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"Dark Energy" model of accelerated universe expansion gains



 
 
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  #1  
Old February 3rd 09, 09:07 AM posted to sci.astro.research
Jonathan Thornburg[_4_]
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Posts: 15
Default "Dark Energy" model of accelerated universe expansion gains

From: "Jonathan Thornburg [remove -animal to reply]"
Subject: "Dark Energy" model of accelerated universe expansion gains support
Newsgroups: sci.astro.research
References:

Kent Paul Dolan wrote:
The support is mostly of the "eliminating alternatives
one by one" sort, but it's still of interest.

http://www.physorg.com/news152374990.html


For more details, see
http://link.aps.org/doi/10.1103/PhysRevLett.101.251303
(subscription required, alas), or
http://arxiv.org/abs/0809.3761

Authors:
James P. Zibin, Adam Moss, and Douglas Scott
Title:
Can We Avoid Dark Energy?
Abstract:
The idea that we live near the center of a large, nonlinear void
has attracted attention recently as an alternative to dark energy
or modified gravity. We show that an appropriate void profile can
fit both the latest cosmic microwave background and supernova
data. However, this requires either a fine-tuned primordial
spectrum or a Hubble rate so low as to rule these models out. We
also show that measurements of the radial baryon acoustic scale
can provide very strong constraints. Our results present a serious
challenge to void models of acceleration.

--
-- "Jonathan Thornburg [remove -animal to reply]"
Dept of Astronomy, Indiana University, Bloomington, Indiana, USA
"Washing one's hands of the conflict between the powerful and the
powerless means to side with the powerful, not to be neutral."
-- quote by Freire / poster by Oxfam
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  #2  
Old February 8th 09, 09:35 AM posted to sci.astro.research
Eric Flesch
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Posts: 321
Default "Dark Energy" model of accelerated universe expansion gains support

The subject header is unfounded. The void bubble scenario is just a
mathematician's sandbox, saying "how can we account for observations
by manipulating a physical model, however unlikely". One person
builds a sand castle, the next person kicks it down. This sort of
mathematics-based activity is inevitable considering that dark energy
itself is exactly such a sandbox model, modelling that the universe
itself does unintuitive physical things to satisfy the current state
of observations.

Challenges to dark energy will come from outside the sandbox, where
processes other than dynamical expansion are entertained. We're just
in the flat-Earth stage of cosmology right now, I posit.

Eric


On 03 Feb 09, Jonathan Thornburg wrote:
Kent Paul Dolan wrote:
The support is mostly of the "eliminating alternatives
one by one" sort, but it's still of interest.

Abstract: ...
Our results present a serious
challenge to void models of acceleration.

  #3  
Old February 8th 09, 02:07 PM posted to sci.astro.research
Phillip Helbig---remove CLOTHES to reply
external usenet poster
 
Posts: 198
Default "Dark Energy" model of accelerated universe expansion gains support

In article ,
(Eric Flesch) writes:

The subject header is unfounded. The void bubble scenario is just a
mathematician's sandbox, saying "how can we account for observations
by manipulating a physical model, however unlikely". One person
builds a sand castle, the next person kicks it down. This sort of
mathematics-based activity is inevitable considering that dark energy
itself is exactly such a sandbox model, modelling that the universe
itself does unintuitive physical things to satisfy the current state
of observations.

Challenges to dark energy will come from outside the sandbox, where
processes other than dynamical expansion are entertained. We're just
in the flat-Earth stage of cosmology right now, I posit.


While I personally don't agree that we are still in the flat-Earth stage
of cosmology, I also think that dark energy (or smooth tension, or the
cosmological constant) is the best description for what's going on. The
void bubble is a mathematician's sandbox. However, I think it is
important to discuss such "alternative scenarios", whether or not the
person who puts them forward sees himself as a devil's advocate or not.
Jim Peebles put forward many alternative scenarios which were a)
compatible with the data known when they were put forward and b) made
testable predictions. All were falsified when the (usually CMB) data
became better. But they were useful since they pointed out the
difference between "model A is compatible with the current data, but so
is model B" (correct) and "the data imply model A" (incorrect, at least
without additional data or assumptions).
 




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