'unknown', is all good as far as I'm concerned.

But what to do with mainstream 'consensus-only' science components here at CQ?
Now that is the real question … :)

Cheers

Jerry
2013-Nov-29, 04:09 PM
Hmm .. I have no issues about distinguishing the 'unknown' parts in any theory or hypothesis. As an example, in a forum populated by numerous aspiring sci-fi writers however, unfortunately the 'unknown' is seen as fair ground for filling it in with tall stories. The 'place-holder' value in scientific theory is also akin to the placebo effect, which does actually result in measurable benefits. Such an effect should never outweigh the benefits of discovering something new about the nature of physical reality however, (IMO). A great scientist once told me that once you know, you are certain there is something wrong but you are not certain which part of the theory is wrong, this is when you go back and dig through all the 'tall stories', because somebody, somewhere likely had it right, or more nearly right. The situation is interesting, and it emphasis the fact that getting it 'right' can be as much a matter of good luck as good science. We don't have absolute guidance on the curves nature throws at us, and wrong turns can occur in any and every direction.


For what its worth, I'm personally not yet as convinced as you might be about inflation's non-fit in theory (not that this matters much). It could still account for what we see .. Relating to it as a philosophical 'unknown', is all good as far as I'm concerned. What irks me, is that inflation was a patch on a badly wounded theory, one that could not survive without it. But now inflation is no longer covering that initial wound, so in my mind, it remains an ugly scab and we still don't know what caused the wound in the first place, or how to heal it.


But what to do with mainstream 'consensus-only' science components here at CQ?
Now that is the real question … :)
I don't think anyone considers themselves 'consensus' scientists. everyone would like to break the mold. As a general rule, scientists from the different disciplines rely upon those with expertise within a discipline to ferret out new data and advance the field. Breakthrough science doesn't follow this rule, there is no guidance. Very often breakthroughs occur when someone outside the discipline steps in and points out the theory is mildewed.

Astrophysics could use a war right now; like the war waged between Sandage and Hoyle or Einstein and Bohr. I think it is time for the astrophysicists from India, Japan, and especially China to step up to the plate and say, 'The Americans and Europeans have held the reigns long enough'. I would like to see papers out of China that are divergent, rather than math-heavy beasts that parrot the mainstream flow. China, are you listening?

http://arxiv.org/pdf/1311.6872.pdf Toward inflation models compatible with the no-boundary proposal

trinitree88
2013-Dec-31, 03:27 PM
Here's a recent update to remove that tension....SEE:http://arxiv.org/abs/1311.3467
Still Wu, Yu, and Zhu...but Li is putting in his two cents worth. pete

Jerry
2014-Jan-02, 01:36 AM
This is an iffy, backdoor after-the-fact tweak of the knobs, and one that assumes there are no selection effects involved in determining cluster distance scaling; proofing once again that everything fundamental is sound.

Noted.

Jerry
2014-Mar-18, 12:08 AM
I think this is the first paper tracking the divergence between Planck and supernova cosmology:

http://arxiv.org/pdf/1310.3828v1.pdf COSMOLOGICAL CONSTRAINTS FROM MEASUREMENTS OF TYPE IA SUPERNOVAE DISCOVERED
DURING THE FIRST 1.5 YEARS OF THE PAN-STARRS1 SURVEY


The Pan-STARRS1 cosmological constraints are derived using the most recent external constraints from Planck, the Wiggle-Z BAO results, and the H0 constraint. Combining these external constraints with 112 high-redshift Pan-STARRS1 SNe Ia and 201 low-redshift SNe Ia, we find w =1 :186+0:076/-0:065, inconsistent with -1 at the sigma=2.4 level.

Shaula
2014-Mar-18, 06:54 AM
If we include WMAP9 CMB constraints instead of those from Planck , we fi nd w=-1:142+0:0760:087, which diminishes the discord to <2. We cannot conclude whether the tension with flat CDM is a feature of dark energy, new physics, or a combination of chance and systematic errors
Always good to quote the bits of an abstract that don't agree with your beliefs too. Makes you seem less prone to selection bias.

Reality Check
2014-Mar-18, 10:09 PM
We also have to consider that these are ~2 sigma differences and thus not considered definitive (e.g. a 5 sigma confidence is accepted as needed for discovery of a new particle).
The latest confirmation of inflation from BICEP2 is also at a ~2 sigma confidence.

John Mendenhall
2014-Mar-19, 01:32 AM
An informative and well mannered thread. Thank you all!