8 Incomplete Gamma and Related Functions8.2 Definitions and Basic Properties

§8.1 Special Notation

(For other notation see Notation for the Special Functions.)

x real variable.
z complex variable.
a,p real or complex parameters.
k,n nonnegative integers.
\delta arbitrary small positive constant.
\mathop{\Gamma\/}\nolimits\!\left(z\right) gamma function (§5.2(i)).
\mathop{\psi\/}\nolimits\!\left(z\right) {\mathop{\Gamma\/}\nolimits^{{\prime}}}\!\left(z\right)/\mathop{\Gamma\/}\nolimits\!\left(z\right).

Unless otherwise indicated, primes denote derivatives with respect to the argument.

The functions treated in this chapter are the incomplete gamma functions \mathop{\gamma\/}\nolimits\!\left(a,z\right), \mathop{\Gamma\/}\nolimits\!\left(a,z\right), \mathop{\gamma^{{*}}\/}\nolimits\!\left(a,z\right), \mathop{P\/}\nolimits\!\left(a,z\right), and \mathop{Q\/}\nolimits\!\left(a,z\right); the incomplete beta functions \mathop{\mathrm{B}_{{x}}\/}\nolimits\!\left(a,b\right) and \mathop{I_{{x}}\/}\nolimits\!\left(a,b\right); the generalized exponential integral \mathop{E_{{p}}\/}\nolimits\!\left(z\right); the generalized sine and cosine integrals \mathop{\mathrm{si}\/}\nolimits\!\left(a,z\right), \mathop{\mathrm{ci}\/}\nolimits\!\left(a,z\right), \mathop{\mathrm{Si}\/}\nolimits\!\left(a,z\right), and \mathop{\mathrm{Ci}\/}\nolimits\!\left(a,z\right).

Alternative notations include: Prym’s functions P_{z}(a)=\mathop{\gamma\/}\nolimits\!\left(a,z\right), Q_{z}(a)=\mathop{\Gamma\/}\nolimits\!\left(a,z\right), Nielsen (1906a, pp. 25–26), Batchelder (1967, p. 63); (a,z)!=\mathop{\gamma\/}\nolimits\!\left(a+1,z\right), [a,z]!=\mathop{\Gamma\/}\nolimits\!\left(a+1,z\right), Dingle (1973); B(a,b,x)=\mathop{\mathrm{B}_{{x}}\/}\nolimits\!\left(a,b\right), I(a,b,x)=\mathop{I_{{x}}\/}\nolimits\!\left(a,b\right), Magnus et al. (1966); \mathop{\mathrm{Si}\/}\nolimits\!\left(a,x\right)\to\mathop{\mathrm{Si}\/}\nolimits\!\left(1-a,x\right), \mathop{\mathrm{Ci}\/}\nolimits\!\left(a,x\right)\to\mathop{\mathrm{Ci}\/}\nolimits\!\left(1-a,x\right), Luke (1975).