Statistical mechanics with a negative amount of atoms

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Discussion Overview

The discussion revolves around the theoretical implications of allowing a negative number of particles (N < 0) in statistical mechanics. Participants explore the conceptual and physical ramifications of this idea, questioning its validity and potential applications in various systems.

Discussion Character

  • Exploratory
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • One participant suggests that while their professor claims N cannot be negative, they believe it should be theoretically considered, proposing that some systems might exhibit statistical behavior that could be explained by N < 0.
  • Another participant questions the physical meaning of having a negative number of particles, asking what it would mean to say "I have negative four atoms in this box."
  • There is a query about the possibility of having a positive thermodynamic temperature with N < 0, indicating a potential conflict between these concepts.
  • A participant posits that a system with N < 0 would likely be quantum in nature, regardless of whether it involves bosons or fermions.
  • Concerns are raised about the lack of physical meaning in negative particle numbers, even in quantum statistical mechanics, where fluctuations do not allow for negative particle counts.

Areas of Agreement / Disagreement

Participants express disagreement regarding the validity and implications of negative particle numbers in statistical mechanics. While some assert that it makes no physical sense, others advocate for the theoretical exploration of the concept.

Contextual Notes

Participants highlight the ambiguity surrounding the implications of negative particle numbers and the conditions under which thermodynamic temperature is defined, indicating a need for further clarification on these concepts.

Who May Find This Useful

This discussion may be of interest to those studying advanced statistical mechanics, quantum mechanics, or theoretical physics, particularly in the context of particle statistics and thermodynamics.

Catria
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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?
 
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Do you know why thermodynamic temperature must be a positive quantity?
 
Dickfore said:
Do you know why thermodynamic temperature must be a positive quantity?

Is it possible to have a thermodynamic themperature > 0 with N < 0?
 
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.
 
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.
 
Catria said:
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?

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.
 

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