diff --git a/ch03/note05.md b/ch03/note05.md index 92ae6ee2..a5d30724 100644 --- a/ch03/note05.md +++ b/ch03/note05.md @@ -13,17 +13,17 @@ **For operators** -$${\hat{A}\psi_i(x,y,z) = A_n\psi_i(x,y,z)}$$ +$${\hat{A}\psi_n = A_n\psi_n}$$ -- This is an eigenvalue problem solution of which yields $n = 1,2,3,...$ number of eigenfunctions $\psi_i$ and the eigenvalues $E_i$. Depending on boundary conditions there could be finite or infinite number of solutions. +- This is an eigenvalue problem solution of which yields $n = 1,2,3,...$ number of eigenfunctions $\psi_n$ and the eigenvalues $E_i$. Depending on boundary conditions there could be finite or infinite number of solutions. -:::{note} **Example: find eigenvalues and eigenfunctions of momentum operator** +:::{admonition} **Example: find eigenvalues and eigenfunctions of momentum operator** :class: note What are the eigenfunctions and eigenvalues of an operator $\hat{A} = d/dx$ ::: -:::{note} **Solution** +:::{{admonition} **Solution** :class: dropdown Finding eigenfunctions/eigenvalue of differnetial operators analytically involves solving differnetial equations @@ -40,7 +40,7 @@ $${f_k = e^ce^{kx} = c'e^{kx}}$$ $$Av = \lambda v$$ -:::{note} **Example: finding eigenvalues of a matrix** +:::{admonition} **Example: finding eigenvalues of a matrix** :class: note $$\begin{pmatrix} @@ -55,9 +55,9 @@ v_2 \end{pmatrix}$$ ::: -::::{admonition} +:::{admonition} -```python +:::python import numpy as np # Define the matrix @@ -68,36 +68,51 @@ eigenvalues, eigenvectors = np.linalg.eig(matrix) # Display the eigenvalues and eigenvectors eigenvalues, eigenvectors -``` -:::: +::: +::: +### Eigenfunctions of Hermitian operators form complete basis set +The three crucial consequences of Hermitian property of operators +::::{grid} +:gutter: 2 -### Eigenfunctions of Hermitian operators form complete basis set +:::{grid-item-card} Integral Notation -The three crucial consequences of Hermitian property of operators +$$\int \phi^* \hat{H}\psi dx = \int \psi (\hat{H}\phi)^*dx$$ + +::: + +:::{grid-item-card} Dirac Notation $$\langle \phi \mid \hat{H} \mid \psi \rangle = \langle \psi \mid \hat{H}\mid \phi \rangle^*$$ -- Eigenvalues are real: +::: + + +:::: + + + +- **Eigenvalues are real**: $$\hat{H} \mid \psi_n \rangle=E_n \mid \psi_n \rangle$$ $$E_n=E^*_n$$ -- Eigenfunctions are orthogonal (and can also be normalized) +- **Eigenfunctions are orthogonal** $$\langle \psi_n \mid \psi_m\rangle=\delta_{nm}$$ -- Eigenfunctions form a complete basis set! +- **Eigenfunctions form a complete basis set!** $$\mid f\rangle = \sum_i c_i \mid \psi_i \rangle$$ -- The last two properties imply that eigenfunctions of Hermitian opeartors play the same role for functions as the unit vectors for vectors. That is a function can be expressed in terms of the eigenfunctions of an opearators which can act on the function. +- The last two properties imply that eigenfunctions of Hermitian opeartors play the same role for functions as the unit vectors for vectors. Thus a wavefunction can be expressed in terms of the eigenfunctions of an opearators which can act on the function. ### Wave function as a linear superoposition of eigenfunctions