Cold Spot in CMB: Real or Systemic Error?

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Discussion Overview

The discussion centers on the nature of the cold spot observed in the Cosmic Microwave Background (CMB) radiation, exploring whether it is a systemic error or a genuine cosmological anomaly. Participants examine various analyses and models related to this phenomenon, including implications for the Lambda Cold Dark Matter (LCDM) model and alternative cosmological theories.

Discussion Character

  • Debate/contested
  • Technical explanation
  • Exploratory

Main Points Raised

  • Some participants question whether the cold spot is a systemic error, citing its anomalous nature compared to surrounding areas.
  • Others reference the latest Planck analysis, which suggests the cold spot is anomalous and prompts searches for cosmological explanations.
  • A participant highlights that previous attempts to explain the cold spot through systematic artifacts or local astrophysical sources have not been successful, indicating it may represent a real feature of the CMB sky.
  • Concerns are raised about the implications of the cold spot and other CMB anomalies for the LCDM model, suggesting that these anomalies could challenge its validity.
  • One participant introduces a model called Coupled Gravity and Dark Energy (DEMC), proposing it as a potential explanation for the anomalies and other cosmological challenges, asserting that it aligns better with observed data than the LCDM model.

Areas of Agreement / Disagreement

Participants express differing views on the nature of the cold spot, with some suggesting it may be a real cosmological feature while others consider the possibility of it being a systemic error. The discussion remains unresolved regarding the implications for the LCDM model and the validity of the DEMC model as an alternative.

Contextual Notes

Participants note that the significance of the cold spot and other anomalies is complicated by the nature of Gaussian random fields, which can exhibit non-Gaussian features. The discussion also reflects uncertainty regarding the adequacy of current models to explain observed phenomena.

wolram
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Is this a systemic error?
Quote from wiki
The cold spot is mainly anomalous because it stands out compared to the relatively hot ring around it; it is not unusual if one only considers the size and coldness of the spot itself.[7] More technically, its detection and significance depends on using a compensated filter like a Mexican hat wavelet to find it.
end quote.
Or is it real?
 
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Hmm, thanks bapowell, from the paper:

. Attempts to explain the observed features in terms of systematic artefacts, local astrophysical sources of emission, or structure in the local Universe have not been successful. It is clear that these anomalies represent real features of the CMB sky.

IS the LCDM in danger?
 
Together with the other CMB anomalies, it certainly compels a raised eyebrow. The difficulty with assigning significance to these anomalies is that even Gaussian random fields will have features that appear non-Gaussian from time to time.
 
Thank you bapowell.
I have come across this paper: Cosmology with Coupled Gravity and Dark Energy

http://arxiv.org/pdf/1409.0782.pdf

It seems to me that it explains these anomalies and deals well with other problems::

Dark energy is a fundamental constituent of our universe, its status in the cosmological field equation should be equivalent to that of matter gravity. Here we construct a dark energy and matter gravity coupling (DEMC) model of cosmology in a way that dark energy and matter are introduced into the cosmological field equation in parallel with each other from the beginning. The DEMC universe possesses a composite symmetry from global Galileo invariance and local Lorentz invariance. The observed evolution of the universe expansion rate at redshift z > 1 is in tension with the standard LCDM model, but can be well predicted by the DEMC model from measurements of only nearby epochs. The so far most precise measured expansion rate at high z is quite a bit slower than the expectations from LCDM, but remarkably consistent with that from DEMC. It is hoped that the DEMC scenario can also help to solve other existing challenges to cosmology: large scale anomalies in CMB maps and large structures up to ∼ 103 Mpc of a quasar group. The DEMC universe is a well defined mechanical system. From measurements we can quantitatively evaluate its total rest energy, present absolute radius and expanding speed.
 

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