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q-Gamma Function


A q-analog of the gamma function defined by

 Gamma_q(x)=((q;q)_infty)/((q^x;q)_infty)(1-q)^(1-x),
(1)

where (x,q)_infty is a q-Pochhammer symbol (Koepf 1998, p. 26; Koekoek and Swarttouw 1998). The q-gamma function satisfies

 lim_(q->1^-)Gamma_q(x)=Gamma(x),
(2)

where Gamma(z) is the gamma function (Andrews 1986).

The q-gamma function is implemented in the Wolfram Language as QGamma[z, q].

The q-gamma function satisfies the functional equation

 Gamma_q(z+1)=(1-q^z)/(1-q)Gamma_q(z)
(3)

with Gamma_q(1)=1 (Koekoek and Swarttouw 1998, p. 10), which simplifies to

 Gamma(z+1)=zGamma(z)
(4)

as q->1^-. A curious identity for the functional equation

 f(a-b)f(a-c)f(a-d)f(a-e)-f(b)f(c)f(d)f(e) 
 =q^bf(a)f(a-b-c)f(a-b-d)f(a-b-e),
(5)

where

 b+c+d+e=2a
(6)

is given by

 f(alpha)={sin(kalpha)   for q=1; 1/(Gamma_q(alpha)Gamma_q(1-alpha))   for 0<q<1,
(7)

for any k.


See also

Gamma Function, q-Beta Function, q-Factorial, q-Pochhammer Symbol

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References

Andrews, G. E. "W. Gosper's Proof that lim_(q->1^-)Gamma_q(x)=Gamma(x)." Appendix A in q-Series: Their Development and Application in Analysis, Number Theory, Combinatorics, Physics, and Computer Algebra. Providence, RI: Amer. Math. Soc., p. 11 and 109, 1986.Gasper, G. and Rahman, M. Basic Hypergeometric Series. Cambridge, England: Cambridge University Press, 1990.Koekoek, R. and Swarttouw, R. F. "The q-Gamma Function and the q-Binomial Coefficient." §0.3 in The Askey-Scheme of Hypergeometric Orthogonal Polynomials and its q-Analogue. Delft, Netherlands: Technische Universiteit Delft, Faculty of Technical Mathematics and Informatics Report 98-17, pp. 10-11, 1998.Koepf, W. Hypergeometric Summation: An Algorithmic Approach to Summation and Special Function Identities. Braunschweig, Germany: Vieweg, 1998.Wenchang, C. Problem 10226 and Solution. "A q-Trigonometric Identity." Amer. Math. Monthly 103, 175-177, 1996.

Referenced on Wolfram|Alpha

q-Gamma Function

Cite this as:

Weisstein, Eric W. "q-Gamma Function." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/q-GammaFunction.html

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