Preferred axis in cosmology

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wolram
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Main Question or Discussion Point

Is there a preferred axis in cosmology, if there is what is the origin?

arXiv:1604.05484 [pdf, other]
Preferred axis in cosmology
Wen Zhao, Larissa Santos
Comments: 21 pages, 9 figures, 8 tables, invited review
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); General Relativity and Quantum Cosmology (gr-qc)

The foundation of modern cosmology relies on the so-called cosmological principle which states an homogeneous and isotropic distribution of matter in the universe on large scales. However, recent observations, such as the temperature anisotropy of the cosmic microwave background (CMB) radiation, the motion of galaxies in the universe, the polarization of quasars and the acceleration of the cosmic expansion, indicate preferred directions in the sky. If these directions have a cosmological origin, the cosmological principle would be violated, and modern cosmology should be reconsidered. In this paper, by considering the preferred axis in the CMB parity violation, we find that it coincides with the preferred axes in CMB quadrupole and CMB octopole, and they all align with the direction of the CMB kinematic dipole. In addition, the preferred directions in the velocity flows, quasar alignment, anisotropy of the cosmic acceleration, the handedness of spiral galaxies, and the angular distribution of the fine-structure constant are also claimed to be aligned with the CMB kinematic dipole. Since CMB dipole was confirmed to be caused by the motion of our local group of galaxies relative to the reference frame of the CMB, the coincidence of all these preferred directions hints that these anomalies have a common origin, which is not cosmological or due to a gravitational effect. The systematical or contaminative errors in observation or in data analysis, which can be directly related to the motion of our local group of galaxies, can play an important role in explaining the anomalies
 

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  • #2
DrSteve
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A preferred axis would violate the assumptions underlying GR of a homogeneous and isotropic (on a sufficiently large scale) universe. Yet GR does not necessarily describe the universe we actually live in.

However, the authors conclude that there likely isn't a preferred axis "Since CMB dipole was confirmed to be caused by the motion of our local group of galaxies relative to the reference frame of the CMB, the coincidence of all these preferred directions hints that these anomalies have a common origin, which is not cosmological or due to a gravitational effect. "
 
  • #3
phinds
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What do you suppose they could possibly mean by the "angular distribution of the fine-structure constant" ??? How does a dimensionless constant have an "angular distribution"?
 
  • #4
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What do you suppose they could possibly mean by the "angular distribution of the fine-structure constant" ??? How does a dimensionless constant have an "angular distribution"?
The fine structure constant can be estimated from cosmic observations no? So look at the estimated value as a function of position in the sky? At least that was my interpretation, but I'm just a layman...
 
  • #5
phinds
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The fine structure constant can be estimated from cosmic observations no? So look at the estimated value as a function of position in the sky? At least that was my interpretation, but I'm just a layman...
I think you need to look up the definition of the fine structure constant.

EDIT: hm ... I find that there may be more to the fine structure constant than I realized. I thought it was a simple ratio of factors in charged particle interactions and could not vary with position but that seems to be either debatable or wrong.
 
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I think you need to look up the definition of the fine structure constant.
Fair enough.

FWIW the reference given is http://arxiv.org/abs/1008.3907 which seems to talk about [itex]\Delta\alpha / \alpha[/itex] and how it varies.
 
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phinds
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Fair enough.

FWIW the reference given is http://arxiv.org/abs/1008.3907 which seems to talk about [itex]\Delta\alpha / \alpha[/itex] and how it varies.
My edit must have crossed this post in the ether :smile:
 
  • #8
PeterDonis
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I thought it was a simple ratio of factors in charged particle interactions and could not vary with position but that seems to be either debatable or wrong.
"Somewhat debatable" would best describe our current state of knowledge. Our best current theories predict that it is a constant, at least within our observable universe; but there are some observations which suggest it might vary. But it's only a suggestion, and AFAIK nobody has come up with a theoretical framework that predicts it should vary.
 
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phinds
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"Somewhat debatable" would best describe our current state of knowledge. Our best current theories predict that it is a constant, at least within our observable universe; but there are some observations which suggest it might vary. But it's only a suggestion, and AFAIK nobody has come up with a theoretical framework that predicts it should vary.
Thanks Peter.
 

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