Symmetrisation of wave function for fermions

In summary, the wave function for fermions must be anti-symmetric with respect to the exchange of electron positions. This also applies to the wave vector and position representations, but not both at the same time. If there is an additional degree of freedom, such as spin, the full state must be anti-symmetric. In the case of particles in continuum described by a Coulomb wave function, which depends on both wave vector and position, the system is in a singlet state so the spin-related part can be disregarded.
  • #1
djelovin
28
0
The wave function for fermions has to be anti-symmetric with respect to exchange of positions of electrons, but what if it depends on wave vector as well. Does they have to be exchanged as well, in other words, for two-electron system what is correct

Ψ(r1,k1,r2,k2) = - Ψ(r2,k1,r1,k2)

or

Ψ(r1,k1,r2,k2) = - Ψ(r2,k2,r1,k1)
 
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  • #2
The wave vector and the position are just different representations of the same Hilbert space. You can use either to represent your state but not both at the same time.

That being said, it is the overall state that should be antisymmetric under the exchange of the electrons. If you have an additional degree of freedom that the state depends on (spin comes to mind) then you need to make the full state antisymmetric. If the state in the additional degree of freedom is already antisymmetric your spatial wavefunction will be symmetric. Positronium in the spin-0 state comes to mind.
 
  • #3
Thanx for quick replay,
That somewhat clarifies my problem.
However I have particles in continuum, in the presence of some potential, that are described by Coulomb (Coulomb-like to be more precise) wave function that does depend on both, wave vector and position at the same time.
https://en.wikipedia.org/wiki/Coulomb_wave_function
The system is in singlet state, so spin related part can be taken out.
 
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1. What is the symmetrisation of a wave function for fermions?

The symmetrisation of a wave function for fermions is a process that involves rearranging the wave function in order to satisfy the Pauli exclusion principle. This principle states that no two fermions can occupy the same quantum state simultaneously, so the symmetrisation ensures that the wave function reflects this principle.

2. Why is it necessary to symmetrise the wave function for fermions?

Symmetrisation of the wave function for fermions is necessary in order to accurately describe the behavior of fermions, which are particles with half-integer spin. Without symmetrisation, the wave function would not reflect the Pauli exclusion principle and would not accurately represent the behavior of fermions.

3. How is the symmetrisation of the wave function for fermions carried out?

The symmetrisation of the wave function is carried out by applying the appropriate mathematical operations, depending on the specific system being studied. In general, the wave function is rearranged in such a way that it reflects the Pauli exclusion principle, ensuring that no two fermions occupy the same quantum state.

4. What are the implications of symmetrising the wave function for fermions?

The symmetrisation of the wave function for fermions has important implications for various physical phenomena, such as the behavior of electrons in atoms and the properties of solids. It allows for a more accurate description of the behavior of fermions and helps to explain various experimental observations.

5. Are there any exceptions to the symmetrisation of the wave function for fermions?

In certain cases, such as in superconductors, the symmetrisation of the wave function for fermions may not be necessary. This is because the wave function can be modified by other factors, such as the presence of a superconducting gap, which can override the need for symmetrisation. However, in most cases, symmetrisation is an important aspect of accurately describing the behavior of fermions.

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