What is the Optimal Size for a Cosmological N-Body Simulation Box?

In summary, the conversation discusses the identification of the size of a simulation box in cosmological n-body simulations using physical scales in the universe. Two possible methods are mentioned: equating the density of particles in the simulation box with the actual density of galaxies, and finding the size of a spherical region at z=0 with density fluctuations of unity. A paper on the topic is also referenced.
  • #1
cosmoboy
65
0
Hi,
Could some body please explain me how to identfy the size of simulation box in cosmological n-body simulation with the physical scales in the universe. For example if I am using 128 grid points along one direction in a Particle Mesh code and total number of particles are 128*128*1228. Now there are two options, first is; we equate the density of particles in simulation box and compare it with the actual density of galaxies in the universe (for simulating galaxy clustering)
and second, we find the size of a spherical region at z=0, in which density fluctuatios are of the order of unity and identify it with
8 Mpc (Using COBE normalization, CDM spectrum).
Let me know if anyone has the answer
 
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  • #2
I cannot answer your question, but I a short time ago I had also some questions related N-body simulations (https://www.physicsforums.com/showthread.php?t=43890). I did search some information about the subject and I found this paper:

Cosmological N-Body simulation: Techniques, Scope and Status
http://arxiv.org/abs/astro-ph/0411043

May be it helps (although I had no time to read it till now and I do not know whether there is an answer to your question there).
 
Last edited:
  • #3
dear hellfire ,
thanks
 

1. What is an N-body simulation?

An N-body simulation is a computational method used to model the motion and interactions of a system of particles, such as stars or planets. It takes into account the gravitational forces between these particles and predicts their future positions and velocities.

2. What are the applications of N-body simulations?

N-body simulations are used in a variety of scientific fields, including astrophysics, cosmology, and molecular dynamics. They are particularly useful for studying the behavior of large-scale structures, such as galaxies and galaxy clusters, or for understanding the dynamics of molecular systems.

3. How accurate are N-body simulations?

The accuracy of an N-body simulation depends on the number of particles included in the model and the precision of the calculations used. Generally, the more particles included and the more detailed the calculations, the more accurate the simulation will be. However, even with advanced computing power, it is impossible to create a perfectly accurate simulation due to the chaotic nature of many-body systems.

4. How do N-body simulations handle collisions between particles?

In most cases, N-body simulations assume that particles are point masses and do not account for collisions between particles. However, some simulations do include collisional effects, such as in molecular dynamics simulations where the interactions between atoms and molecules are crucial to the system's behavior.

5. What are the limitations of N-body simulations?

N-body simulations are limited by the computing power available and the complexity of the system being modeled. As the number of particles increases, the computational resources required also increase, making it difficult to simulate very large systems. Additionally, N-body simulations cannot account for all physical processes, such as the effects of gas or radiation, and must make simplifying assumptions to be feasible.

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