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.

 

[charng]

I can understand your confusion about non-fundamental bosons. Let me try to explain it in simpler terms. Bosons are particles that follow Bose-Einstein statistics, which means they can occupy the same quantum state at the same time. This is in contrast to fermions, which follow Fermi-Dirac statistics and cannot occupy the same quantum state simultaneously.

The helium atom is indeed made up of fermions - two protons, two neutrons, and two electrons. However, when these fermions come together to form an atom, they behave as a collective entity and can be described as a boson. This is because the overall spin of the helium atom is 0, which is characteristic of bosons. This allows multiple helium atoms to occupy the same state, as long as their overall spin remains 0.

In terms of the helium atom, this means that two helium atoms can occupy the same energy level, as long as their overall spin remains 0. This is different from fermions like electrons, where two electrons cannot occupy the same energy level.

In summary, even though the constituent particles of a non-fundamental boson may be fermions, when they come together to form a collective entity, they exhibit bosonic behavior. I hope this helps to clarify the concept of non-fundamental bosons for you.