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Quantum mechanics describes the microscopic properties of nature in a regime where classical mechanics no longer applies. It explains phenomena such as the wave-particle duality, quantization of energy, and the uncertainty principle and is generally used in single-body systems. Use the quantum-field-theory tag for the theory of many-body quantum-mechanical systems.

1 vote
2 answers
231 views

Diagonalization of this Hamiltonian: How do I transform the differential operators?

In order to find the eigenstates of this Hamilatonian $$ H = \sum_{j=1}^3 \left( - \frac{\hbar^2}{2m} \frac{\partial^2}{\partial x_j^2}\right) + \frac{1}{2} m \omega^2 \left( (x_1 - x_2)^2 + (x_1 - x …
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1 vote
2 answers
355 views

Mnemonic for creation and anhiliation operators [closed]

I am not sure if this is question is withing the scope of this page. I have an exam in quantum mechanics in a few weeks and I always confuse anhilation and creation operator. $$ a^\dagger |n\rangle = …
iblue's user avatar
  • 632
1 vote
1 answer
734 views

Eigenvalues of the Spin Operator on a two-spin-system

I am not sure if I understand spin operators correctly. Given a two spin system in state $|++\rangle$ and an operator $S = S^{(1)} + S^{(2)}$ Then I have $$ S_z |++\rangle = (S^{(1)}_z + S^{(2)}_z) …
iblue's user avatar
  • 632
4 votes
3 answers
10k views

Commutator of $L^2$ and $X^2$, $P^2$

In our quantum mechanics script, it states that $[L^2, X^2] = 0$ and $[L^2, P^2] = 0$, therefore for the following Hamiltonan $$H = \frac{P^2}{2m} + V(X^2)$$ it is that $[H, L^2] = 0$ therefore $H$ …
iblue's user avatar
  • 632
5 votes
2 answers
8k views

Second-order energies of a quartic pertubation of a harmonic oscillator [closed]

A homework exercise was to calculate the second-order perturbation of a quantum anharmonic oscillator with the potential $$ V(x) = \frac{1}{2}x^2 + \lambda x^4. $$ We set $\hbar = 1$, $m=1$, etc. Usin …
iblue's user avatar
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