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Weber Functions


Although Bessel functions of the second kind are sometimes called Weber functions, Abramowitz and Stegun (1972) define a separate Weber function as

 E_nu(z)=1/piint_0^pisin(nutheta-zsintheta)dtheta.
(1)

These function may also be written as

 E_nu(z)=sin(1/2pinu)_1F^~_2(1;1/2(2-nu),1/2(2+nu);-1/4z^2)-1/2zcos(1/2pinu)_1F^~_2(1;1/2(3-nu),1/2(nu+3);-1/4z^2),
(2)

where _1F^~_2(a;b,c;z) is a regularized hypergeometric function.

This function is implemented in the Wolfram Language as WeberE[nu, z] and is an analog of the Anger function.

Special values for real x include

E_0(x)=-H_0(x)
(3)
E_1(x)=H_1(|x|)
(4)
E_2(x)=H_0(x)-(2H_1(x))/x
(5)
E_3(x)=-H_(-1)(x)-(4H_2(x))/x+8/(3pi),
(6)

where H_n(z) is a Struve function.

Letting zeta_n=e^(2pii/n) be a root of unity, another set of Weber functions is defined as

f(tau)=(eta(1/2(tau+1)))/(zeta_(48)eta(tau))
(7)
f_1(tau)=(eta(1/2tau))/(eta(tau))
(8)
f_2(tau)=sqrt(2)(eta(2tau))/(eta(tau))
(9)
gamma_2(tau)=(f^(24)(tau)-16)/(f^8(tau))
(10)
gamma_3(tau)=([f^(24)(tau)+8][f_1^8(tau)-f_2^8(tau)])/(f^8(tau))
(11)

(Weber 1902, Atkin and Morain 1993), where eta(tau) is the Dedekind eta function and tau is the half-period ratio. These functions are related to the Ramanujan g- and G-functions and the elliptic lambda function.

The Weber functions satisfy the identities

f(tau+1)=(f_1(tau))/(zeta_(48))
(12)
f_1(tau+1)=(f(tau))/(zeta_(48))
(13)
f_2(tau+1)=zeta_(24)f_2(tau)
(14)
f(-1/tau)=f(tau)
(15)
f_1(-1/tau)=f_2(tau)
(16)
f_2(-1/tau)=f_1(tau)
(17)

(Weber 1902, Atkin and Morain 1993).


See also

Anger Function, Bessel Function of the Second Kind, Dedekind Eta Function, Elliptic Lambda Function, j-Function, Jacobi Identities, Jacobi Triple Product, Klein's Absolute Invariant, Modified Struve Function, Ramanujan g- and G-Functions, Q-Function, Struve Function

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References

Abramowitz, M. and Stegun, I. A. (Eds.). "Anger and Weber Functions." §12.3 in Handbook of Mathematical Functions with Formulas, Graphs, and Mathematical Tables, 9th printing. New York: Dover, pp. 498-499, 1972.Atkin, A. O. L. and Morain, F. "Elliptic Curves and Primality Proving." Math. Comput. 61, 29-68, 1993.Borwein, J. M. and Borwein, P. B. Pi & the AGM: A Study in Analytic Number Theory and Computational Complexity. New York: Wiley, pp. 68-69, 1987.Prudnikov, A. P.; Marichev, O. I.; and Brychkov, Yu. A. "The Anger Function J_nu(x) and Weber Function E_nu(x)." §1.5 in Integrals and Series, Vol. 3: More Special Functions. Newark, NJ: Gordon and Breach, p. 28, 1990.Weber, H. Lehrbuch der Algebra, Vols. I-II. New York: Chelsea, pp. 113-114, 1902.Weng, A. "Class Polynomials of CM-Fields. http://www.exp-math.uni-essen.de/zahlentheorie/classpol/class.html.

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Weber Functions

Cite this as:

Weisstein, Eric W. "Weber Functions." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/WeberFunctions.html

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