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Simulating globular clusters over blackholes with Fortran

  1. May 31, 2008 #1
    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 blackhole 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 blackholes. I am in the physics department and so have access to the appropriate computers to run such simulations.
  2. jcsd
  3. May 31, 2008 #2
    I'm not an astronomer - can you first explain why simulating a globular star cluster interacting with a supermassive blackhole 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?
  4. May 31, 2008 #3

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    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.
  5. May 31, 2008 #4
    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.
  6. May 31, 2008 #5
    from my experience, formulate the system of differnetial equation isnt 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.
  7. May 31, 2008 #6


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    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" [Broken].

    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.
    Last edited by a moderator: May 3, 2017
  8. May 31, 2008 #7

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    Your replies ended up in the qyote.

    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.

    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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