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Physlib.QuantumMechanics.OneDimension.HarmonicOscillator.Basic

1d Harmonic Oscillator

The quantum harmonic oscillator in 1d. This file contains - the definition of the Schrodinger operator - the definition of eigenfunctions and eigenvalues of the Schrodinger operator in terms of Hermite polynomials - proof that eigenfunctions and eigenvalues are indeed eigenfunctions and eigenvalues.

TODO

Some preliminary results about Complex.ofReal .

To be moved.

The 1d Harmonic Oscillator

The characteristic length

23 declarations

theorem

The derivative of the inclusion RC\mathbb{R} \to \mathbb{C} is 11

Let f:RCf: \mathbb{R} \to \mathbb{C} be the function that maps a real number to its complex representation (i.e., f(x)=x+0if(x) = x + 0i). At any point xRx \in \mathbb{R}, the derivative of ff exists and is equal to 11.

theorem

The derivative of the inclusion RC\mathbb{R} \to \mathbb{C} is 11

For any real number xx, the derivative of the natural inclusion map f:RCf: \mathbb{R} \to \mathbb{C} (defined by f(x)=x+0if(x) = x + 0i) is equal to 11.

theorem

The inclusion RC\mathbb{R} \to \mathbb{C} is differentiable at xx

The inclusion map f:RCf: \mathbb{R} \to \mathbb{C}, which maps a real number xx to its complex representation x+0ix + 0i, is differentiable at any point xRx \in \mathbb{R}.

theorem

0<mω20 < \frac{m \omega}{2 \hbar}

For a one-dimensional quantum harmonic oscillator with mass mm and angular frequency ω\omega, the ratio mω2\frac{m \omega}{2 \hbar} is strictly positive, where \hbar is the reduced Planck's constant.

theorem

mω>0\frac{m \omega}{\hbar} > 0

For a one-dimensional quantum harmonic oscillator with mass mm and angular frequency ω\omega, the expression mω\frac{m \omega}{\hbar} is strictly positive, where \hbar is the reduced Planck's constant.

theorem

The mass mm of the harmonic oscillator is non-zero (m0m \neq 0)

For a one-dimensional quantum harmonic oscillator, the mass mm is non-zero (m0m \neq 0).

definition

Characteristic length ξ=mω\xi = \sqrt{\frac{\hbar}{m \omega}}

The characteristic length ξ\xi of a one-dimensional quantum harmonic oscillator with mass mm and angular frequency ω\omega is defined as ξ=mω\xi = \sqrt{\frac{\hbar}{m \omega}}, where \hbar is the reduced Planck constant.

theorem

ξ0\xi \ge 0

The characteristic length ξ\xi of a one-dimensional quantum harmonic oscillator is non-negative, satisfying 0ξ0 \le \xi.

theorem

ξ>0\xi > 0

The characteristic length ξ\xi of a one-dimensional quantum harmonic oscillator, defined as ξ=mω\xi = \sqrt{\frac{\hbar}{m \omega}} (where \hbar is the reduced Planck constant, mm is the mass, and ω\omega is the angular frequency), is strictly positive, i.e., 0<ξ0 < \xi.

theorem

Characteristic length ξ0\xi \neq 0 for the 1D Harmonic Oscillator

The characteristic length ξ\xi of a one-dimensional quantum harmonic oscillator, defined as ξ=mω\xi = \sqrt{\frac{\hbar}{m \omega}} (where \hbar is the reduced Planck constant, mm is the mass, and ω\omega is the angular frequency), is non-zero, i.e., ξ0\xi \neq 0.

theorem

ξ2=mω\xi^2 = \frac{\hbar}{m \omega} for the 1D Harmonic Oscillator

For a one-dimensional quantum harmonic oscillator with mass mm, angular frequency ω\omega, and reduced Planck constant \hbar, the square of the characteristic length ξ\xi is given by ξ2=mω.\xi^2 = \frac{\hbar}{m \omega}.

theorem

ξ=ξ|\xi| = \xi for the 1D Harmonic Oscillator

For a one-dimensional quantum harmonic oscillator, the absolute value of the characteristic length ξ\xi is equal to ξ\xi, i.e., ξ=ξ|\xi| = \xi. Here, ξ\xi is defined as mω\sqrt{\frac{\hbar}{m \omega}}, where mm is the mass, ω\omega is the angular frequency, and \hbar is the reduced Planck constant.

theorem

1ξ=mω\frac{1}{\xi} = \sqrt{\frac{m \omega}{\hbar}} for the 1D Harmonic Oscillator

For a one-dimensional quantum harmonic oscillator with mass mm, angular frequency ω\omega, and reduced Planck constant \hbar, the reciprocal of the characteristic length ξ\xi is given by 1ξ=mω.\frac{1}{\xi} = \sqrt{\frac{m \omega}{\hbar}}.

theorem

ξ1=mω\xi^{-1} = \sqrt{\frac{m \omega}{\hbar}} for the 1D Harmonic Oscillator

For a one-dimensional quantum harmonic oscillator with mass mm, angular frequency ω\omega, and reduced Planck constant \hbar, the multiplicative inverse of the characteristic length ξ\xi is given by ξ1=mω.\xi^{-1} = \sqrt{\frac{m \omega}{\hbar}}.

theorem

(1ξ)2=mω(\frac{1}{\xi})^2 = \frac{m \omega}{\hbar} for the 1D Harmonic Oscillator

For a one-dimensional quantum harmonic oscillator with mass mm, angular frequency ω\omega, and reduced Planck constant \hbar, the square of the reciprocal of the characteristic length ξ\xi is given by (1ξ)2=mω.\left(\frac{1}{\xi}\right)^2 = \frac{m \omega}{\hbar}.

definition

Momentum operator notation PopP^{op}

The notation PopP^{op} represents the momentum operator p^\hat{p} in the context of the one-dimensional quantum harmonic oscillator.

definition

Position operator XopX^{\text{op}}

The notation XopX^{\text{op}} represents the position operator within the context of a one-dimensional quantum harmonic oscillator. It is defined as a synonym for the `positionOperator`.

definition

Schrödinger operator of the 1D harmonic oscillator

The Schrödinger operator for a one-dimensional harmonic oscillator with mass mm and angular frequency ω\omega is an operator that maps a wavefunction ψ:RC\psi: \mathbb{R} \to \mathbb{C} to the function defined by: (H^ψ)(x)=22md2ψdx2(x)+12mω2x2ψ(x)( \hat{H} \psi )(x) = -\frac{\hbar^2}{2m} \frac{d^2\psi}{dx^2}(x) + \frac{1}{2} m \omega^2 x^2 \psi(x) where \hbar is the reduced Planck constant and d2ψdx2\frac{d^2\psi}{dx^2} is the second derivative of ψ\psi.

theorem

Explicit expression for the Schrödinger operator H^\hat{H} of the 1D harmonic oscillator

For a wavefunction ψ:RC\psi: \mathbb{R} \to \mathbb{C}, the Schrödinger operator H^\hat{H} for a one-dimensional harmonic oscillator with mass mm and angular frequency ω\omega is given by the formula: H^ψ=22md2ψdx2+12mω2x2ψ\hat{H} \psi = -\frac{\hbar^2}{2m} \frac{d^2 \psi}{dx^2} + \frac{1}{2} m \omega^2 x^2 \psi where \hbar is the reduced Planck constant and d2ψdx2\frac{d^2 \psi}{dx^2} denotes the second derivative of ψ\psi with respect to the spatial coordinate.

theorem

Expression of the Schrödinger operator H^\hat{H} in terms of the characteristic length ξ\xi

For a wavefunction ψ:RC\psi: \mathbb{R} \to \mathbb{C}, the Schrödinger operator H^\hat{H} of a one-dimensional quantum harmonic oscillator with mass mm and characteristic length ξ\xi is given by: (H^ψ)(x)=22m(d2ψdx2(x)+x2ξ4ψ(x))(\hat{H} \psi)(x) = \frac{\hbar^2}{2m} \left( -\frac{d^2\psi}{dx^2}(x) + \frac{x^2}{\xi^4} \psi(x) \right) where \hbar is the reduced Planck constant, d2ψdx2\frac{d^2\psi}{dx^2} denotes the second derivative of ψ\psi, and ξ=mω\xi = \sqrt{\frac{\hbar}{m \omega}} is the characteristic length related to the angular frequency ω\omega.

theorem

The Schrödinger operator commutes with the parity operator (H^P^=P^H^\hat{H}\hat{P} = \hat{P}\hat{H})

For any wavefunction ψ:RC\psi: \mathbb{R} \to \mathbb{C}, the Schrödinger operator H^\hat{H} for a one-dimensional harmonic oscillator commutes with the parity operator P^\hat{P}. That is, H^(P^ψ)=P^(H^ψ)\hat{H}(\hat{P} \psi) = \hat{P}(\hat{H} \psi) where the parity operator is defined as (P^ψ)(x)=ψ(x)(\hat{P}\psi)(x) = \psi(-x) and the Schrödinger operator is defined as (H^ψ)(x)=22md2ψdx2(x)+12mω2x2ψ(x)(\hat{H} \psi)(x) = -\frac{\hbar^2}{2m} \frac{d^2\psi}{dx^2}(x) + \frac{1}{2} m \omega^2 x^2 \psi(x) with mm being the mass, ω\omega the angular frequency, and \hbar the reduced Planck constant.

theorem

Additivity of the Schrödinger operator: H^(ψ+ϕ)=H^ψ+H^ϕ\hat{H}(\psi + \phi) = \hat{H}\psi + \hat{H}\phi

Let ψ,ϕ:RC\psi, \phi : \mathbb{R} \to \mathbb{C} be two functions representing wavefunctions. If ψ\psi and ϕ\phi are twice differentiable, then the Schrödinger operator H^\hat{H} for a one-dimensional harmonic oscillator satisfies: H^(ψ+ϕ)=H^ψ+H^ϕ\hat{H}(\psi + \phi) = \hat{H}\psi + \hat{H}\phi where the Schrödinger operator is defined as (H^ψ)(x)=22md2ψdx2(x)+12mω2x2ψ(x)(\hat{H} \psi)(x) = -\frac{\hbar^2}{2m} \frac{d^2\psi}{dx^2}(x) + \frac{1}{2} m \omega^2 x^2 \psi(x).

theorem

Homogeneity of the Schrödinger operator: H^(cψ)=cH^ψ\hat{H}(c\psi) = c\hat{H}\psi

For any complex scalar cCc \in \mathbb{C} and any wavefunction ψ:RC\psi: \mathbb{R} \to \mathbb{C}, if ψ\psi is twice differentiable, the Schrödinger operator H^\hat{H} for a one-dimensional harmonic oscillator satisfies the homogeneity property: H^(cψ)=c(H^ψ)\hat{H}(c \psi) = c (\hat{H} \psi) where the Schrödinger operator is defined as (H^ψ)(x)=22md2ψdx2(x)+12mω2x2ψ(x)(\hat{H} \psi)(x) = -\frac{\hbar^2}{2m} \frac{d^2\psi}{dx^2}(x) + \frac{1}{2} m \omega^2 x^2 \psi(x) with mm being the mass, ω\omega the angular frequency, and \hbar the reduced Planck constant.