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Physlib.QuantumMechanics.OneDimension.HarmonicOscillator.Eigenfunction

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definition

nn-th eigenfunction of the harmonic oscillator

#eigenfunction

The nn-th eigenfunction of the one-dimensional harmonic oscillator, denoted as ψn:RC\psi_n: \mathbb{R} \to \mathbb{C}, is defined for a given quantum number nNn \in \mathbb{N} and characteristic length scale ξ\xi as: ψn(x)=12nn!πξHn(xξ)ex22ξ2\psi_n(x) = \frac{1}{\sqrt{2^n n! \sqrt{\pi} \xi}} H_n\left(\frac{x}{\xi}\right) e^{-\frac{x^2}{2\xi^2}} where HnH_n is the nn-th physicist's Hermite polynomial (`physHermite`). The resulting value is treated as a complex number.

theorem

Explicit Formula for the Harmonic Oscillator Eigenfunction ψn(x)\psi_n(x)

#eigenfunction_eq

For any natural number nn, the nn-th eigenfunction ψn(x)\psi_n(x) of the one-dimensional harmonic oscillator is given by the formula: ψn(x)=12nn!1πξHn(xξ)ex22ξ2\psi_n(x) = \frac{1}{\sqrt{2^n n!}} \frac{1}{\sqrt{\sqrt{\pi} \xi}} H_n\left(\frac{x}{\xi}\right) e^{-\frac{x^2}{2\xi^2}} where ξ\xi is the characteristic length scale and HnH_n is the nn-th physicist's Hermite polynomial.

theorem

ψ0(x)=1πξexp(x22ξ2)\psi_0(x) = \frac{1}{\sqrt{\sqrt{\pi} \xi}} \exp\left(-\frac{x^2}{2\xi^2}\right)

#eigenfunction_zero

The 0-th eigenfunction of the one-dimensional harmonic oscillator, denoted as ψ0:RC\psi_0: \mathbb{R} \to \mathbb{C}, is given by the expression: ψ0(x)=1πξexp(x22ξ2)\psi_0(x) = \frac{1}{\sqrt{\sqrt{\pi} \xi}} \exp\left(-\frac{x^2}{2\xi^2}\right) where ξ\xi is the characteristic length scale and xx is the position.

theorem

The nn-th harmonic oscillator eigenfunction ψn\psi_n in terms of the ground state ψ0\psi_0 and Hermite polynomials

#eigenfunction_eq_mul_eigenfunction_zero

For any natural number nNn \in \mathbb{N}, the nn-th eigenfunction ψn(x)\psi_n(x) of the one-dimensional harmonic oscillator can be expressed in terms of the ground state eigenfunction ψ0(x)\psi_0(x) as: ψn(x)=12nn!Hn(xξ)ψ0(x)\psi_n(x) = \frac{1}{\sqrt{2^n n!}} H_n\left(\frac{x}{\xi}\right) \psi_0(x) where HnH_n is the nn-th physicist's Hermite polynomial and ξ\xi is the characteristic length scale.

theorem

The nn-th Harmonic Oscillator Eigenfunction ψn\psi_n is Integrable

#eigenfunction_integrable

For any natural number nNn \in \mathbb{N}, the nn-th eigenfunction of the one-dimensional harmonic oscillator, denoted as ψn(x)\psi_n(x), is integrable. That is, the integral of the absolute value of the eigenfunction over the entire real line is finite: ψn(x)dx<\int_{-\infty}^{\infty} |\psi_n(x)| \, dx < \infty where ψn(x)\psi_n(x) is defined in terms of the nn-th physicist's Hermite polynomial HnH_n and the characteristic length scale ξ\xi as: ψn(x)=12nn!πξHn(xξ)ex22ξ2\psi_n(x) = \frac{1}{\sqrt{2^n n! \sqrt{\pi} \xi}} H_n\left(\frac{x}{\xi}\right) e^{-\frac{x^2}{2\xi^2}}

theorem

The Harmonic Oscillator Eigenfunction is Real: ψn(x)=ψn(x)\overline{\psi_n(x)} = \psi_n(x)

#eigenfunction_conj

For any natural number nNn \in \mathbb{N} and any real number xRx \in \mathbb{R}, the nn-th eigenfunction of the one-dimensional harmonic oscillator ψn(x)\psi_n(x) is real-valued. Specifically, its complex conjugate (denoted by the overline) is equal to itself: ψn(x)=ψn(x)\overline{\psi_n(x)} = \psi_n(x) This holds because the explicit definition of ψn(x)\psi_n(x) involves only real-valued components (Hermite polynomials, exponentials, and normalization constants) cast into the complex field.

theorem

Pointwise Norm of the Harmonic Oscillator Eigenfunction ψn(x)\|\psi_n(x)\|

#eigenfunction_point_norm

For any natural number nNn \in \mathbb{N} and any real number xRx \in \mathbb{R}, the norm of the nn-th eigenfunction ψn(x)\psi_n(x) of the one-dimensional harmonic oscillator is given by: ψn(x)=(12nn!1πξ)Hn(xξ)ex22ξ2\|\psi_n(x)\| = \left( \frac{1}{\sqrt{2^n n!}} \frac{1}{\sqrt{\sqrt{\pi} \xi}} \right) \left| H_n\left(\frac{x}{\xi}\right) \right| e^{-\frac{x^2}{2\xi^2}} where ξ\xi is the characteristic length scale and HnH_n is the nn-th physicist's Hermite polynomial.

theorem

Squared Norm of the Harmonic Oscillator Eigenfunction ψn(x)2\|\psi_n(x)\|^2

#eigenfunction_point_norm_sq

For any natural number nNn \in \mathbb{N} and any real number xRx \in \mathbb{R}, the squared norm of the nn-th eigenfunction ψn(x)\psi_n(x) of the one-dimensional harmonic oscillator is given by: ψn(x)2=(12nn!1πξ)2Hn(xξ)2ex2ξ2\|\psi_n(x)\|^2 = \left( \frac{1}{\sqrt{2^n n!}} \frac{1}{\sqrt{\sqrt{\pi} \xi}} \right)^2 H_n\left(\frac{x}{\xi}\right)^2 e^{-\frac{x^2}{\xi^2}} where ξ\xi is the characteristic length scale and HnH_n is the nn-th physicist's Hermite polynomial.

theorem

The harmonic oscillator eigenfunctions ψn\psi_n are square-integrable

#eigenfunction_square_integrable

For any natural number nNn \in \mathbb{N}, the nn-th eigenfunction ψn\psi_n of the one-dimensional harmonic oscillator is square-integrable, meaning the function xψn(x)2x \mapsto \|\psi_n(x)\|^2 is integrable over R\mathbb{R}. The eigenfunction ψn\psi_n is defined as: ψn(x)=12nn!πξHn(xξ)ex22ξ2\psi_n(x) = \frac{1}{\sqrt{2^n n! \sqrt{\pi} \xi}} H_n\left(\frac{x}{\xi}\right) e^{-\frac{x^2}{2\xi^2}} where ξ\xi is the characteristic length scale and HnH_n is the nn-th physicist's Hermite polynomial.

theorem

The harmonic oscillator eigenfunctions ψn\psi_n are almost everywhere strongly measurable

#eigenfunction_aeStronglyMeasurable

For any natural number nNn \in \mathbb{N}, the nn-th eigenfunction of the one-dimensional harmonic oscillator, ψn:RC\psi_n: \mathbb{R} \to \mathbb{C}, is almost everywhere strongly measurable. The eigenfunction is defined as: ψn(x)=12nn!πξHn(xξ)ex22ξ2\psi_n(x) = \frac{1}{\sqrt{2^n n! \sqrt{\pi} \xi}} H_n\left(\frac{x}{\xi}\right) e^{-\frac{x^2}{2\xi^2}} where ξ\xi is the characteristic length scale and HnH_n is the nn-th physicist's Hermite polynomial.

theorem

Harmonic Oscillator Eigenfunctions ψn\psi_n are members of the Hilbert space

#eigenfunction_memHS

For any natural number nNn \in \mathbb{N}, the nn-th eigenfunction ψn:RC\psi_n: \mathbb{R} \to \mathbb{C} of the one-dimensional harmonic oscillator belongs to the Hilbert space (denoted as `MemHS`, typically corresponding to the space of square-integrable functions L2(R)L^2(\mathbb{R})). The eigenfunction is defined as: ψn(x)=12nn!πξHn(xξ)ex22ξ2\psi_n(x) = \frac{1}{\sqrt{2^n n! \sqrt{\pi} \xi}} H_n\left(\frac{x}{\xi}\right) e^{-\frac{x^2}{2\xi^2}} where ξ\xi is the characteristic length scale and HnH_n is the nn-th physicist's Hermite polynomial.

theorem

The Harmonic Oscillator Eigenfunctions ψn\psi_n are Differentiable at every point xx

#eigenfunction_differentiableAt

For any natural number nn and any real number xx, the nn-th eigenfunction ψn:RC\psi_n: \mathbb{R} \to \mathbb{C} of the one-dimensional harmonic oscillator is differentiable at xx. The eigenfunction is defined as: ψn(x)=12nn!πξHn(xξ)ex22ξ2\psi_n(x) = \frac{1}{\sqrt{2^n n! \sqrt{\pi} \xi}} H_n\left(\frac{x}{\xi}\right) e^{-\frac{x^2}{2\xi^2}} where ξ\xi is the characteristic length scale and HnH_n is the nn-th physicist's Hermite polynomial.

theorem

Harmonic Oscillator Eigenfunctions ψn\psi_n are Continuous

#eigenfunction_continuous

For any natural number nn, the nn-th eigenfunction ψn:RC\psi_n: \mathbb{R} \to \mathbb{C} of the one-dimensional harmonic oscillator is a continuous function. The eigenfunction is defined as: ψn(x)=12nn!πξHn(xξ)ex22ξ2\psi_n(x) = \frac{1}{\sqrt{2^n n! \sqrt{\pi} \xi}} H_n\left(\frac{x}{\xi}\right) e^{-\frac{x^2}{2\xi^2}} where ξ\xi is the characteristic length scale and HnH_n is the nn-th physicist's Hermite polynomial.

theorem

The Parity of the nn-th Harmonic Oscillator Eigenfunction ψn\psi_n is (1)n(-1)^n

#eigenfunction_parity

For any natural number nn, the nn-th eigenfunction ψn:RC\psi_n: \mathbb{R} \to \mathbb{C} of the one-dimensional harmonic oscillator is an eigenfunction of the parity operator P^\hat{P} with eigenvalue (1)n(-1)^n. That is, P^ψn=(1)nψn\hat{P} \psi_n = (-1)^n \psi_n where the parity operator P^\hat{P} is defined as (P^ψ)(x)=ψ(x)(\hat{P} \psi)(x) = \psi(-x), and the eigenfunction ψn\psi_n is given by: ψn(x)=12nn!πξHn(xξ)ex22ξ2\psi_n(x) = \frac{1}{\sqrt{2^n n! \sqrt{\pi} \xi}} H_n\left(\frac{x}{\xi}\right) e^{-\frac{x^2}{2\xi^2}} with ξ\xi being the characteristic length scale and HnH_n being the nn-th physicist's Hermite polynomial.

theorem

Product formula for harmonic oscillator eigenfunctions ψn\psi_n and ψp\psi_p

#eigenfunction_mul

For any natural numbers nn and pp, the product of the nn-th and pp-th eigenfunctions ψn(x)\psi_n(x) and ψp(x)\psi_p(x) of the one-dimensional harmonic oscillator at position xRx \in \mathbb{R} is given by: ψn(x)ψp(x)=12nn!12pp!1πξHn(xξ)Hp(xξ)exp(x2ξ2)\psi_n(x) \psi_p(x) = \frac{1}{\sqrt{2^n n!}} \frac{1}{\sqrt{2^p p!}} \frac{1}{\sqrt{\pi} \xi} H_n\left(\frac{x}{\xi}\right) H_p\left(\frac{x}{\xi}\right) \exp\left(-\frac{x^2}{\xi^2}\right) where ξ\xi is the characteristic length scale and HkH_k denotes the kk-th physicist's Hermite polynomial.

theorem

Square of the harmonic oscillator eigenfunction ψn(x)2\psi_n(x)^2

#eigenfunction_mul_self

For any natural number nn, the square of the nn-th eigenfunction ψn(x)\psi_n(x) of the one-dimensional harmonic oscillator at position xRx \in \mathbb{R} is given by: ψn(x)2=12nn!πξHn(xξ)2exp(x2ξ2)\psi_n(x)^2 = \frac{1}{2^n n! \sqrt{\pi} \xi} H_n\left(\frac{x}{\xi}\right)^2 \exp\left(-\frac{x^2}{\xi^2}\right) where ξ\xi is the characteristic length scale and HnH_n denotes the nn-th physicist's Hermite polynomial.

theorem

Harmonic Oscillator Eigenfunctions ψn\psi_n are Normalized: ψn,ψn=1\langle \psi_n, \psi_n \rangle = 1

#eigenfunction_normalized

For any natural number nNn \in \mathbb{N}, the nn-th eigenfunction ψn\psi_n of the one-dimensional harmonic oscillator is normalized. That is, the inner product of ψn\psi_n with itself in the Hilbert space is equal to 1: ψn,ψn=1\langle \psi_n, \psi_n \rangle = 1 Here, ψn\psi_n is the nn-th eigenfunction defined in terms of Hermite polynomials and the characteristic length scale ξ\xi.

theorem

Harmonic Oscillator Eigenfunctions are Orthogonal for npn \neq p

#eigenfunction_orthogonal

For any distinct natural numbers nn and pp (npn \neq p), the nn-th and pp-th eigenfunctions ψn\psi_n and ψp\psi_p of the one-dimensional quantum harmonic oscillator are orthogonal. That is, their inner product in the Hilbert space is zero: ψn,ψp=0\langle \psi_n, \psi_p \rangle = 0 where ψk\psi_k is the kk-th eigenfunction defined using Hermite polynomials and a Gaussian envelope.

theorem

Harmonic Oscillator Eigenfunctions are Orthonormal

#eigenfunction_orthonormal

The eigenfunctions (ψn)nN(\psi_n)_{n \in \mathbb{N}} of the one-dimensional quantum harmonic oscillator form an orthonormal set in the Hilbert space. That is, for any natural numbers n,mNn, m \in \mathbb{N}, their complex inner product satisfies: ψn,ψm=δnm\langle \psi_n, \psi_m \rangle = \delta_{nm} where δnm\delta_{nm} is the Kronecker delta, which is equal to 11 if n=mn = m and 00 otherwise.

theorem

The eigenfunctions ψn\psi_n are linearly independent

#eigenfunction_linearIndependent

The sequence of eigenfunctions (ψn)nN(\psi_n)_{n \in \mathbb{N}} of the one-dimensional quantum harmonic oscillator is linearly independent over the field of complex numbers C\mathbb{C}. Each eigenfunction ψn\psi_n is an element of the Hilbert space of the system.