Spread fo wavefunctions - filling the universe?

[franoisbelfor]

Wavefunctions spread with time, if the particle does not interact.
Now, the universe is filled with particles that do not interact for
thousands and millions of years, for example cosmic ray protons.

This would mean most space in the universe is filled with
wavefunctions, all overlapping.

Does this give problems with the exclusion principle?
Did anybody calculate such effects?
Does this explain the expansion of the universe?


François

 

[atyy]

It doesn't give any problems with the exclusion principle (thankfully). If the particles are far away, we don't make a big mistake if we don't include them in the anti-symmetrization of the wavefunction. Shankar discusses this I think.

 

[gendou2]

the wave function for, say an electron, extends throughout all space. but, this does not mean the electron itself exists everywhere. there's a probability (specifically, the square of the wave function) that when you look, you'll find the electron at a given place. you don't know if it's at a given place or not for sure until you look. you'll never see two electrons on top of each other when you do look, though, due to the exclusion principle.