A short proof of the generalized Littlewood Tauberian theorem

In this work we give an alternative proof of the generalized Littlewood Tauberian theorem for the Abel summability method using a corollary to Karamata’s Main Theorem [J. Karamata, Über die Hardy–Littlewoodschen Umkehrungen des Abelschen Stetigkeitssatzes, Math. Z. 32 (1930) 319–320].     

On summability of Fourier coefficients of functions from Lebesgue space

In this paper we state new theorems of Hardy–Littlewood type for functions with general monotone Fourier coefficients. Sharpness of stated results is discusses.     

Sharp Sobolev inequalities in Lorentz spaces for a mean oscillation

We exhibit the optimal constant for Sobolev inequalities in Lorentz spaces for a mean oscillation, and its relation with a boundedness of the Hardy–Littlewood maximal operator in Sobolev spaces. Some applications to a scale invariant form of Hardy?s inequality in a limiting case are also considered.     

Stochastic dominance: A bibliographical rectification and a restatement of whitmore's theorem

The aim of this note is to make clear that the fundamental theorem on stochastic dominance of degree two was discovered in 1932 by Karamata. Apart from this historical rectification, it is interesting to remark that the proof is simple and elegant and can be used to characterize stochastic dominance of any order. We give a simple proof along these lines of Whitmore's theorem about third degree stochastic dominance.     

Dixmier traces are weak dense in the set of all fully symmetric traces

We extend Dixmier's construction of singular traces (see [2]) to arbitrary fully symmetric operator ideals. In fact, we show that the set of Dixmier traces is weak^? dense in the set of all fully symmetric traces (that is, those traces which respect Hardy–Littlewood submajorization). Our results complement and extend earlier work of Wodzicki [22].     

A Tauberian theorem for Cesàro summability of integrals

In this paper we give a proof of the generalized Littlewood Tauberian theorem for Cesàro summability of improper integrals.     

Closed covers of compact convex polyhedra

Further generalizations of the Knaster-Kuratowski-Mazurkiewicz type theorems are presented. Also given is a new proof of David Gale's theorem on a family ofn closed covers of a simplex.The authors would like to thank Richard P. McLean for his valuable suggestions. A part of this paper was completed during Tatsuro Ichiishi's visit to Instytut Podstaw Informatyki, Polskiej Akademii Nauk (Polish Academy of Sciences), Warsaw, Poland, in early September 1990. Financial supports from the Polish Academy of Sciences and from the Ohio State University are gratefully acknowledged.     

A Generalization of Vinogradov's Mean Value Theorem

We obtain new upper bounds for the number of integral solutionsof a complete system of symmetric equations, which may be viewedas a multi-dimensional version of the system considered in Vinogradov'smean value theorem. We then use these bounds to obtain Weyl-typeestimates for an associated exponential sum in several variables.Finally, we apply the Hardy–Littlewood method to obtainasymptotic formulas for the number of solutions of the Vinogradov-typesystem and also of a related system connected to the problemof finding linear spaces on hypersurfaces. 2000 MathematicsSubject Classification 11D45, 11D72, 11L07, 11P55.     

Optimality of the quantified Ingham–Karamata theorem for operator semigroups with general resolvent growth

We prove that a general version of the quantified Ingham–Karamata theorem for $$C_0$$-semigroups is sharp under mild conditions on the resolvent growth, thus generalising the results contained in a recent paper by the same authors. It follows in particular that the well-known Batty–Duyckaerts theorem is optimal even for bounded $$C_0$$-semigroups whose generator has subpolynomial resolvent growth. Our proof is based on an elegant application of the open mapping theorem, which we complement by a crucial technical lemma allowing us to strengthen our earlier results.     

Distributional versions of littlewood’s Tauberian theorem

We provide several general versions of Littlewood’s Tauberian theorem. These versions are applicable to Laplace transforms of Schwartz distributions. We employ two types of Tauberian hypotheses; the first kind involves distributional boundedness, while the second type imposes a one-sided assumption on the Cesàro behavior of the distribution. We apply these Tauberian results to deduce a number of Tauberian theorems for power series and Stieltjes integrals where Cesàro summability follows from Abel summability. We also use our general results to give a new simple proof of the classical Littlewood one-sided Tauberian theorem for power series.     

Two applications of a consistency theorem for systems of linear inequalities

A consistency criterion for systems of linear inequalities is applied to prove an existence theorem for non-negative matrices with restricted row sums, column sums and diagonal elements. As another application of the consistency criterion, a surprisingly short proof of a theorem of Hardy, Littlewood and Pólya is given.     

On moduli of smoothness and <Emphasis Type="Italic">K</Emphasis>-functionals of fractional order in the Hardy spaces

We prove the equivalence of special moduli of smoothness and K-functionals of fractional order in the space H _p , p > 0. As applications, we obtain an analog of the Hardy–Littlewood theorem and the sharp estimates of the rate of approximation of functions by generalized Bochner–Riesz means.     

The multisublinear maximal type operators in Banach function lattices

The main aim of this paper is to study a general multisublinear operators generated by quasi-concave functions between weighted Banach function lattices. These operators, in particular, generalize the Hardy–Littlewood and fractional maximal functions playing an important role in harmonic analysis. We prove that under some general geometrical assumptions on Banach function lattices two-weight weak type and also strong type estimates for these operators are true. To derive the main results of this paper we characterize the strong type estimate for a variant of multilinear averaging operators. As special cases we provide boundedness results for fractional maximal operators in concrete function spaces.     

On a tauberian theorem of Hardy and Littlewood

In this paper, we give a simple alternative proof of a Tauberian theorem of Hardy and Littlewood (Theorem E stated below, [3]).     

Interpolation inequalities for derivatives in variable exponent Lebesgue–Sobolev spaces

We show the interpolation inequalities for derivatives in variable exponent Lebesgue–Sobolev spaces by applying the boundedness of the Hardy–Littlewood maximal operator on L^p(⋅)$L^{p(\cdot )}$.     

An approach of majorization in spaces with a curved geometry

The Hardy–Littlewood–Pólya majorization theorem is extended to the framework of some spaces with a curved geometry (such as the global NPC spaces and the Wasserstein spaces). We also discuss the connection between our concept of majorization and the subject of Schur convexity. Several applications are included.     

Ramanujan-Fourier series and the conjecture D of Hardy and Littlewood

We give a heuristic proof of a conjecture of Hardy and Littlewood concerning the density of prime pairs to which twin primes and Sophie Germain primes are special cases. The method uses the Ramanujan-Fourier series for a modified von Mangoldt function and the Wiener-Khintchine theorem for arithmetical functions. The failing of the heuristic proof is due to the lack of justification of interchange of certain limits. Experimental evidence using computer calculations is provided for the plausibility of the result. We have also shown that our argument can be extended to the m-tuple conjecture of Hardy and Littlewood.     

Sharp integral estimates for the fractional maximal function and interpolation

We give sharp estimates for the fractional maximal function in terms of Hausdorff capacity. At the same time we identify the real interpolation spaces between L ₁ and the Morrey space . The result can be viewed as an analogue of the Hardy–Littlewood maximal theorem for the fractional maximal function.     

On the necessity of the assumptions used to prove Hardy–Littlewood and Riesz rearrangement inequalities

We prove that supermodularity is a necessary condition for the generalized Hardy–Littlewood and Riesz rearrangement inequalities. We also show the necessity of the monotonicity of the kernels involved in the Riesz-type integral.     

Hardy–Sobolev inequalities in half-space and some semilinear elliptic equations with singular coefficients

We study some semilinear elliptic equations with singular coefficients which relate to some Hardy–Sobolev inequalities. We obtain some existence results for these equations and give a theorem for prescribing the Palais–Smale sequence for these equations. Moreover, we find some interesting connections between these equations and some semilinear elliptic equations in hyperbolic space. Using these connections, we obtain many new results for these equations.