- #1
Alexios
- 3
- 0
Hello,
I'm struggling with the second quantization formalism. I'd like to derive the hamiltonian of a system with non-interacting particles
[tex]\hat{H}=\int dx\,a(x)^\dagger \left[\frac{\hat{P}}{2m}+V(x)\right]a(x),[/tex]
where [tex]a(x) = \hat{\Psi}(x)[/tex].
I know the second quantized representation of a single-particle operator [tex]\hat{O}[/tex] which is diagonal in the basis [tex]\{|\alpha\rangle\}[/tex]:
[tex]\hat{O}=\sum_i o_{\alpha_i} a_{\alpha_i}^\dagger a_{\alpha_i}[/tex]
My idea was, as a first step, to derive the expression of the linear momentum operator:
[tex]\hat{P}=\sum_i p_{p_i} a_{p_i}^\dagger a_{p_i} =\sum_i \int dx\, \langle x|p_i\rangle a^\dagger(x) \int dx\, \langle p_i|x\rangle a(x) ??[/tex]
The above is probably wrong (and I don't know how to proceed in order to derive an expression which is of similar form as [tex]\hat{H}[/tex])
Any help is much appreciated.
I'm struggling with the second quantization formalism. I'd like to derive the hamiltonian of a system with non-interacting particles
[tex]\hat{H}=\int dx\,a(x)^\dagger \left[\frac{\hat{P}}{2m}+V(x)\right]a(x),[/tex]
where [tex]a(x) = \hat{\Psi}(x)[/tex].
I know the second quantized representation of a single-particle operator [tex]\hat{O}[/tex] which is diagonal in the basis [tex]\{|\alpha\rangle\}[/tex]:
[tex]\hat{O}=\sum_i o_{\alpha_i} a_{\alpha_i}^\dagger a_{\alpha_i}[/tex]
My idea was, as a first step, to derive the expression of the linear momentum operator:
[tex]\hat{P}=\sum_i p_{p_i} a_{p_i}^\dagger a_{p_i} =\sum_i \int dx\, \langle x|p_i\rangle a^\dagger(x) \int dx\, \langle p_i|x\rangle a(x) ??[/tex]
The above is probably wrong (and I don't know how to proceed in order to derive an expression which is of similar form as [tex]\hat{H}[/tex])
Any help is much appreciated.