<p>If you can provide examples of numerical methods in GR you've seen/heard of that would help focus the question.</p>

<p>From the article you linked to: "The technique keeps track of a vast number of quarks and gluons by describing the space and time inside a proton with a set of points that make up a 4D lattice". This almost gets to the main issue with Numerical Relativity. There is no natural computational grid on which to simulate space-time. The whole game with GR is that gravity is space-time so first you have to simulate the space-time and then you have to simulate the objects (neutron stars, black holes, gravitational waves) on top. </p>

<p>As the links below go into, its very difficult to create a consistent computational grid since the physical space-time your trying to simulate for a black hole has "funny" things in it like singularities, or an event horizon pas which we can't really know what's going on. </p>

<p>I think this article: <a href="http://astronomy.com/magazine/2016/02/putting-einstein-to-the-test?page=1" rel="nofollow">http://astronomy.com/magazine/2016/02/putting-einstein-to-the-test?page=1</a></p>

<p>does a good job of summing up the field, and its quite accessible.</p>

<p>For something more rigorous please see: <a href="http://arxiv.org/pdf/1010.5260v2.pdf" rel="nofollow">http://arxiv.org/pdf/1010.5260v2.pdf</a>
That paper gets into some of the math behind the article linked to above.</p>

CC BY-SA 3.0
2016-04-28T14:33:34.827Z
2016-04-28T14:33:34.827Z
tau1777
<p>As I know, for example the modelling of the collapse of a neutron star (to a black hole) wasn't done correctly until now.</p>

<p>Why? Yes, I know, the Einstein Field Equations aren't really easy to solve. But, for example, the situation is very similar in the case of the QCD, but there are already fruitful results existing ( <a href="http://physicsworld.com/cws/article/news/2008/nov/21/proton-and-neutron-masses-calculated-from-first-principles">http://physicsworld.com/cws/article/news/2008/nov/21/proton-and-neutron-masses-calculated-from-first-principles</a> ).</p>

<p>Is there any theoretical obstacle in the way? Or we simply didn't have enough fast computers/physicist/programmer manyear until now?</p>

CC BY-SA 3.0
2014-09-16T15:12:03.870Z
Can you give more details about the model you have found?
HDE 226868
CC BY-SA 3.0
2014-09-16T16:36:50.303Z
Perhaps, this sort of calculation is not so interesting (compared to QCD). What has been done is the merging of two BHs (including the gravitational radiation and the resulting anisotropic effects)
Walter
<black-hole><general-relativity><n-body-simulations>
What are the biggest problems about the numerical, finite-element GR models?
Milkman
# What are the biggest problems about the numerical, finite-element GR models?

(Asked by: username_0 on 2014-09-16)

As I know, for example the modelling of the collapse of a neutron star (to a black hole) wasn't done correctly until now.

Why? Yes, I know, the Einstein Field Equations aren't really easy to solve. But, for example, the situation is very similar in the case of the QCD, but there are already fruitful results existing ( <http://physicsworld.com/cws/article/news/2008/nov/21/proton-and-neutron-masses-calculated-from-first-principles> ).

Is there any theoretical obstacle in the way? Or we simply didn't have enough fast computers/physicist/programmer manyear until now?

**Tags:** black-hole, general-relativity, n-body-simulations
> **Comments:**
> **username_1**: Can you give more details about the model you have found?  
> **username_2**: Perhaps, this sort of calculation is not so interesting (compared to QCD). What has been done is the merging of two BHs (including the gravitational radiation and the resulting anisotropic effects)  

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## 1 answers

### Answer by username_3 on 2016-04-28. Score: 1

If you can provide examples of numerical methods in GR you've seen/heard of that would help focus the question.

From the article you linked to: "The technique keeps track of a vast number of quarks and gluons by describing the space and time inside a proton with a set of points that make up a 4D lattice". This almost gets to the main issue with Numerical Relativity. There is no natural computational grid on which to simulate space-time. The whole game with GR is that gravity is space-time so first you have to simulate the space-time and then you have to simulate the objects (neutron stars, black holes, gravitational waves) on top.

As the links below go into, its very difficult to create a consistent computational grid since the physical space-time your trying to simulate for a black hole has "funny" things in it like singularities, or an event horizon pas which we can't really know what's going on.

I think this article: <http://astronomy.com/magazine/2016/02/putting-einstein-to-the-test?page=1>

does a good job of summing up the field, and its quite accessible.

For something more rigorous please see: <http://arxiv.org/pdf/1010.5260v2.pdf>
That paper gets into some of the math behind the article linked to above.


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