Simulating globular clusters over blackholes with Fortran

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Discussion Overview

The discussion revolves around the feasibility and methodology of simulating globular star clusters interacting with supermassive black holes using Fortran. Participants explore the complexities of such simulations, including the computational requirements and the physical models involved, while also considering alternative scenarios like binary red giant star systems. The conversation touches on theoretical and practical aspects of astrophysical simulations.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant questions the interest in simulating globular clusters with supermassive black holes and asks for clarification on the goals of such a simulation.
  • There is a discussion on the feasibility of treating stars as point particles and how the number of operations scales with the number of stars in the system.
  • Some participants argue that the mass of stars does not affect the complexity of calculations, as the same equations apply regardless of mass.
  • Concerns are raised about the misconception that globular clusters contain supermassive black holes, with some evidence suggesting only intermediate mass black holes may be present.
  • Participants note that globular clusters typically contain hundreds of thousands of stars, not just thousands, and discuss the computational challenges of simulating such large systems.
  • There is mention of existing N-body simulation codes that could be utilized instead of creating new simulations from scratch.
  • One participant expresses uncertainty about the hardware requirements for such simulations and acknowledges their limited experience in computer modeling.
  • A later reply emphasizes the importance of understanding the simplifications and approximations used in astrophysical modeling and suggests consulting faculty for deeper insights.

Areas of Agreement / Disagreement

Participants express multiple competing views regarding the presence of black holes in globular clusters, the computational feasibility of simulations, and the best approaches to modeling such systems. The discussion remains unresolved on several points, particularly concerning the specifics of simulation methodologies and the implications of findings.

Contextual Notes

Limitations include the dependence on assumptions about star interactions, the scale of simulations, and the computational resources required. There is also a lack of consensus on the theoretical frameworks and models applicable to the discussion.

Who May Find This Useful

This discussion may be useful for students and researchers interested in astrophysics, computational modeling, and the dynamics of star systems, particularly those exploring simulation techniques and theoretical implications in astrophysical contexts.

Benzoate
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I suspect that the runtime simulation for a star systems containing thousands of stars , many of those stars whose mass is way beyond the solar mass to be very very long. Is it possible and cost-friendly(i.e, not expensive) to simulate a globular star system cluster over a supermassive black hole on Fortran? This is the topic I am playing around with ; I am also thinking of maybe just simulating a binary redgiant star system over a black hole . But I haven't really seen many papers on Red giant star that orbit around black holes. I am in the physics department and so have access to the appropriate computers to run such simulations.
 
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I'm not an astronomer - can you first explain why simulating a globular star cluster interacting with a supermassive black hole is interesting? Is there an idea you want to demonstrate or test?

To determine whether the calculation is feasible you first need to decided how much detail is necessary in your model. Can you treat the stars in the cluster as point particles which interact only through gravity?

If you treat the stars as point particles interacting with each other through gravity how does the number of operations required to calculate the forces on each particle scale with the number of stars in the system?
 
1) I don't see why having a heavy star takes any longer to calculate than a light star. The equations are the same, only the numbers are different.

2) Globular clusters do not have supermassive black holes in their centers. There is some evidence that some (okay, two) may have intermediate mass black holes, but this evidence is far from unambiguous.

3) Globular clusters have hundreds of thousands of stars, not thousands.

4) So far as I know, no simulation tries to calculate the dynamics of 10^5 objects by looking at all 10^10 two-body interactions. This is prohibitively expensive. They either use fewer stars, potential approximations, or a mix of the two.

5) I have a hard time with "I have access to the appropriate computers", because if you did, you would likely have mentioned them by name. (e.g. GRAPE-6) I don't think you quite understand what hardware this sort of calculation entails.
 
Vanadium 50 said:
1) I don't see why having a heavy star takes any longer to calculate than a light star. The equations are the same, only the numbers are different.

2) Globular clusters do not have supermassive black holes in their centers. There is some evidence that some (okay, two) may have intermediate mass black holes, but this evidence is far from unambiguous.

But most galaxies contained at least one supermassive black hole at there very center. galaxies contained globular clusters.

3) Globular clusters have hundreds of thousands of stars, not thousands.

You were right and I was wrong. There is nothing more to say on that issue.

4) So far as I know, no simulation tries to calculate the dynamics of 10^5 objects by looking at all 10^10 two-body interactions. This is prohibitively expensive. They either use fewer stars, potential approximations, or a mix of the two.

So how would physicists confirmed that there theory on globular clusters orienting themselves in a certain manner if whether or not there theory is correct or incorrect if they do not have the experimental tools to simulate their model of how globular clusters move?

5) I have a hard time with "I have access to the appropriate computers", because if you did, you would likely have mentioned them by name. (e.g. GRAPE-6) I don't think you quite understand what hardware this sort of calculation entails.

You are correct. I really do not know much about computer modeling. I'm only a sophomore in physics trying to find an interesting simulation of a star system , that is within my reach.
 
from my experience, formulate the system of differnetial equation isn't the hardest part. Perhaps you can start on that. After that you can find some numerical method to solve that system. After all that should just become a giant system of differential equations.

After you formulate it, try to explain why it might become difficult.
 
What is the purpose of this project? If you are interested in the physics then I would advise against re-inventing the wheel. There are many many freely available computer codes to run N-Body simulations. I use http://www.mpa-garching.mpg.de/galform/gadget/index.shtml" .

If you are interested in the process of the simulation, then writing your own code is an interesting project. It just depends on what your focus is.
 
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Benzoate said:
But most galaxies contained at least one supermassive black hole at there very center. galaxies contained globular clusters.

This is not a reason to conclude supermassive black holes are in the center of globular clusters. Kansas City is at the center of the US. The US contains other states. Therefore Kansas City is in the center of Massachusetts?

Supermassive black holes weigh as much as or more than an entire globular cluster.

Benzoate said:
So how would physicists confirmed that there theory on globular clusters orienting themselves in a certain manner if whether or not there theory is correct or incorrect if they do not have the experimental tools to simulate their model of how globular clusters move?

An excellent question, and one you should ask the faculty at your university. They can explain in great detail all the simplifications and approximations they use.
 

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