About the Project
15 Hypergeometric FunctionProperties

§15.5 Derivatives and Contiguous Functions

Contents
  1. §15.5(i) Differentiation Formulas
  2. §15.5(ii) Contiguous Functions

§15.5(i) Differentiation Formulas

15.5.1 ddzF(a,b;c;z)=abcF(a+1,b+1;c+1;z),
15.5.2 dndznF(a,b;c;z)=(a)n(b)n(c)nF(a+n,b+n;c+n;z).
15.5.3 (zddzz)n(za1F(a,b;c;z))=(a)nza+n1F(a+n,b;c;z).
15.5.4 dndzn(zc1F(a,b;c;z))=(cn)nzcn1F(a,b;cn;z).
15.5.5 (zddzz)n(zca1(1z)a+bcF(a,b;c;z))=(ca)nzca+n1(1z)an+bcF(an,b;c;z).
15.5.6 dndzn((1z)a+bcF(a,b;c;z))=(ca)n(cb)n(c)n(1z)a+bcnF(a,b;c+n;z).
15.5.7 ((1z)ddz(1z))n((1z)a1F(a,b;c;z))=(1)n(a)n(cb)n(c)n(1z)a+n1F(a+n,b;c+n;z).
15.5.8 ((1z)ddz(1z))n(zc1(1z)bcF(a,b;c;z))=(cn)nzcn1(1z)bc+nF(an,b;cn;z).
15.5.9 dndzn(zc1(1z)a+bcF(a,b;c;z))=(cn)nzcn1(1z)a+bcnF(an,bn;cn;z).

Other versions of several of the identities in this subsection can be constructed with the aid of the operator identity

15.5.10 (zddzz)n=zndndznzn,
n=1,2,3,.

See Erdélyi et al. (1953a, pp. 102–103).

§15.5(ii) Contiguous Functions

The six functions F(a±1,b;c;z), F(a,b±1;c;z), F(a,b;c±1;z) are said to be contiguous to F(a,b;c;z).

15.5.11 (ca)F(a1,b;c;z)+(2ac+(ba)z)F(a,b;c;z)+a(z1)F(a+1,b;c;z) =0,
15.5.12 (ba)F(a,b;c;z)+aF(a+1,b;c;z)bF(a,b+1;c;z) =0,
15.5.13 (cab)F(a,b;c;z)+a(1z)F(a+1,b;c;z)(cb)F(a,b1;c;z) =0,
15.5.14 c(a+(bc)z)F(a,b;c;z)ac(1z)F(a+1,b;c;z)+(ca)(cb)zF(a,b;c+1;z) =0,
15.5.15 (ca1)F(a,b;c;z)+aF(a+1,b;c;z)(c1)F(a,b;c1;z) =0,
15.5.16 c(1z)F(a,b;c;z)cF(a1,b;c;z)+(cb)zF(a,b;c+1;z) =0,
15.5.16_5 F(a,b;c;z)F(a1,b;c;z)(b/c)zF(a,b+1;c+1;z) =0,
15.5.17 (a1+(b+1c)z)F(a,b;c;z)+(ca)F(a1,b;c;z)(c1)(1z)F(a,b;c1;z) =0,
15.5.18 c(c1)(z1)F(a,b;c1;z)+c(c1(2cab1)z)F(a,b;c;z)+(ca)(cb)zF(a,b;c+1;z) =0.

By repeated applications of (15.5.11)–(15.5.18) any function F(a+k,b+;c+m;z), in which k,,m are integers, can be expressed as a linear combination of F(a,b;c;z) and any one of its contiguous functions, with coefficients that are rational functions of a,b,c, and z.

An equivalent equation to the hypergeometric differential equation (15.10.1) is

15.5.19 z(1z)(a+1)(b+1)F(a+2,b+2;c+2;z)+(c(a+b+1)z)(c+1)F(a+1,b+1;c+1;z)c(c+1)F(a,b;c;z)=0.

Further contiguous relations include:

15.5.20 z(1z)(dF(a,b;c;z)/dz)=(ca)F(a1,b;c;z)+(ac+bz)F(a,b;c;z)=(cb)F(a,b1;c;z)+(bc+az)F(a,b;c;z),
15.5.21 c(1z)(dF(a,b;c;z)/dz)=(ca)(cb)F(a,b;c+1;z)+c(a+bc)F(a,b;c;z).
pFad - Phonifier reborn

Pfad - The Proxy pFad of © 2024 Garber Painting. All rights reserved.

Note: This service is not intended for secure transactions such as banking, social media, email, or purchasing. Use at your own risk. We assume no liability whatsoever for broken pages.


Alternative Proxies:

Alternative Proxy

pFad Proxy

pFad v3 Proxy

pFad v4 Proxy