Teoria perturbativa

Question 1

What is the perturbation in the theory of perturbations?

Answer 1

The perturbation in the theory of perturbations is λH(1), where λ is a small parameter and H(1) is the perturbation Hamiltonian.

Question 2

What is the equation used to find the corrections to the eigenfunctions of the system at the first order?

Answer 2

The equation used to find the corrections to the eigenfunctions of the system at the first order is ψ(1)n = -∑m≠n(<ψ0m|H(1)|ψ0n>)/(E0m - E0n)ψ0m.

Question 3

What is the equation used to find the corrections to the energy of the system at the first order?

Answer 3

The equation used to find the corrections to the energy of the system at the first order is E(1)n = <ψ0n|H(1)|ψ0n>.

Question 4

What is the difference between the corrections to the energy and the eigenfunctions of a system?

Answer 4

The corrections to the energy of a system can be obtained using only the eigenfunctions of the unperturbed system, while the corrections to the eigenfunctions require the knowledge of the perturbed eigenfunctions.