- #1
SataSata
- 39
- 2
I am trying to derive the energy spectrum of a 1D chain of identical quantum oscillators from its Hamiltonian by Fourier transforming the position and momentum operator.
I came across this: https://en.wikipedia.org/wiki/Phonon#Quantum_treatment
However, I am unsure of the mathematics. Specifically, ## \sum x_l x_{l+m} ## onwards.
I am unsure of how ## \sum x_l x_{l+m} ## and ## \sum p_l^2 ## is derived from the two Fourier transformed coordinates and how the potential energy term is expressed.
Can anybody explain or provide another source that is more clear in the math?
I came across this: https://en.wikipedia.org/wiki/Phonon#Quantum_treatment
However, I am unsure of the mathematics. Specifically, ## \sum x_l x_{l+m} ## onwards.
I am unsure of how ## \sum x_l x_{l+m} ## and ## \sum p_l^2 ## is derived from the two Fourier transformed coordinates and how the potential energy term is expressed.
Can anybody explain or provide another source that is more clear in the math?