I would like to calculate the uncertainty of the nth Eigenstate of a 1-dim harmonic oscillator. To obtain the result I have to solve the integral

∫∞−∞ψ∗x2ψdx\int_{-\infty}^{\infty} \psi^* x^2 \psi \:dx with ψ(n,x)=e−x22Hn(x)π14√2nn!\psi(n,x)=\frac{e^{-\frac{x^2}{2}} H_n(x)}{\pi^{\frac{1}{4}}\sqrt{2^n n!}}, where Hn(x)H_n(x) is the Hermite polynomial (degree n) in the physicist version (as implemented in Mathematica). In Mathematica this equals to the Integral over

(2^-n E^-x^2 x^2 HermiteH[n, x]^2)/(Sqrt[Ï€] n!)

Doing this manually gives 1/2+n1/2+n, but i can’t get Mathematica to solve this integral without specifying nn. I used `

Assuptions=n âˆˆ Integers && n >= 0

Is there anyway to solve similar integrals with Mathematica?

Edit: Thanks for you answer, but I should have mentioned, that I’m looking for a way to let Mathematica solve such problems analytical.

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Closely related or a duplicate How do I evaluate a symbolic integral involving Hermite polynomials?.

– Artes

Dec 25 ’13 at 20:00

You could code up (50) or (51) from here.

– b.gatessucks

Dec 26 ’13 at 9:36

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1 Answer

1

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An easy way without struggling with the integral:

FindSequenceFunction[

Table[Integrate[(2^-n E^-x^2 x^2 HermiteH[n, x]^2)/(Sqrt[Ï€] n!), {x, -Infinity, Infinity}],

{n, 1, 5}], n]

(*

1/2 (1 + 2 n)

*)

Is there any way to let Mathematica solve this problem analytical?

– Gebbo

Dec 25 ’13 at 23:17

@Gebbo Not AFAIK

– Dr. belisarius

Dec 26 ’13 at 2:24