Comments on: Where the dark matter is http://blogs.discovermagazine.com/cosmicvariance/2005/12/13/where-the-dark-matter-is/ Random samplings from a universe of ideas. Sun, 14 Mar 2010 08:03:20 -0500 http://wordpress.org/?v=2.8.4 hourly 1 By: Fraser Cain http://blogs.discovermagazine.com/cosmicvariance/2005/12/13/where-the-dark-matter-is/comment-page-1/#comment-8504 Fraser Cain Wed, 14 Dec 2005 23:16:45 +0000 http://blogs.discovermagazine.com/cosmicvariance/2005/12/13/where-the-dark-matter-is/#comment-8504 Okay, I've completed the interview with Dr. Jee. You can access it here: <a href="http://www.universetoday.com/am/publish/podcast_dark_matter_maps.html?14122005" rel="nofollow">Podcast: Dark Matter Maps</a> Okay, I’ve completed the interview with Dr. Jee. You can access it here: Podcast: Dark Matter Maps

]]> By: Plato http://blogs.discovermagazine.com/cosmicvariance/2005/12/13/where-the-dark-matter-is/comment-page-1/#comment-8503 Plato Wed, 14 Dec 2005 20:27:18 +0000 http://blogs.discovermagazine.com/cosmicvariance/2005/12/13/where-the-dark-matter-is/#comment-8503 From a <a href="http://eskesthai.blogspot.com/2005/12/second-of-five-lagrangian-equilibrium.html" rel="nofollow">simple</a> generalized view. For those who want to explore the greater potential of space travel, what would lensing tell you about the routes to take? Of course, I am speculating :) From a simple generalized view.

For those who want to explore the greater potential of space travel, what would lensing tell you about the routes to take? Of course, I am speculating :)

]]> By: FP http://blogs.discovermagazine.com/cosmicvariance/2005/12/13/where-the-dark-matter-is/comment-page-1/#comment-8502 FP Wed, 14 Dec 2005 17:46:00 +0000 http://blogs.discovermagazine.com/cosmicvariance/2005/12/13/where-the-dark-matter-is/#comment-8502 This is probably a stupid question. Could the 2d regime be associated with (non-critical) strings ? And even more stupid. Could the 4d reflect some sort of Hausdorff dimension of non-critical strings? This is probably a stupid question.
Could the 2d regime be associated with (non-critical) strings ?

And even more stupid.
Could the 4d reflect some sort of Hausdorff dimension of non-critical strings?

]]> By: Moshe http://blogs.discovermagazine.com/cosmicvariance/2005/12/13/where-the-dark-matter-is/comment-page-1/#comment-8501 Moshe Wed, 14 Dec 2005 16:46:19 +0000 http://blogs.discovermagazine.com/cosmicvariance/2005/12/13/where-the-dark-matter-is/#comment-8501 Jacques, I will be looking forward to that discussion. I am utterly confused about both claims of two-dimensionality. One my usual confusion about measurability: is the spectral dimension a measurable quantity, does it express some property of measurment or series of measurments? it does not seem to be phrased that way. Also, RNG flow interpolating between two and four dimensions seems to me a strange phenomena, contradiciting general intuition about such flows losing degrees of freedom between the UV and the IR. Jacques, I will be looking forward to that discussion. I am utterly confused about both claims of two-dimensionality. One my usual confusion about measurability: is the spectral dimension a measurable quantity, does it express some property of measurment or series of measurments? it does not seem to be phrased that way. Also, RNG flow interpolating between two and four dimensions seems to me a strange phenomena, contradiciting general intuition about such flows losing degrees of freedom between the UV and the IR.

]]> By: Plato http://blogs.discovermagazine.com/cosmicvariance/2005/12/13/where-the-dark-matter-is/comment-page-1/#comment-8500 Plato Wed, 14 Dec 2005 16:31:33 +0000 http://blogs.discovermagazine.com/cosmicvariance/2005/12/13/where-the-dark-matter-is/#comment-8500 Dissident, in context of the future book, I agree:) Dissident,

in context of the future book, I agree:)

]]> By: Dissident http://blogs.discovermagazine.com/cosmicvariance/2005/12/13/where-the-dark-matter-is/comment-page-1/#comment-8499 Dissident Wed, 14 Dec 2005 16:28:11 +0000 http://blogs.discovermagazine.com/cosmicvariance/2005/12/13/where-the-dark-matter-is/#comment-8499 It's indeed disappointing when people exploring different approaches to a problem seem to ignore each other. The public, who's ultimately paying for it all, just might get the idea that those failing to respond have no answers... A debate between Distler and Reuter (and Loll?), now that would be something! As would one between, say, Sean and Cooperstock & Tieu. Why not right here on cosmicvariance? Maybe the recent Krauss guest-blogging/debate invitation could serve as a model? It’s indeed disappointing when people exploring different approaches to a problem seem to ignore each other. The public, who’s ultimately paying for it all, just might get the idea that those failing to respond have no answers…

A debate between Distler and Reuter (and Loll?), now that would be something! As would one between, say, Sean and Cooperstock & Tieu. Why not right here on cosmicvariance? Maybe the recent Krauss guest-blogging/debate invitation could serve as a model?

]]> By: Jacques Distler http://blogs.discovermagazine.com/cosmicvariance/2005/12/13/where-the-dark-matter-is/comment-page-1/#comment-8498 Jacques Distler Wed, 14 Dec 2005 15:36:45 +0000 http://blogs.discovermagazine.com/cosmicvariance/2005/12/13/where-the-dark-matter-is/#comment-8498 <blockquote>On the other hand, if the perturbative truncation Reuter studies really did get the qualitative behavior right, is there some sort of lattice study someone could do to show that it really is true nonperturbatively? Is anyone trying?</blockquote> I have discussed Reuter et al's work with people (whom I otherwise respect greatly), who — despite the obvious objections — continue to be enthusiastic about it because it "agrees" with what is found in the Causal Dynamical Triangulations (CDT) approach. Specifically, the anomalous dimension found by Reuter et al "agrees" with the CDT calculation, indicating that the spectral dimension of spacetime, ds=2, at short distances. (You'll note that those are not, in any obvious way, the same thing, but don't think too hard about that.) I've been meaning to write a blog post discussing of CDT, for a while now. Someday, I'll get around to it.

On the other hand, if the perturbative truncation Reuter studies really did get the qualitative behavior right, is there some sort of lattice study someone could do to show that it really is true nonperturbatively? Is anyone trying?

I have discussed Reuter et al’s work with people (whom I otherwise respect greatly), who — despite the obvious objections — continue to be enthusiastic about it because it “agrees” with what is found in the Causal Dynamical Triangulations (CDT) approach.

Specifically, the anomalous dimension found by Reuter et al “agrees” with the CDT calculation, indicating that the spectral dimension of spacetime, ds=2, at short distances. (You’ll note that those are not, in any obvious way, the same thing, but don’t think too hard about that.)

I’ve been meaning to write a blog post discussing of CDT, for a while now. Someday, I’ll get around to it.

]]> By: a. krug http://blogs.discovermagazine.com/cosmicvariance/2005/12/13/where-the-dark-matter-is/comment-page-1/#comment-8497 a. krug Wed, 14 Dec 2005 15:17:59 +0000 http://blogs.discovermagazine.com/cosmicvariance/2005/12/13/where-the-dark-matter-is/#comment-8497 Jacques, Thanks for taking a look at these papers and saving the rest of some effort in figuring out if they make sense. Your posts are quite useful. The continued claims that beta functions are "nonperturbative" are bizarre. Hasn't anyone pointed out to Reuter that this is just not true? On the other hand, if the perturbative truncation Reuter studies really <i>did</i> get the qualitative behavior right, is there some sort of lattice study someone could do to show that it really <i>is</i> true nonperturbatively? Is anyone trying? -- a. krug Jacques,

Thanks for taking a look at these papers and saving the rest of some effort in figuring out if they make sense. Your posts are quite useful.

The continued claims that beta functions are “nonperturbative” are bizarre. Hasn’t anyone pointed out to Reuter that this is just not true?

On the other hand, if the perturbative truncation Reuter studies really did get the qualitative behavior right, is there some sort of lattice study someone could do to show that it really is true nonperturbatively? Is anyone trying?

– a. krug

]]> By: Jacques Distler http://blogs.discovermagazine.com/cosmicvariance/2005/12/13/where-the-dark-matter-is/comment-page-1/#comment-8496 Jacques Distler Wed, 14 Dec 2005 14:29:37 +0000 http://blogs.discovermagazine.com/cosmicvariance/2005/12/13/where-the-dark-matter-is/#comment-8496 <blockquote>Jacques, I didn't want to invoke you in vain, but my first thought upon seeing http://arxiv.org/abs/hep-th/0511260 was actually "aha, retort!"...</blockquote> Then you, like me, eagerly downloaded it, and read it through. And then, disappointed, you scratched your head and went back to whatever it was you had been doing ...

Jacques, I didn’t want to invoke you in vain, but my first thought upon seeing http://arxiv.org/abs/hep-th/0511260 was actually “aha, retort!”…

Then you, like me, eagerly downloaded it, and read it through.

And then, disappointed, you scratched your head and went back to whatever it was you had been doing …

]]> By: Centauri Dreams » Blog Archive » ‘Seeing’ Dark Matter http://blogs.discovermagazine.com/cosmicvariance/2005/12/13/where-the-dark-matter-is/comment-page-1/#comment-8495 Centauri Dreams » Blog Archive » ‘Seeing’ Dark Matter Wed, 14 Dec 2005 14:04:46 +0000 http://blogs.discovermagazine.com/cosmicvariance/2005/12/13/where-the-dark-matter-is/#comment-8495 [...] The team’s findings appear as Jee, White, Ford et al., “Hubble Space Telescope Advanced Camera for Surveys Weak-Lensing and Chandra X-Ray Studies of the High-Redshift Cluster MS 1054-0321,” Astrophysical Journal 634 (December 1, 2005). An abstract is available here. 12/14 update: Cosmic Variance has been carrying on an interesting discussion on these findings. [...] [...] The team’s findings appear as Jee, White, Ford et al., “Hubble Space Telescope Advanced Camera for Surveys Weak-Lensing and Chandra X-Ray Studies of the High-Redshift Cluster MS 1054-0321,” Astrophysical Journal 634 (December 1, 2005). An abstract is available here. 12/14 update: Cosmic Variance has been carrying on an interesting discussion on these findings. [...]

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