11. The Hermite polynomials, H,„(x), satisfy the following: į. < Hn, Hm >= Se-**H„(x)Hm(x) dx = \T2"n! 8,m: ii. Н, (х) — 2nHm-1 (x). n-: ii. Ни+1 (х) — 2хН, (х) — 2nНи-1 (х). iv. H, (x) = (–1)"e*² (e-x*). dn (e-**). dxn Using these, show: b. xe-**H„(x)Hm(x) dx = VT2"-1n! [8mn=1+ 2(n + 1)8m,n+1] -x² тп-1

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Need some help understanding Hermite polynomials for PDE

 

**Hermite Polynomials and Their Properties**

The Hermite polynomials, \( H_n(x) \), satisfy the following conditions:

1. **Orthogonality Condition:**

   \[
   \langle H_n, H_m \rangle = \int_{-\infty}^{\infty} e^{-x^2} H_n(x) H_m(x) \, dx = \sqrt{\pi} 2^n n! \, \delta_{n,m}.
   \]

   This expression represents the orthogonality of Hermite polynomials, where \(\delta_{n,m}\) is the Kronecker delta, which is 1 if \( n = m \) and 0 otherwise.

2. **Derivative Relation:**

   \[
   H'_n(x) = 2n H_{n-1}(x).
   \]

   This shows the relationship between the derivative of a Hermite polynomial and the polynomial of one lower order.

3. **Recurrence Relation:**

   \[
   H_{n+1}(x) = 2x H_n(x) - 2n H_{n-1}(x).
   \]

   This equation expresses the polynomial of order \( n+1 \) in terms of the polynomials of order \( n \) and \( n-1 \).

4. **Explicit Formula:**

   \[
   H_n(x) = (-1)^n e^{x^2} \frac{d^n}{dx^n} \left( e^{-x^2} \right).
   \]

   This formula provides a direct way to compute Hermite polynomials using differentiation.

**Using These Properties:**

Demonstrate the following integral involving Hermite polynomials:

\[
\int_{-\infty}^{\infty} x e^{-x^2} H_n(x) H_m(x) \, dx = \sqrt{\pi} 2^{n-1} n! \left[ \delta_{m,n-1} + 2(n+1) \delta_{m,n+1} \right].
\]

This expression illustrates how the integration of a product of a polynomial and a variable, weighted by a Gaussian function, results in specific coefficients that depend on the polynomial indices.
Transcribed Image Text:**Hermite Polynomials and Their Properties** The Hermite polynomials, \( H_n(x) \), satisfy the following conditions: 1. **Orthogonality Condition:** \[ \langle H_n, H_m \rangle = \int_{-\infty}^{\infty} e^{-x^2} H_n(x) H_m(x) \, dx = \sqrt{\pi} 2^n n! \, \delta_{n,m}. \] This expression represents the orthogonality of Hermite polynomials, where \(\delta_{n,m}\) is the Kronecker delta, which is 1 if \( n = m \) and 0 otherwise. 2. **Derivative Relation:** \[ H'_n(x) = 2n H_{n-1}(x). \] This shows the relationship between the derivative of a Hermite polynomial and the polynomial of one lower order. 3. **Recurrence Relation:** \[ H_{n+1}(x) = 2x H_n(x) - 2n H_{n-1}(x). \] This equation expresses the polynomial of order \( n+1 \) in terms of the polynomials of order \( n \) and \( n-1 \). 4. **Explicit Formula:** \[ H_n(x) = (-1)^n e^{x^2} \frac{d^n}{dx^n} \left( e^{-x^2} \right). \] This formula provides a direct way to compute Hermite polynomials using differentiation. **Using These Properties:** Demonstrate the following integral involving Hermite polynomials: \[ \int_{-\infty}^{\infty} x e^{-x^2} H_n(x) H_m(x) \, dx = \sqrt{\pi} 2^{n-1} n! \left[ \delta_{m,n-1} + 2(n+1) \delta_{m,n+1} \right]. \] This expression illustrates how the integration of a product of a polynomial and a variable, weighted by a Gaussian function, results in specific coefficients that depend on the polynomial indices.
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