Congratulations to Christine on the new paper

[marcus]

just posted today
http://arxiv.org/abs/astro-ph/0604544
Energy Ranking Preservation in a N-Body Cosmological Simulation
Christine C. Dantas (IAE/CTA, Brazil), Fernando M. Ramos (LAC/INPE, Brazil)
8 pages, 3 figures, accepted for publication in the MNRAS

"In this paper we present a study of the cosmic flow from the point of view of how clusterings at different dynamical regimes in an expanding universe evolve according to a `coarse-grained' partitioning of their ranked energy distribution. By analysing a Lambda-CDM cosmological simulation from the Virgo Project, we find that cosmic flows evolve in an orderly sense, when tracked from their coarse-grained energy cells, even when nonlinearities are already developed. We show that it is possible to characterize scaling laws for the Pairwise Velocity Distribution in terms of the energy cells, generally valid at the linear and nonlinear clustering regimes."

Christine has sometimes joined the discussion here in the "Beyond" forum. And she has a blog "Background Independence"
http://christinedantas.blogspot.com/
that follows her interests including Quantum Gravity, Cosmology, and Astrophysics.

 

[josh1]

Would someone please move this thread. It has nothing whatsoever to do with the subject of this forum.

 

[Chronos]

It's categorized under HEP in arxiv, Josh1. This is where we usually discuss such papers.

 

[SpaceTiger]

So at what scales do we expect energy ranking preservation to break down? Surely, for systems that are collisional, two-body interactions should mix the particles too effectively for ERP, but what about violent relaxation? Are there realistic situations in which we expect it to be more effective at mixing of the particles in phase space?

 

[ccdantas]

Thanks, Marcus, for bringing out my recent paper for discussions here. However, I think josh1 is right, it does not have anything to do with the topic "Beyond the Standard Model". The paper deals with Newtonian gravitation...

It would of course be quite interesting if the behaviour we see in N-body gravitational simulations remains valid at higher and higher energies and smaller and smaller scales...

SpaceTiger: in collisionless gravitational systems, "violent relaxation" is probably not so violent, or if so, it is incomplete. See the paper for references. Concerning the scale at which ERP breaks down, in our astro-ph/0508488 we have tried to find it from Arnold´s theorem, but much more work need to be done, it still somewhat inconclusive.

Best wishes
Christine

 

[marcus]

Thanks, Marcus, for bringing out my recent paper for discussions here...

I wish to congratulate you on the paper, and boost your blog, Christine.

Since you were just having a serious discussion with a few other young researchers here at "Beyond" forum, I decided to post congratulations here where you might see it, instead of in "astrophysics" forum where you might not AFAIK ever visit.

I am glad SpaceTiger happened to comment. He is a grad student in cosmology at Princeton (there is a remote chance you may have run into him professionally or that you both know some of the same people)

About your blog, I want to mention that in case some readers don't know it is one of a small growing NETWORK of QG-related blogs

there is yours (which combines QG, cosmo, and astrophysics)
and Alejandro Satz (who studies QG in UK)
http://realityconditions.blogspot.com/
and Victor Rivelles (a faculty with QG research interests)
and Sabine H. (QG and string pheno among several other interests)

And several others. If anyone who comes here to "Beyond" forum and is interested in QG wants to check out some related blogs they can visit yours and your blog list can refer them to the others.

Ooops, I see that you currently do not have link to Victor Rivelles "Sum over Histories" blog, so i will put it here.
http://rivelles.blogspot.com/
It is bilingual and the self-description is:
"News on quantum gravity, strings and other interesting stuff in physics.
Novidades em gravitação quântica, cordas e outras coisas interessantes em física."

BTW if anyone would like to DISCUSS Christine's new paper, why not start a thread about it in Astrophysics forum?

 

[josh1]

...I decided to post congratulations here where you might see it...

This is what the private messenging system is for, and I think you know this.

 

[selfAdjoint]

This is what the private messenging system is for, and I think you know this.

Let's get off this topic. If anything is OT this whole subject is.

 

[josh1]

Respectfully SelfAdjoint,

I do think it's very important that the posting guidelines of PF be respected in every possible way and the responsibility of members to ensure they are as long as they act within the guidelines.

Let's get off this topic. If anything is OT this whole subject is.

Does this mean you agree or disagree?

 

[SpaceTiger]

SpaceTiger: in collisionless gravitational systems, "violent relaxation" is probably not so violent, or if so, it is incomplete.

Yes, I found that fact especially interesting, since I'm studying structures in the non-linear regime (filaments). Would you say the lack of mesoscopic mixing lends hope to the possibility of reconstructing the initial conditions for filamentary structures on the scales you're exploring?

See the paper for references. Concerning the scale at which ERP breaks down, in our astro-ph/0508488 we have tried to find it from Arnold´s theorem, but much more work need to be done, it still somewhat inconclusive.

ERP seems to be strongly violated in the low-mass end of the regime you tested (~10^{13} solar). Do you not trust this result? Are you concerned about effects coming from the finite resolution of the N-Body simulation?

The fact that phase space mixing kicks in before mesoscopic mixing seems to suggest that we're still seeing deterministic behavior after the shells cross. Is the behavior of the large scale structure self-similar in the ERP?

 

[josh1]

...josh1 is right, it does not have anything to do with the topic "Beyond the Standard Model". Best wishes
Christine

Why are Christine's wishes not being respected?

 

[marcus]

I have PM'd my consent for this thread to move to one of the Astronomy fora, if that is what the mods decide to do.

that is fine with me. Discussion on a technical level might belong in Astrophysics or in Cosmology.

from a human standpoint, I am proud of the fact that several young researchers we are acquainted with through their participation here at Beyond forum (and not-so-young too) are PUBLISHING

I think when you have been having a conversation with someone, and you find out they just posted on arxiv, or published hardcopy, then it's right to ACKNOWLEDGE that, and publicly congratulate 'em.

And it is good for other Beyond forum posters to know that. I don't want to be talking to someone as if they hadnt just published---it's to celebrate!

So I have done that several times. In the case of Sabine H. and Jim Graber, and arivero, and Christine.
And actually I think others.

If somebody is one of us, and they get an appointment or post a research paper, we should take notice.
It is the being one of us, combined with the professional activity, that makes it topical.

But after saying congratulations Christine!, I don't mind wherever the thread goes. Cosmology might be good.

BTW it's an interesting paper! They are strong at using the computer in massive numerical simulations!
Have fun all.

 

[selfAdjoint]

Since both the originator of the thread, Marcus, and its dedicatee, Christine, are agreed, I will move the thread to Astrophysics.

 

[Chronos]

I'm going to revert to a point Hossi made in her recent paper; how does this preserve causality in communications between independent observers?