28 Mathieu Functions and Hill’s EquationNotation

§28.1 Special Notation

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

m,n integers.
x,y real variables.
z=x+i⁢y complex variable.
ν order of the Mathieu function or modified Mathieu function. (When ν is an integer it is often replaced by n.)
δ arbitrary small positive number.
a,q,h real or complex parameters of Mathieu’s equation with q=h2.
primes unless indicated otherwise, derivatives with respect to the argument

The main functions treated in this chapter are the Mathieu functions

ceν⁡(z,q), seν⁡(z,q), fen⁡(z,q), gen⁡(z,q), meν⁡(z,q),

and the modified Mathieu functions

Ceν⁡(z,q), Seν⁡(z,q), Fen⁡(z,q), Gen⁡(z,q),
Meν⁡(z,q), Mν(j)⁡(z,h), Mcn(j)⁡(z,h), Msn(j)⁡(z,h),
Ien⁡(z,h), Ion⁡(z,h), Ken⁡(z,h), Kon⁡(z,h).

The functions Mcn(j)⁡(z,h) and Msn(j)⁡(z,h) are also known as the radial Mathieu functions.

The eigenvalues of Mathieu’s equation are denoted by

an⁡(q),
bn⁡(q),
λν⁡(q).

The notation for the joining factors is

ge,n⁡(h),
go,n⁡(h),
fe,n⁡(h),
fo,n⁡(h).

Alternative notations for the parameters a and q are shown in Table 28.1.1.

Table 28.1.1: Notations for parameters in Mathieu’s equation.
Reference a q
Erdélyi et al. (1955) h θ
Meixner and Schäfke (1954) λ h2
Moon and Spencer (1971) λ q
Strutt (1932) λ h2
Whittaker and Watson (1927) a 8⁢q

Alternative notations for the functions are as follows.

Arscott (1964b) and McLachlan (1947)

Feyn⁡(z,q) =12⁢π⁢ge,n⁡(h)⁢cen⁡(0,q)⁢Mcn(2)⁡(z,h),
Men(1,2)⁡(z,q) =12⁢π⁢ge,n⁡(h)⁢cen⁡(0,q)⁢Mcn(3,4)⁡(z,h),
Geyn⁡(z,q) =12⁢π⁢go,n⁡(h)⁢sen′⁡(0,q)⁢Msn(2)⁡(z,h),
Nen(1,2)⁡(z,q) =12⁢π⁢go,n⁡(h)⁢sen′⁡(0,q)⁢Msn(3,4)⁡(z,h).

Arscott (1964b) also uses −i⁢μ for ν.

Campbell (1955)

inn =fen, cehn =Cen, inhn =Fen,
jnn =gen, sehn =Sen, jnhn =Gen.

Abramowitz and Stegun (1964, Chapter 20)

Fν⁡(z)=Meν⁡(z,q).

National Bureau of Standards (1967)

With s=4⁢q,

Sen⁡(s,z) =cen⁡(z,q)cen⁡(0,q),
Son⁡(s,z) =sen⁡(z,q)sen′⁡(0,q).

Stratton et al. (1941)

With c=2⁢q,

Sen⁡(c,z) =cen⁡(z,q)cen⁡(0,q),
Son⁡(c,z) =sen⁡(z,q)sen′⁡(0,q).

Zhang and Jin (1996)

The radial functions Mcn(j)⁡(z,h) and Msn(j)⁡(z,h) are denoted by Mcn(j)⁡(z,q) and Msn(j)⁡(z,q), respectively.