Modular Equations and Distortion Functions

Modular equations occur in number theory, but it is less known that such equations also occur in the study of deformation properties of quasiconformal mappings. The authors study two important plane quasiconformal distortion functions, obtaining monotonicity and convexity properties, and finding sharp bounds for them. Applications are provided that relate to the quasiconformal Schwarz Lemma and to Schottky's Theorem. These results also yield new bounds for singular values of complete elliptic integrals.Comment: 23 page

Inequalities for Means

AbstractA monotone form of L′Hospital′s rule is obtained and applied to derive inequalities between the arithmetic-geometric mean of Gauss, the logarithmic mean, and Stolarsky′s identric mean. Some related inequalities are given for complete elliptic integrals

Bounds for Quasiconformal Distortion Functions

AbstractSeveral new inequalities are proved for the distortion function ϕK(r) appearing in the quasiconformal Schwarz lemma. Other related special functions are studied and applications are given to quasiconformal maps in the plane. Some open problems are solved, too

Generalized convexity and inequalities

AbstractLet R+=(0,∞) and let M be the family of all mean values of two numbers in R+ (some examples are the arithmetic, geometric, and harmonic means). Given m1,m2∈M, we say that a function f:R+→R+ is (m1,m2)-convex if f(m1(x,y))⩽m2(f(x),f(y)) for all x,y∈R+. The usual convexity is the special case when both mean values are arithmetic means. We study the dependence of (m1,m2)-convexity on m1 and m2 and give sufficient conditions for (m1,m2)-convexity of functions defined by Maclaurin series. The criteria involve the Maclaurin coefficients. Our results yield a class of new inequalities for several special functions such as the Gaussian hypergeometric function and a generalized Bessel function