[ExI] dark energy and CMB variations

BillK pharos at gmail.com
Fri Aug 8 08:24:26 UTC 2008

On Thu, Aug 7, 2008 at 10:14 PM, Damien Broderick wrote:
> http://arxiv.org/abs/0805.2974
> Dark Energy Detected with Supervoids and Superclusters
> Abstract: The observed apparent acceleration of the universe is usually
> attributed to negative pressure from a mysterious dark energy. This
> acceleration causes the gravitational potential to decay, heating or cooling
> photons travelling through crests or troughs of large-scale matter density
> fluctuations. This phenomenon, the late-time integrated Sachs-Wolfe (ISW)
> effect, has been detected, albeit at low significance, by cross-correlating
> various galaxy surveys with the Cosmic Microwave Background (CMB). Recently,
> the best evidence has come from the statistical combination of results from
> multiple correlated galaxy data sets. Here we show that vast structures
> identified in a galaxy survey project an image onto the CMB; stacking
> regions aligned with superclusters produces a hot spot, and supervoids, a
> cold spot. At over 4 sigma, this is the clearest evidence of the ISW effect
> to date. For the first time, our findings pin the effect to discrete
> structures. The ISW signal from supervoids and superclusters can be combined
> with other cosmological probes to constrain dark energy and cosmological
> parameters. In addition, our findings make it more plausible that the
> extreme Cold Spot and other anomalies in the CMB are caused by supervoids.

Yes, but there is still much discussion about this frontiers of science area.

We're early in the game on this, but a haze of this material would
clearly have effects on the way light passes through space. Type 1a
supernovae have been considered to be 'standard candles,' their
brightness offering a useful gauge of their distance. It was
observations of particular Type 1a supernovae whose light was believed
to be dimmer than it ought to have been at near infrared wavelengths
that in the 1990's helped to shape the accelerated expansion theory.

But if these supernovae are dimmer than expected, accelerated
expansion is but one explanation. An alternative in the form of some
kind of intervening material has long been suggested as a solution,
but evidence for graphite whiskers has never been confirmed until now.


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