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When can globular clusters be considered collisionless?

  1. May 26, 2015 #1
    Hi all.

    I'd like to use a software package, that has been designed for collisionless dynamics, to investigate general globular clusters. As they are highly collisional, at least in their inner parts, this perhaps makes no sense.

    However, it may be meaningful for some time- or length-scales or to obtain their global properties, such as luminosity, velocity dispersion, etc.

    Do you have any idea?

    If that is anyway illegal, what software do you suggest that can be run on a single high-performance PC?
    ( I mean without having PC clusters, GPUs, GRAPE, supercomputers, etc.)

    Thanks a lot.
  2. jcsd
  3. May 26, 2015 #2


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    Staff: Mentor

    Are you asking us to suggest a software package to you?
  4. May 27, 2015 #3
    The code I used for some globular cluster (NGC 2419) was NMODY, which had been written for COLLISIONLESS stellar systems. For NGC 2419 it is legal, cause its relaxation time is very long (longer than the Hubble time). (K.Derakhshani, ApJ, 783, 48, 2014)

    Now, I want to use it (or some other collisionless code) for the total range of Galactic globular clusters.

    Under what conditions (if any) will this be legal?

    If none, what other software do you suggest to me that can be run on a single PC?

  5. May 27, 2015 #4


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    Staff: Mentor

    Your word use here is slightly confusing. 'Legal' usually means that something isn't against the law or rules. Are you asking under what conditions this software would be appropriate to use and give good results?
  6. May 27, 2015 #5
    Thank you for your comment.
    In a wider prospect "legal" means "concordance with the rules of the game". In scientific workss it stands for "not violating the discipline, some scientific law, etc.". For example, if something violates the LAW of conservation of linear momentum, it will be "ILLEGAL".

    Anyway, you got it. Do you have any answer to my question?
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