Is There a Preferred Axis in the Cosmic Radiation Anisotropy?

[wolram]

http://arxiv.org/abs/astro-ph/0502237
The axis of evil
Kate Land and Jo˜ao Magueijo
Theoretical Physics Group, Imperial College, Prince Consort Road, London SW7 2BZ, UK
(Dated: Feb 11, 2005)
We examine previous claims for a preferred axis at (b, l)  (60,-100) in the cosmic radiation anisotropy, by generalizing the concept of multipole planarity to any shape preference (a concept we define mathematically). Contrary to earlier claims, we find that the amount of power concentrated
in planar modes for l = 2, 3 is not inconsistent with isotropy and Gaussianity. The multipoles’ alignment, however, is indeed anomalous, and extends up to l = 5 rejecting statistical isotropy with a probability in excess of 99.9%. There is also an uncanny correlation of azimuthal phases between
l = 3 and l = 5. We are unable to blame these effects on foreground contamination or large-scale systematic errors. We show how this reappraisal may be crucial in identifying the theoretical model
behind the anomaly

 

[meteor]

The text mentions that one of the possible explanations for the "axis of evil" could be anisotropic expansion. I think that anisotropic expansion means that the rate of expansion is not the same in all directions, but instead there are directions in which the Universe is expanding faster. Then Kate and Joao say that anisotropic expansion can be due to the effects of strings (cosmic strings, those very large topological deffects, not the tiny strings of string theory), or also be due to walls (I think that they mean domain walls). How can cosmic strings explain anisotropic expansion? Cosmic strings are known to exert repulsive gravity, but I can't fathom how could them cause anisotropic expansion

 

[wolram]

I posted a link some time ago that threw doubt about cosmic strings
existence, I am not sure if they are still in vogue, maybe they are.

 

[wolram]

http://arxiv.org/pdf/astro-ph/0501590
The Rise and Fall of the Cosmic String Theory for Cosmological
Perturbations
L. Perivolaropoulosa*
aDivision of Theoretical Physics, Department of Physics,
University of Ioannina, 451 10 Ioannina, Greece
The cosmic string theory for cosmological fluctuations is a good example of healthy scientific progress in cosmology. It is a well defined physically motivated model that has been tested by cosmological observations and
has been ruled out as a primary source of primordial fluctuations. Until about fifteen years ago, the cosmic string theory of cosmological perturbations provided one of the two physically motivated candidate theories for the
generation of primordial perturbations. The cosmological data that appeared during the last decade have been compared with the well defined predictions of the theory and have ruled out cosmic strings as a primary source
of primordial cosmological perturbations. Since cosmic strings are predicted to form after inflation in a wide range of microphysical theories including (supersymmetric and fundamental string theories) their observational
bounds may serve a source of serious constraints for these theories. This is a pedagogical review of the historical development, the main predictions of the cosmic string theory and the constraints that have been imposed on it
by cosmological observations. Recent lensing events that could be attributed to lighter cosmic strings are also discussed.
I posted it in LQG STRINGS.

 

[meteor]

I posted a link some time ago that threw doubt about cosmic strings
existence, I am not sure if they are still in vogue, maybe they are.

There's a theory called Brane inflation in which cosmic strings are copiously produced during the collision of the two branes, according to this paper
http://arxiv.org/abs/hep-th/0501099

Though, in my personal opinion, cosmic strings are of very doubtable existence. Maybe you know that there are two competing theories to explain the seeds that prompted the formation of galaxies. One is the inflationary scenario, the other postulates that the seeds were induced by topological deffects (e.g. cosmic strings). All the WMAP data seems to favour inflation