Fully relativistic, cosmological N-body simulations

Click For Summary

Discussion Overview

The discussion centers on the potential for fully relativistic cosmological N-body simulations, contrasting them with current Newtonian-based approaches. Participants explore the implications of relativistic effects, particularly in relation to backreaction studies and their influence on cosmological expansion.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation

Main Points Raised

  • Some participants suggest that current N-body simulations neglect relativistic effects and propose that fully-relativistic simulations could provide insights into backreaction effects that might mimic accelerated expansion.
  • Others question the necessity of fully relativistic simulations, arguing that including only the lowest order corrections to Newtonian gravity may suffice and that the computational cost of full relativistic treatment could be prohibitive.
  • A participant expresses skepticism about the validity of backreaction arguments and notes that these effects are generally not considered significant within the community, especially on scales smaller than the Hubble volume.
  • There is a call for references or literature on the topic, indicating a lack of existing work in the area of fully relativistic N-body simulations.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the necessity or feasibility of fully relativistic simulations, with some advocating for their exploration while others express skepticism regarding their relevance and practicality.

Contextual Notes

Participants highlight the challenges of simulating relativistic effects, particularly in the context of merging black holes and the potential computational demands of such simulations. There is also mention of the scale limitations of current simulations and the implications for understanding cosmological phenomena.

Who May Find This Useful

Researchers and students interested in cosmology, gravitational physics, and computational simulations may find this discussion relevant, particularly those exploring the interplay between general relativity and cosmological structure formation.

matt8282
Messages
5
Reaction score
0
Hi,

as you all know, current cosmological N-body simulations (like the Millenium run) are based on the Newtonian limit. Gravitational fields are supposed to be rather weak and therefore the force between dark matter particles reduces to Newtonian gravity. Other relativistic effects are neglected. The cosmological background expands independently of the non-linear processes inside the simulation box. In connection with backreaction studies it might be very useful to have fully-relativistic cosmological N-body simulations. I know that it is extremely difficult to simulate only two merging black holes with all relativistic effects so N-body codes might be completely out of reach. But still, I am interested in this topic. I am not aware of any work on this field.

Can anybody recommend me any article, paper, book or whatsoever? Any source of information is welcome.

Thank you very much in advance!

Best wishes,

Matt
 
Space news on Phys.org
What aspects do you think would require non-linear treatment on cosmological scales?
 
Well, I don't really have a strong opinion on that. But there are claims that backreaction effects could mimic accelerated expansion (see Buchert, for instance) and standard N-body simulations suppress these effects by construction. So that's why I think it would be nice to check that in fully relativistic simulations (if possible..).

Again, any references concerning this are very welcome!
 
The backreaction arguments, and associated large-scale inhomogenous concepts, have never been at all convincing to me---but I certainly don't understand them well enough to have a solid opinion. They are certainly not given much credence in the community.

In any case, these effects are only appreciable on scales comparable to the Hubble volume! Just about all long-duration cosmological structure formation simulations are entirely sub-Gpc scale... I just don't see any GR nonlinearities having any effect in that regime.
 
Why fully relativistic? Surely you really don't need all that extra computation, and any kind simulation would be prohibitively expensive. The next step would presumably just be to include the lowest order corrections to Newtonian gravity, although I suspect these terms are neglected for a good reason ;)
 

Similar threads

Graduate N-body simulation with varying neutrino mass
  • · Replies 1 ·
Replies
1
Views
1K
Undergrad What are P03 procedures or guidelines?
  • · Replies 3 ·
Replies
3
Views
2K
Undergrad What is the purpose of cosmological simulations in understanding dark matter?
  • · Replies 3 ·
Replies
3
Views
2K
Graduate Implications of Symmetry and Pressure in Friedmann Cosmology
  • · Replies 2 ·
Replies
2
Views
2K
Graduate Why isn't back-reaction receiving more study?
  • · Replies 18 ·
Replies
18
Views
4K
Graduate How have N Body simulations solved the missing satellite problem in ΛCDM?
  • · Replies 1 ·
Replies
1
Views
2K
Undergrad Are two-body orbits with a cosmological constant unstable?
  • · Replies 26 ·
Replies
26
Views
3K
Undergrad I made an N-body simulation program
  • · Replies 2 ·
Replies
2
Views
3K
High School Just how Powerful is Computer Science + Astrophysics?
  • · Replies 3 ·
Replies
3
Views
2K
Cosmology Book for someone new to N-Body Simulations
  • · Replies 2 ·
Replies
2
Views
3K