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35 Functions of Matrix ArgumentNotation

§35.1 Special Notation

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

All matrices are of order m×m, unless specified otherwise. All fractional or complex powers are principal values.

a,b complex variables.
j,k,p,q nonnegative integers.
m positive integer.
[a]κ partitional shifted factorial (§35.4(i)).
𝟎 zero matrix.
𝐈 identity matrix.
𝓢 space of all real symmetric matrices.
𝐒,𝐓,𝐗 real symmetric matrices.
tr⁡𝐗 trace of 𝐗.
etr⁡(𝐗) exp⁡(tr⁡𝐗).
|𝐗| determinant of 𝐗 (except when m=1 where it means either determinant or absolute value, depending on the context).
|(𝐗)j| jth principal minor of 𝐗.
xj,k (j,k)th element of 𝐗.
d𝐗 ∏1≤j≤k≤mdxj,k.
𝛀 space of positive-definite real symmetric matrices.
t1,…,tm eigenvalues of 𝐓.
‖𝐓‖ spectral norm of 𝐓.
𝐗>𝐓 𝐗−𝐓 is positive definite. Similarly, 𝐓<𝐗 is equivalent.
𝐙 complex symmetric matrix.
f⁡(𝐗) complex-valued function with 𝐗∈𝛀.
𝐎⁡(m) space of orthogonal matrices.
𝐇 orthogonal matrix.
d⁢𝐇 normalized Haar measure on 𝐎⁡(m).
Zκ⁡(𝐓) zonal polynomials.

The main functions treated in this chapter are the multivariate gamma and beta functions, respectively Γm⁡(a) and Bm⁡(a,b), and the special functions of matrix argument: Bessel (of the first kind) Aν⁡(𝐓) and (of the second kind) Bν⁡(𝐓); confluent hypergeometric (of the first kind) F11⁡(a;b;𝐓) or F11⁡(ab;𝐓) and (of the second kind) Ψ⁡(a;b;𝐓); Gaussian hypergeometric F12⁡(a1,a2;b;𝐓) or F12⁡(a1,a2b;𝐓); generalized hypergeometric Fqp⁡(a1,…,ap;b1,…,bq;𝐓) or Fqp⁡(a1,…,apb1,…,bq;𝐓).

An alternative notation for the multivariate gamma function is Πm⁡(a)=Γm⁡(a+12⁢(m+1)) (Herz (1955, p. 480)). Related notations for the Bessel functions are 𝒥ν+12⁢(m+1)⁡(𝐓)=Aν⁡(𝐓)/Aν⁡(𝟎) (Faraut and Korányi (1994, pp. 320–329)), Km⁡(0,…,0,ν|𝐒,𝐓)=|𝐓|ν⁢Bν⁡(𝐒⁢𝐓) (Terras (1988, pp. 49–64)), and 𝒦ν⁡(𝐓)=|𝐓|ν⁢Bν⁡(𝐒⁢𝐓) (Faraut and Korányi (1994, pp. 357–358)).