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  #151 (permalink)  
Old 03-September-2007, 05:35 AM
chriscurtis chriscurtis is offline
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> The problem can probably be fixed by ascribing another parameter to dark energy.

Talking of which, what is minimum amount of parameters needed for to create a universe for the standard model and gravity?

As a software designer, I would love to model the Universe starting a line with one 'dot' on it over time. Then two dots, then three dots, then a plane, adding dimensions and properties to see what happens during this process.

This would mean a cut down in Facebook time (but not bautforum).
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  #152 (permalink)  
Old 03-September-2007, 06:15 PM
William William is offline
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Default GRW Generation & Detection

In reply to Ken G.'s #148

Quote:
But the Big Bang was never expected to yield detectable gravity waves, it's hard enough to see the CMB! I presume they are talking about indirect influences of gravity waves like seeding structure.
Ken,

No. I believe there are theories that have mechanisms that generate detectable GRW during the hypothesized early universe processes. I believe inflation requires its own very, very, large energy source (independent of BB). I assume the hypothesized inflation event has some impact on space-time, in the models.

The following is the excerpt from the 91 page paper, I was referring to.

(WMAP) Three Year Observations: Implications for Cosmology, by 21 authors.

http://xxx.lanl.gov/pdf/astro-ph/0603449

Page 45:

Quote:
For power law inflationary models, this suggests a detectable level of gravity waves. There are, however, many inflationary models that predict a much smaller gravity wave amplitude. Alternative models, such as the ekpyrotic scenario (Khoury et al. 2001, 2002) also predict an undetectable level of gravity waves.
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I believe that GRW do not exist, so I am interested in the outcome of the GRW detection experiments.

A result of GRW not existing would be that space should be absolutely flat.
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  #153 (permalink)  
Old 04-September-2007, 01:26 AM
Fortunate Fortunate is offline
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http://adsabs.harvard.edu/abs/2003dume.symp..162K discusses, among other things, the prospects of the Planck satellite's detecting gravitational waves.

"If inflation took place at an energy scale much smaller than that of grand unification, then the signal will be too small to be detectable. However, if inflation had something to do with grand unification or Planck-scale physics, then the signal is conceivably detectable in the optimistic case by the Planck satellite...."

This article was written in 2003.
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  #154 (permalink)  
Old 04-September-2007, 04:26 AM
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Quote:
Originally Posted by chriscurtis View Post
Jerry, I am a big fan. I think you ask the questions a lot of people are thinking. Well, at least me anyway :-) I don't mind dark matter or energy, but I do get the feeling we don't understand how gravity works on a large scale. I also get the feeling that the neutrino has a lot more to do with what's going on than it is letting on. Perhaps I read Newscientist too much.

Can this void be observational evidence against dark energy or dark matter?
I don't see how or why an actual void in the local cosmos would produce a lower temperature than a properly-corrected full-sky survey. The void seems to me to have a rather nullifying effect upon all of the science drawn from CMB observations; but oddly, not necessarily upon the root theories.

The current interpretations assume all of the local radio background noise can be properly corrected for by studying other spectral signatures. When we look any direction in space, some of these signatures overlap, and seeing a void this size is a little like eyeballing into the center of a bicycle hub from the rim and not seeing any spokes connecting the rim to the hub. The corrections for ISW effects do not predict this type of void. It means the corrections are wrong, the structure is not what was used in the models.

If gravity is not understood, then neither of the dark stuff theories stand: They are both the product of gravity not behaving as expected: Observations we have made are different than expected on the bases of relativistic gravity and a big bang event prior to our studies of galactic behavior. The dark matter and dark energy solutions are whole dependant upon the curret understanding of gravity being the correct one.
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  #155 (permalink)  
Old 04-September-2007, 01:54 PM
Fortunate Fortunate is offline
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Quote:
Originally Posted by Jerry View Post
I don't see how or why an actual void in the local cosmos would produce a lower temperature than a properly-corrected full-sky survey.
According to the links provided by Cougar in post #37 on this thread, in the absence of dark energy, the void would not cause a cold spot. In an energy-dominated universe, however, the so-called "late integrated Sachs-Wolfe effect" kicks in and causes the photons to lose energy as they pass through the void. I'm not claiming this myself (my understanding of late ISW is vague) - I'm just pointing to articles that say so.
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  #156 (permalink)  
Old 04-September-2007, 02:32 PM
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Default The Too late integrated Sachs-Wolf effect

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Originally Posted by Fortunate View Post
According to the links provided by Cougar in post #37 on this thread, in the absence of dark energy, the void would not cause a cold spot. In an energy-dominated universe, however, the so-called "late integrated Sachs-Wolfe effect" kicks in and causes the photons to lose energy as they pass through the void. I'm not claiming this myself (my understanding of late ISW is vague) - I'm just pointing to articles that say so.
I don't see how this could be a viable solution. In order to explain the power function of the CMB, DE must be uniformely distributed: All CMB photons entering local space must do so at the same temperature, and loose calories at the same rate. If photons wiggling through local structure are warmer than photons presented through a local void, the most reasonable solution is that signature of the background is thermally compromised as it passes through the local structure. It is not reasonable to assume the photons presented to the void were cooler in the first place. That requires a new parameter, adherance to a model at all costs, and that is very bad science.
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  #157 (permalink)  
Old 06-September-2007, 09:37 PM
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Here's the authors' website about the Void:
http://webusers.astro.umn.edu/~larry/void

Last edited by pumpkinpie; 07-September-2007 at 05:18 PM.
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  #158 (permalink)  
Old 07-September-2007, 02:29 AM
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Quote:
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Is there any offical theories of why this hole is so large? Has phil plait said anything about it?
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  #159 (permalink)  
Old 07-September-2007, 09:43 AM
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Question- could this be an amplified result of one of the irregularities in the hypothesized original singularity, that has expanded into a huge region as the original singularity expanded into an even huger universe?
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  #160 (permalink)  
Old 07-September-2007, 10:52 AM
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Quote:
Originally Posted by Intenceman View Post
could this be an amplified result of one of the irregularities in the hypothesized original singularity
If there was a singularity, it didn't have irregularities, but odds are that this feature got started very early in the universe's development.
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  #161 (permalink)  
Old 08-September-2007, 06:46 AM
JIM WALKER JIM WALKER is offline
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Cool Hole In The Universe

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Originally Posted by Mayonaze View Post
I suppose this is where all my odd socks have been going ...
dont blame me , i didn,t wear them jim
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  #162 (permalink)  
Old 11-September-2007, 06:57 AM
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Originally Posted by antoniseb View Post
If there was a singularity, it didn't have irregularities, but odds are that this feature got started very early in the universe's development.
Thank you for taking the time to answer. I have a heck of a lot to learn here.
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  #163 (permalink)  
Old 12-October-2007, 10:40 PM
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When growing up--before I learned the universe had no center--I always envisioned something like this being at the center...
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  #164 (permalink)  
Old 13-October-2007, 01:57 AM
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God: "Darn, I knew I missed a spot!"
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  #165 (permalink)  
Old 29-October-2007, 05:00 PM
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Some posters earlier had inquired about the shape of the void. I attended a talk given by Dr. Rudnick this weekend, and I asked that question. His response: from calculations they determined the characteristic volume of a sphere with a diameter of 1 billion light years. They do not know the actual shape, but that is their assumption for the purpose of their research.
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  #166 (permalink)  
Old 29-October-2007, 05:12 PM
Fortunate Fortunate is offline
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Quote:
Originally Posted by pumpkinpie View Post
Some posters earlier had inquired about the shape of the void. I attended a talk given by Dr. Rudnick this weekend, and I asked that question. His response: from calculations they determined the characteristic volume of a sphere with a diameter of 1 billion light years. They do not know the actual shape, but that is their assumption for the purpose of their research.
Thanks.
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  #167 (permalink)  
Old 12-May-2008, 03:51 AM
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Quote:
Originally Posted by Doodler View Post
Bmpbmp, also consider, even though this is a big hole in space, its not a hole in the sense of a puncture in anything, its more of a hole in the sense of a bubble in a pot of boiling water.

There's no evidence to say that there was ever anything there to be sucked up in any event, its more likely just the result of unevenly distributed matter in the universe.
Is there any evidence that the expansion of space has effected this region more than others? Thought being that there is more non-gravitationally bound space there than anywhere else.
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  #168 (permalink)  
Old 13-May-2008, 09:05 PM
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Default Woo Hoo! I knew they'd find The Holey One

My religion is proven! Repent, all of you!

By way of explanation: once upon a long time ago I and several other students from my 500-level set theory class founded The Church of the Holy Nullity. I'm a Cardinal of the Church (members are either Cardinal or Ordinals).

Why the Nullity? Well, in the Beginning was the Null set. And the Null Set begat the universe of discourse.

More seriously, this is a very cool thing to find. I suspect that study of the large scale structure of the (physical) universe will, in the end, lead to some very significant surprises.
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  #169 (permalink)  
Old 14-May-2008, 05:52 PM
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Um, never mind:

Huge hole in the cosmos disappears

Quote:
Now you see it, now you don’t. A giant hole in the cosmos that shocked astrophysicists last year may not exist after all. A re-examination of the area has found that the 'void', which supposedly contained far fewer stars and galaxies than expected, could be a statistical artefact.
From a New Scientist story.
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  #170 (permalink)  
Old 14-May-2008, 06:12 PM
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Quote:
Originally Posted by ToSeek View Post
Um, never mind:
Ya know, since this topic was revived, I read (Discoverer) Rudnick's Void FAQ, and had intended to point out this fascinating item:

Quote:
Are there more voids like this?
Probably. Our current surveys of the universe have not yet been of large enough volumes to find voids of this size. First though, it is important that we and other astronomers confirm that the new void is not simply a statistical fluke, and that there are no attractive alternatives to explain the data.
I guess Rudnick saw it coming.
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