Some divided difference inequalities for n-convex functions

Using results from the theory of B-splines, various inequalities involving the nth order divided differences of a function f with convex nth derivative are proved; notably, $\text{f}{}^{\mathrm{(n)}}\text{(z)}\text{n! ? [x}{}_0\text{,…, x}{}_{\mathrm{n}}\text{]f}\text{?}\text{∑}{}_{\mathrm{i\; =\; 0}}{}^{\mathrm{n}}\text{(f}{}^{\mathrm{(n)}}\text{(x}{}_{\mathrm{i}}\text{)}\text{(n + 1)!)}$, where z is the center of mass $\text{(}\text{1}\text{(n + 1))}\text{∑}{}_{\mathrm{i\; =\; 0}}{}^{\mathrm{n}}\text{x}{}_{\mathrm{i}}$.     

Generalized Hadamard's inequality and r-convex functions in Carnot groups

In this paper, we establish a generalization of Hadamard's inequality to r-convex functions on Carnot groups.     

Some properties of semi-E-convex functions

In this paper, we show that Theorems 4.2, 4.3 and 4.6 in [Youness, J. Optim. Theory Appl. 102 (1999) 439-450] are incorrect by giving some counterexamples. We introduce a new class of semi-E-convex function and discuss some its basic properties.     

Some inequalities of Hermite-Hadamard type for s-convex functions

In this paper several inequalities of the left-hand side of Hermite-Hadamard’s inequality are obtained for s-convex functions.     

Some properties of functions with nonzero order n divided difference

We consider the properties of functions of class K _n (D). This class consists of analytic functions F(z) in a domain D whose nth divided difference does not vanish in D. We study some relation of functions of class K _n (D) to Chebyshev systems, consider a few properties of an operator related to a fractional linear transformation of the unit disk, and estimate Taylor series coefficients.     

A functional inequality for real-analytic functions

Summary Forf ( C ⁿ() and 0 t x letJ _n (f, t, x) = (–1)ⁿ f(–x)f ⁽ⁿ⁾(t) +f(x)f ⁽ⁿ⁾ (–t). We prove that the only real-analytic functions satisfyingJ _n (f, t, x) 0 for alln = 0, 1, 2, are the exponential functionsf(x) = c e ^x,c, . Further we present a nontrivial class of real-analytic functions satisfying the inequalitiesJ ₀ (f, x, x) 0 and ₀ ^x (x – t)^{n – 1}J_n(f, t, x)dt 0 (n 1).     

A localization inequality for set functions

We prove the following theorem, which is an analog for discrete set functions of a geometric result of Lovász and Simonovits. Given two real-valued set functions f₁,f₂ defined on the subsets of a finite set S, satisfying for i∈{1,2}, there exists a positive multiplicative set function μ over S and two subsets A,B⊆S such that for i∈{1,2}μ(A)f_i(A)+μ(B)f_i(B)+μ(A∪B)f_i(A∪B)+μ(A∩B)f_i(A∩B)?0. The Ahlswede-Daykin four function theorem can be deduced easily from this.     

A new inequality for entire functions

We prove that, if f(z) is an entire function and ¦f(z)¦ (A₁ + A₂ ¦z¦ⁿ) exp[ax² + by² + cx + dy], then there are numbers C₁, C₂ 0, depending only on n, A₁, A₂, a, b, c, and d such that ¦f′(z)¦ (C₁ + C₂ ¦z¦^{n + 1}) exp(ax² + by² + cx + dy).     

A new inequality for symmetric functions

Let x_i ≥ 0, y_i ≥ 0 for i = 1,…, n; and let a_j(x) be the elementary symmetric function of n variables given by a_j(x) = ∑_{1 ≤ ii < … <ij ≤ n}x_ii … x_ij. Define the partical ordering x <y if a_j(x) ≤ a_j(y), j = 1,… n. We show that $\text{x}\text{\$}\text{?}\text{y ? x}{}^{\mathrm{\alpha }}\text{\$}\text{?}\text{y}{}^{\mathrm{\alpha }}\text{, 0}\text{\$}\text{?}\text{α ≤ 1}$, where {x^α}_i = x^α_i. We also give a necessary and sufficient condition on a function f(t) such that x <y ? f(x) <f(y). Both results depend crucially on the following: If x <y there exists a piecewise differentiable path z(t), with z_i(t) ≥ 0, such that z(0) = x, z(1) = y, and z(s) <z(t) if 0 ≤ s ≤ t ≤ 1.     

Complete monotonicity of a function involving the divided difference of digamma functions

In the paper, necessary and sufficient conditions are provided for a function involving the divided difference of two psi functions to be completely monotonic. Consequently, a class of inequalities for sums are presented, the logarithmically complete monotonicity of a function involving the ratio of two gamma functions are derived, and two double inequalities for bounding the ratio of two gamma functions are discovered.     

A majorization inequality for Wright-convex functions revisited

We give an elementary proof of a majorization inequality concerning Wright-convex functions.     

A sharpened Strichartz inequality for radial functions

We prove a new sharpened version of the Strichartz inequality for radial solutions of the Schrödinger equation in two dimensions. We establish an improved upper bound for functions that nearly extremize the inequality, with a negative second term that measures the distance from the initial data to Gaussians.