A Help with proof of eq. 2.64 of Intro. to Quantum Mechanics

SherLOCKed
Messages
13
Reaction score
1
I am self studying the Book- Introduction to Quantum Mechanics , 2e. Griffith. Page 47.
While the book has given a proof for eq. 2.64 but its not very ellaborate
Integral(infinity,-infinity) [f*(a±g(x)).dx] = Integral(infinity,-infinity) [(a±f)* g(x).dx] . It would be great help if somebody could provide me a more step by step proof of the same.
Where a+ and a- are roots of Hamiltonian of harmonic oscillator problem.
 
Physics news on Phys.org
Are a+ and a- real? If so it would be justified.
 
The operator

$${d \over dx}$$ picks up a minus sign under hermitian conjugation when the hilbert space is that of functions that vanish fast enough at infinity. The reason why that's true is because:

$$\int f {d g \over dx} = 0 - \int g {df \over dx} dx$$

This implies that when you take the hermitian conjugate of the $\hat{a}_+$ operator, just replace ${d \over dx}$ by $-{d \over dx}$ which gives the $\hat{a}_-$ operator
 
  • Like
Likes BvU
SherLOCKed said:
Where a+ and a- are roots of Hamiltonian of harmonic oscillator
Be careful there: they are not! There is a constant ##\hbar\omega## difference !
 
Insights auto threads is broken atm, so I'm manually creating these for new Insight articles. Towards the end of the first lecture for the Qiskit Global Summer School 2025, Foundations of Quantum Mechanics, Olivia Lanes (Global Lead, Content and Education IBM) stated... Source: https://www.physicsforums.com/insights/quantum-entanglement-is-a-kinematic-fact-not-a-dynamical-effect/ by @RUTA
If we release an electron around a positively charged sphere, the initial state of electron is a linear combination of Hydrogen-like states. According to quantum mechanics, evolution of time would not change this initial state because the potential is time independent. However, classically we expect the electron to collide with the sphere. So, it seems that the quantum and classics predict different behaviours!
Back
Top