A message from bBeyond the red horizon? or just more epicycles?

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Discussion Overview

The discussion revolves around an anomaly in the Cosmic Microwave Background (CMB) radiation, specifically a power asymmetry observed in measurements from the Wilkinson Microwave Anisotropy Probe (WMAP). Participants explore potential explanations for this anomaly, including a proposed "superhorizon sinusoidal perturbation" to a curvaton field, and consider the implications for cosmological models and the interpretation of statistical data.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • Some participants reference a BBC article discussing the CMB anomaly and the proposed explanation involving a curvaton field.
  • Concerns are raised about the reliability of WMAP data due to its proximity to the resolution limit and the calibration process, suggesting that the findings may not be conclusive.
  • Sean Carroll's blog is mentioned as providing background on the statistical analysis of the CMB data, though some participants express skepticism about the boldness of his assertions.
  • One participant suggests that the universe could be finite and that our position within it might explain the observed anisotropies.
  • Another participant challenges the idea that a non-central position in a finite universe could account for the observed fluctuations, arguing against the presence of a gradient in fluctuation amplitude.
  • Speculation arises about the possibility of detecting pre-Big Bang phenomena by using lower frequency detectors.
  • There is a correction regarding the affiliation of the authors of the original report, clarifying that they are from Caltech, not Stanford.

Areas of Agreement / Disagreement

Participants express a range of views, with some supporting the proposed explanations for the CMB anomaly while others raise doubts about the data's reliability and the interpretations made. No consensus is reached on the implications of the findings or the validity of the proposed models.

Contextual Notes

Participants highlight limitations in the statistical analysis, including reliance on assumptions and the potential for imprecise calibration of data. The discussion reflects ongoing uncertainty and debate within the cosmological community regarding the interpretation of the CMB anomaly.

Who May Find This Useful

This discussion may be of interest to those studying cosmology, particularly in relation to the Cosmic Microwave Background, statistical analysis in astrophysics, and the implications of potential anomalies in observational data.

oldman
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The BBC are http://news.bbc.co.uk/2/low/science/nature/7440217.stm" by Erickcek, Kamionkowski, and Carroll of Stanford in which it is stated that:

"There is an anomaly in the CMB: measurements from the Wilkinson Microwave Anisotropy Probe (WMAP) ... indicate that the temperature-fluctuation amplitude is larger, by roughly 10% in one hemisphere than in the other. This power asymmetry occurs at the 99% C. L., and it cannot be attributed to any known astrophysical foreground or experimental artifact. This asymmetry has gone largely unnoticed".

They go on to explaining this anomaly (that had been previously swept under some carpet?) by postulating a "superhorizon sinusoidal perturbation to (a) curvaton field" postulated by "arXiv:hep-ph/0110096[/URL] among others, that contributes to inflation. It's the superhorizon part that seems to have generated the signature mentioned by the BBC.

Being in a curmudgeonly mood, I'm curious as to whether the cosmologial community have any comments on this development. Do they?
 
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The net fluctuation is too near the resolution limit of WMAP to be conclusive - especially considering the data was calibrated to filter out foreground noise. This is always an imprecise process that stretches the error bar. The Planck mission should further clarigy matters. Scientists are tempted to speculate in the face of unrefined data, which is entirely understandable. Being lucky is usually better than being good.
 
Sean Carroll give some background in his blog entry, http://cosmicvariance.com/2008/06/08/the-lopsided-universe/" .
 
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George Jones said:
Sean Carroll give some background ...[/URL].

Thanks, George, for this interesting link.

Comparing the claim by Erickec et al. that:

"This power asymmetry occurs at the 99% C. L., and it cannot be attributed to any known astrophysical foreground or experimental artifact"

with Chronos' appropriate remark that:

"The net fluctuation is too near the resolution limit of WMAP to be conclusive - especially considering the data was calibrated to filter out foreground noise. This is always an imprecise process that stretches the error bar. "

leads me to conclude that Mark Twain was right when he wrote:

"There are liars, damned liars and statisticians" !
 
Check the link George Jones posted to Sean Carroll's blog about this. It explains the statistics of this in a straightforward way.
 
Statistics rely upon assumptions. Sean Carroll makes too many bold assertions, IMO.
 
Chronos said:
Statistics rely upon assumptions. Sean Carroll makes too many bold assertions, IMO.

When you think of what astronomers have actually done, perhaps so. First, the CMB was a stretch to detect at all; radiation from a source at 2.7K is not the most obvious thing in the universe. Then, secondly, accurately establishing the BB nature of this faint source's spectrum (COBE) is standing ovation stuff. And thirdly, showing that the source subtends 4pi steradians uniformly, to one part in 10^4, is an extra tour de force. As for establishing the angular power spectrum of temperature fluctuations below this level; well, fourthly, the collective persistence that has prevailed among WMAP analysers must be unprecedented.

No wonder that the 10% perturbation discussed by Carroll, now a phenomenon at the 1 in 10^5 level from a faint source, is testing limits of analysis. But I still believe Mark Twain had the right take on statistical analysis.

Nevertheless, I suppose there is no reason why the universe, perhaps in a pre-inflationary state, should not have extended past what is now our observable universe. Maybe there really are sea-serpents out there!
 
I did not intend to be argumentative, especially with Wallace - a professional. I merely wished to point out the LCDM model has no serious rivals.
 
Maybe by lowering the frequency of the detector we can see what happened before the phase shift that we call the background radiation. I believe I read that someone is building a detector in the TV band. Has anyone any thoughts on that? Also if the big bang expanded at faster than light wouldn't at some point we reach a wall? I'm new to this physics help forum and I'm retired and no one I know wants to talk about cosmology. So please give me your thoughts.
 
  • #10
Hi,

Imagine a universe a bit like ours, but with a finite total mass and a definable centre. Say the enclosing volume of the total mass is larger than the visable volume but not infinite, at the given epoch and that the universe is expanding. Such a universe would look infinite and unbounded and any observer, even one near the "physical edge" would appear to be at the centre of such a universe, due to a conspiracy of effects due to gravitational and kinematic time dilation, abberation etc. However, depending on the density of the universe, there would be some small anisotropies for any observer not exactly at the centre because the "conspiracy of effects" is not perfect. Could that be what is being observed here? Could it be that we have actually managed to detect our non central position in a finite universe? Just a thought :)
 
  • #11
You would see this particular effect in the situation you describe. There is no large angle temperature anisotropy involved, rather the small small anisotropies are a greater amplitude (by a small amount) on one side than the other. I don't see how the situation you describe would give a gradient in fluctuation amplitude as you go out from the hypothetical centre of the Universe. I can see how this idea makes sense if there was a dipole temperature anisotropy, but not what is seen here.
 
  • #12
Key-- that is a deep thought but I've figured out that we are all at the center of the universe and would be no matter were we are located. If there is a reason for the 15% hotter hemosphere in the background radiation but it could be that the faster than light expansion didn't come to a symetrical stop due to fluctuations. This 4D bottle we are in is hard to visualize and I see the no center but if you are right it would really screw up my head to Visualize a universe were we are off center. I think we need more info.

milt
 
  • #13
oldman said:
This report traces back to a http://arxiv.org/PS_cache/arxiv/pdf/0806/0806.0377v1.pdf" by Erickcek, Kamionkowski, and Carroll of Stanford in which it is stated that:
Just a small correction as it is Caltech not Stanford.
 
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