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Post Info TOPIC: WMAP Cold Spot
Blobrana


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RE: WMAP Cold Spot
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Title: In defence of local textures (and other Higgs gradients)
Authors: Tommy Anderberg

Cruz et al. recently showed that the CMB cold spot can be explained by a GUT-scale texture. But following Turok's argument that gauged configurations always relax quickly, they posit a global symmetry, without obvious relation to GUTs. An observation by Nambu invalidates Turok's argument when the broken symmetry group has commuting generators. This is demonstrated explicitly in the standard model of electroweak interactions and holds generally for intermediate SSB stages in GUTs. The cold spot could therefore be due to a GUT texture, and electroweak Higgs gradients may evolve indefinitely.

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Blobrana


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Eridanus Cold Spot
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Scientists think that shortly after the Big Bang, as the universe cooled and expanded, exotic particles transformed into the particles we know today via phase transitions similar to the gas-liquid-solid transitions that matter now experiences on Earth.
And like phase transitions on Earth, defects inevitably occur. When water crystallises to ice, for example, cloudy spots appear in the ice that mark where water molecules are misaligned. Physicists predict that similar defects happened during the phase transitions of the early universe, and that the defects took different forms.
The team thinks a cold spot in the cosmic microwave background (CMB) an energy artefact of the Big Bang that has been detected and mapped by NASA's Wilkinson Microwave Anisotopy Probe (WMAP) satelliterepresents the most complex kind of cosmic defect, a 3-D blob-like structure called a texture.
Marcos Cruz of the Instituto de Fisica de Cantabria in Spain and colleagues analysed the CMB cold spot, which spans 1 billion light-years across, finding it had properties consistent with a texture.

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Blobrana


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RE: WMAP Cold Spot
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It is a hole that could hardly be hidden by moving the sofa. Radio astronomers have found a gigantic void in the universe, which at nearly a billion light years across is the biggest ever seen. Apparently empty of both normal matter and dark matter, the finding challenges theories of large-scale structure formation.

The finding challenges theories of large-scale structure formation

Lawrence Rudnick and colleagues at the University of Minnesota in Minneapolis were studying data from a survey carried out by the Very Large Array radio telescope in New Mexico - in particular a "cold spot" in the map of the cosmic microwave background, or CMB. In this spot, which lies in the direction of the constellation Eridanus, the CMB photons are colder than expected.

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Hole.kmz
Google Sky File

-- Edited by Blobrana at 15:21, 2008-01-12

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Blobrana


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HOLE_ge1
The blue zone in this image represents an unexplained empty zone in the universe about 1 billion light-years wide.
Credit: NRAO

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Blobrana


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could be anywhere...
Expand (kb, 800 x 600)

Ed - it seems that the Question mark symbol indicates the position of the `WMAP Cold Spot`.

-- Edited by Blobrana at 23:04, 2007-08-24

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Blobrana


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Astronomers have found an enormous void in space that measures nearly a billion light-years across.
It is empty of both normal matter - such as galaxies and stars - and the mysterious "dark matter" that cannot be seen directly with telescopes.
The "hole" is located in the direction of the Eridanus constellation and has been identified in data from a survey of the sky made at radio wavelengths.

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Blobrana


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Astronomers have found an enormous hole in the Universe, nearly a billion light-years across, empty of both normal matter such as stars, galaxies, and gas, and the mysterious, unseen "dark matter." While earlier studies have shown holes, or voids, in the large-scale structure of the Universe, this new discovery dwarfs them all.

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The spot, which was first found in the WMAP 1-year data at position (b = 57°, l = 209°) and subtending 10° in the sky, has been now confirmed with the WMAP 3-year data.

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Blobrana


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The universe has a huge hole in it that dwarfs anything else of its kind. The discovery caught astronomers by surprise.
The hole is nearly a billion light-years across. It is not a black hole, which is a small sphere of densely packed matter. Rather, this one is mostly devoid of stars, gas and other normal matter, and it's also strangely empty of the mysterious "dark matter" that permeates the cosmos. Other space voids have been found before, but nothing on this scale.
The region had been previously been dubbed the "WMAP Cold Spot," because it stood out in a map of the Cosmic Microwave Background (CMB) radiation made by NASA's Wilkinson Microwave Anisotopy Probe (WMAP) satellite.

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Title: Local Voids as the Origin of Large-angle Cosmic Microwave Background Anomalies: The Effect of a Cosmological Constant
Authors: Kaiki Taro Inoue, Joseph Silk
(Version v2)

We explore the large angular scale temperature anisotropies in the cosmic microwave background (CMB) due to homogeneous local dust-filled voids in a flat Friedmann-Robertson-Walker universe with a cosmological constant. In comparison with the equivalent dust-filled void model in the Einstein-de Sitter background, we find that the anisotropy for compensated asymptotically expanding local voids can be larger because second-order effects enhance the linear integrated Sachs-Wolfe (ISW) effect. However, for local voids that expand sufficiently faster than the asymptotic velocity of the wall, the second-order effect can suppress the fluctuation due to the linear ISW effect. A pair of quasi-linear compensated asymptotic local voids with radius (2-3)*10^2 ~h^{-1} Mpc and a matter density contrast ~-0.3 can be observed as cold spots with a temperature anisotropy Delta T/T~O(10^{-5}) that might help explain the observed large-angle CMB anomalies. We predict that the associated anisotropy in the local Hubble constant in the direction of the voids could be as large as a few percent.

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