Non-Fundamental Bosons: Explained

[michael879]

I don't really understand what it means to call a non-fundamental object a boson. For example, the helium atom. Its made of fermions, so wouldn't that prevent it from acting like a boson? If you can't have two protons, neutrons, or electrons occupy the same state, how could you have two helium atoms occupying the same state? If they can't occupy the same state, how can they be called bosons?

 

[Cthugha]

Composite bosons do usually just behave like bosons, if their inner structure does not matter (large distances, low densities, etc.).

When this condition is met, composite bosons show expected bosonic behaviour (bunching, following BE-Distribution,...)

See for example:

Comparison of the Hanbury Brown?Twiss effect for bosons and fermions
Nature 445, 402-405 (25 January 2007)

This paper shows the different behaviour of 3He and 4He due to their fermionic/bosonic nature.