Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Statistical mechanics with a negative amount of atoms

  1. Nov 10, 2012 #1
    My advanced statistical mechanics prof told me that it wouldn't make any physical sense to allow N (the number of particles in a system) to be negative. But, somehow, I think that this possibility should be theoretically left open; perhaps there are some systems whose statistical behavior would be best explained if we allowed N < 0.

    My question is: what would happen if we wanted to solve stat-mech problems of systems with negative quantities of particles?
  2. jcsd
  3. Nov 10, 2012 #2
    Do you know why thermodynamic temperature must be a positive quantity?
  4. Nov 10, 2012 #3
    Is it possible to have a thermodynamic themperature > 0 with N < 0?
  5. Nov 10, 2012 #4

    Vanadium 50

    User Avatar
    Staff Emeritus
    Science Advisor
    Education Advisor
    2015 Award

    Your professor is right. What does it even mean to say "I have negative four atoms in this box"? Sure, you can always plug numbers into equations, but that doesn't mean what comes out makes any sense.
  6. Nov 27, 2012 #5
    Come to think of it, a system whose statistical behavior is that of N < 0 would be quantum in nature, regardless of whether the system contains bosons or fermions.
  7. Nov 28, 2012 #6


    User Avatar
    Homework Helper

    Which systems' statistical behavior do you think would be best explained if we allowed N < 0? Do you have any examples in mind?

    I doubt there's any physical meaning to having a negative number of particles, even in quantum statistical mechanics. Even in ensembles in which you allow particle fluctuations, they don't have fluctuations to less than zero particles in the system.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?

Similar Discussions: Statistical mechanics with a negative amount of atoms