定義
在數學中,拉蓋爾多項式定義為拉蓋爾方程的標準解。下列為拉蓋爾方程:
![拉蓋爾多項式](/img/f/033/wZwpmLwAzN4gjM1UjM3QTN1UTM1QDN5MjM5ADMwAjMwUzL1IzLzczLt92YucmbvRWdo5Cd0FmL0E2LvoDc0RHa.jpg)
![拉蓋爾多項式](/img/c/8f2/wZwpmLwIDN1EDM5AzNwMzM1UTM1QDN5MjM5ADMwAjMwUzLwczLzUzLt92YucmbvRWdo5Cd0FmLzE2LvoDc0RHa.jpg)
![拉蓋爾多項式](/img/c/8f2/wZwpmLwIDN1EDM5AzNwMzM1UTM1QDN5MjM5ADMwAjMwUzLwczLzUzLt92YucmbvRWdo5Cd0FmLzE2LvoDc0RHa.jpg)
此方程只有當n為非負時才有非平凡解。 是拉蓋爾方程的正則奇點。在 及其鄰域上為有限的級數解是
![拉蓋爾多項式](/img/5/fb1/wZwpmLzgzNwETMwATM3QTN1UTM1QDN5MjM5ADMwAjMwUzLwEzLxAzLt92YucmbvRWdo5Cd0FmLzE2LvoDc0RHa.jpg)
級數的收斂半徑為無限大。
![拉蓋爾多項式](/img/3/e98/wZwpmLxQjMzIDN2IjM3QTN1UTM1QDN5MjM5ADMwAjMwUzLyIzL2QzLt92YucmbvRWdo5Cd0FmLwE2LvoDc0RHa.jpg)
![拉蓋爾多項式](/img/8/c95/wZwpmLzETN4IzM5kTOxMzM1UTM1QDN5MjM5ADMwAjMwUzL5kzL0gzLt92YucmbvRWdo5Cd0FmLwE2LvoDc0RHa.jpg)
如n為整數,解y(x)退化為n次多項式。用適當的常數乘這些多項式,使最高次冪項成為 就叫作拉蓋爾多項式,記作 ,
拉蓋爾多項式由羅德里格公式推導出公式 ,如下:
![拉蓋爾多項式](/img/6/716/wZwpmL2czN4MzM4YDM3QTN1UTM1QDN5MjM5ADMwAjMwUzL2AzLxczLt92YucmbvRWdo5Cd0FmLzE2LvoDc0RHa.jpg)
它可以用遞推關係表達,如下:
![拉蓋爾多項式](/img/2/841/wZwpmLwgjM1gTMwYTM3QTN1UTM1QDN5MjM5ADMwAjMwUzL2EzLxUzLt92YucmbvRWdo5Cd0FmLwE2LvoDc0RHa.jpg)
![拉蓋爾多項式](/img/1/566/wZwpmLxMDNxcTMzkzM3QTN1UTM1QDN5MjM5ADMwAjMwUzL5MzLxgzLt92YucmbvRWdo5Cd0FmLzE2LvoDc0RHa.jpg)
![拉蓋爾多項式](/img/f/dcf/wZwpmL3UDMxIzN2EjM3QTN1UTM1QDN5MjM5ADMwAjMwUzLxIzLyQzLt92YucmbvRWdo5Cd0FmL0E2LvoDc0RHa.jpg)
拉蓋爾多項式的遞推關係也可以表現為 :
![拉蓋爾多項式](/img/0/68f/wZwpmLyQTM0ETNykjM3QTN1UTM1QDN5MjM5ADMwAjMwUzL5IzL2MzLt92YucmbvRWdo5Cd0FmLzE2LvoDc0RHa.jpg)
![拉蓋爾多項式](/img/2/d2c/wZwpmL2QTNxcjNyczM3QTN1UTM1QDN5MjM5ADMwAjMwUzL3MzLzQzLt92YucmbvRWdo5Cd0FmLwE2LvoDc0RHa.jpg)
此多項式是區間 上函式全體按照如下定義內積時的標準正交多項式:
![拉蓋爾多項式](/img/f/b90/wZwpmL3AzMxcjMyQTM3QTN1UTM1QDN5MjM5ADMwAjMwUzL0EzL2AzLt92YucmbvRWdo5Cd0FmL0E2LvoDc0RHa.jpg)
廣義
定義
![拉蓋爾多項式](/img/2/d2c/wZwpmL2QTNxcjNyczM3QTN1UTM1QDN5MjM5ADMwAjMwUzL3MzLzQzLt92YucmbvRWdo5Cd0FmLwE2LvoDc0RHa.jpg)
![拉蓋爾多項式](/img/b/73d/wZwpmLxEjNwMzN0YDM3QTN1UTM1QDN5MjM5ADMwAjMwUzL2AzL3AzLt92YucmbvRWdo5Cd0FmLxE2LvoDc0RHa.jpg)
![拉蓋爾多項式](/img/b/ecf/wZwpmL2IzNzUjM2UzM3QTN1UTM1QDN5MjM5ADMwAjMwUzL1MzL2gzLt92YucmbvRWdo5Cd0FmLzE2LvoDc0RHa.jpg)
稱在 上伴隨核函式 的標準正交多項式為廣義拉蓋爾多項式,記為 。廣義拉蓋爾多項式也可以由如下的羅德里格公式給出:
![拉蓋爾多項式](/img/3/90a/wZwpmLxEDO4gTNwczM3QTN1UTM1QDN5MjM5ADMwAjMwUzL3MzL2UzLt92YucmbvRWdo5Cd0FmLzE2LvoDc0RHa.jpg)
![拉蓋爾多項式](/img/1/93f/wZwpmL1EzM0gDMxMDO4EDN0UTMyITNykTO0EDMwAjMwUzLzgzL2UzLt92YucmbvRWdo5Cd0FmLwE2LvoDc0RHa.jpg)
當 時,廣義拉蓋爾多項式退化為標準拉蓋爾多項式。
廣義拉蓋爾多項式有如下解析表達式:
![拉蓋爾多項式](/img/8/beb/wZwpmL4UzN5QjN0QTM3QTN1UTM1QDN5MjM5ADMwAjMwUzL0EzL4IzLt92YucmbvRWdo5Cd0FmLxE2LvoDc0RHa.jpg)
廣義拉蓋爾多項式有如下遞推關係 :
![拉蓋爾多項式](/img/b/1da/wZwpmLxAjN1cTN0ADN3QTN1UTM1QDN5MjM5ADMwAjMwUzLwQzLxAzLt92YucmbvRWdo5Cd0FmLwE2LvoDc0RHa.jpg)
![拉蓋爾多項式](/img/4/bb7/wZwpmL4YDO1ITM0gTM3QTN1UTM1QDN5MjM5ADMwAjMwUzL4EzL1UzLt92YucmbvRWdo5Cd0FmLyE2LvoDc0RHa.jpg)
性質
![拉蓋爾多項式](/img/3/267/wZwpmL4UDN0gDM3gzM3QTN1UTM1QDN5MjM5ADMwAjMwUzL4MzL4IzLt92YucmbvRWdo5Cd0FmLxE2LvoDc0RHa.jpg)
正交性:
平方積分:
![拉蓋爾多項式](/img/8/a7b/wZwpmLzIDMxYjNwYTM3QTN1UTM1QDN5MjM5ADMwAjMwUzL2EzLzMzLt92YucmbvRWdo5Cd0FmLyE2LvoDc0RHa.jpg)
相關恆等式
關於一般拉蓋爾多項式和拉蓋爾多項式,可以得到以下兩個恆等式 :
![拉蓋爾多項式](/img/1/254/wZwpmLwQzNwEzNwgDM3QTN1UTM1QDN5MjM5ADMwAjMwUzL4AzL0QzLt92YucmbvRWdo5Cd0FmLxE2LvoDc0RHa.jpg)
![拉蓋爾多項式](/img/9/564/wZwpmL0cjM3EzMzcjM3QTN1UTM1QDN5MjM5ADMwAjMwUzL3IzL2czLt92YucmbvRWdo5Cd0FmLyE2LvoDc0RHa.jpg)
![拉蓋爾多項式](/img/d/b5e/wZwpmL2ADN5YzN0cDM3QTN1UTM1QDN5MjM5ADMwAjMwUzL3AzL3IzLt92YucmbvRWdo5Cd0FmLyE2LvoDc0RHa.jpg)
![拉蓋爾多項式](/img/5/083/wZwpmL2YzM3YjNwgTM3QTN1UTM1QDN5MjM5ADMwAjMwUzL4EzLyQzLt92YucmbvRWdo5Cd0FmLxE2LvoDc0RHa.jpg)
定理1:設 是一般拉蓋爾多項式,那么, 及 ,當 時,有恆等式
![拉蓋爾多項式](/img/3/d8e/wZwpmL0YDOwITMygDM3QTN1UTM1QDN5MjM5ADMwAjMwUzL4AzLzgzLt92YucmbvRWdo5Cd0FmL0E2LvoDc0RHa.jpg)
![拉蓋爾多項式](/img/3/0f4/wZwpmLyATO2MjM0czM3QTN1UTM1QDN5MjM5ADMwAjMwUzL3MzLxgzLt92YucmbvRWdo5Cd0FmL0E2LvoDc0RHa.jpg)
其中, 。
![拉蓋爾多項式](/img/1/254/wZwpmLwQzNwEzNwgDM3QTN1UTM1QDN5MjM5ADMwAjMwUzL4AzL0QzLt92YucmbvRWdo5Cd0FmLxE2LvoDc0RHa.jpg)
![拉蓋爾多項式](/img/9/564/wZwpmL0cjM3EzMzcjM3QTN1UTM1QDN5MjM5ADMwAjMwUzL3IzL2czLt92YucmbvRWdo5Cd0FmLyE2LvoDc0RHa.jpg)
![拉蓋爾多項式](/img/d/b5e/wZwpmL2ADN5YzN0cDM3QTN1UTM1QDN5MjM5ADMwAjMwUzL3AzL3IzLt92YucmbvRWdo5Cd0FmLyE2LvoDc0RHa.jpg)
定理2:設 是拉蓋爾多項式,那么, 及 ,有恆等式
![拉蓋爾多項式](/img/3/30c/wZwpmLzYTN3QzN0QjM3QTN1UTM1QDN5MjM5ADMwAjMwUzL0IzLzczLt92YucmbvRWdo5Cd0FmLyE2LvoDc0RHa.jpg)