On some properties of fractional dyadic derivative and integral

Summary For the fractional dyadic derivative and integral, the following analogues of two theorems of Lebesgue are proved: the theorem on differentiation of the indefinite Lebesgue integral of an integrable function at its Lebesgue points, and the theorem on reconstruction of an absolutely continuous function by means of its derivative. Dyadic fractional analogues of the formula of integration by parts are also obtained. In addition, some theorems are proved on dyadic fractional differentiation and integration of a Lebesgue integral depending on a parameter. Most of the results are new even for dyadic derivatives and integrals of natural order.     

On Denjoy type extensions of the Pettis integral

In this paper two Denjoy type extensions of the Pettis integral are defined and studied. These integrals are shown to extend the Pettis integral in a natural way analogous to that in which the Denjoy integrals extend the Lebesgue integral for real-valued functions. The connection between some Denjoy type extensions of the Pettis integral is examined.     

The Lebesgue summability of trigonometric integrals

Motivated by the notion of Lebesgue summability of trigonometric series, we define the Lebesgue summability of trigonometric integrals in terms of the symmetric differentiability of the sum of the formally integrated trigonometric integral in question. We extend two theorems of Zygmund from trigonometric series to integrals, and one of them even in a more general form.     

On existence of integrable solutions of a functional integral equation under Carathéodory conditions

We study the solvability of a functional integral equation in the space of Lebesgue integrable functions on an unbounded interval. Using the conjunction of the technique of measures of weak noncompactness with the classical Schauder fixed point principle we show that the equation in question is solvable in the mentioned function space. Our existence result is obtained under the assumption that functions involved in the investigated functional integral equation satisfy Carathéodory conditions. Moreover, that result generalizes several ones obtained earlier in many research papers and monographs.     

Generalized Lebesgue integral

A new definition of integral-like functionals exploiting the ideas of the Lebesgue integral construction and extending the idea of pan-integrals is given. Some convergence theorems for sequence of measurable functions are discussed. As a result, a theoretical basis for applications of the generalized Lebesgue integral is provided. Several types of integrals known from the literature are shown to be special cases of generalized Lebesgue integral.     

Familiarizing Students with Definition of Lebesgue Integral: Examples of Calculation Directly from Its Definition Using Mathematica

We present in this paper several examples of Lebesgue integral calculated directly from its definitions using Mathematica. Calculation of Riemann integrals directly from its definitions for some elementary functions is standard in higher mathematics education. But it is difficult to find analogical examples for Lebesgue integral in the available literature. The paper contains Mathematica codes which we prepared to calculate symbolically Lebesgue sums and limits of sums. We also visualize the graphs of simple functions used for approximation of the integrals. We also show how to calculate the needed sums and limits by hand (without CAS). We compare our calculations in Mathematica with calculations in some other CAS programs such as wxMaxima, MuPAD and Sage for the same integrals.     

Integral Representations and Transforms of N-Functions. I

The author has proposed a new approach to extrapolation of operators from the scale of Lebesgue spaces to the Orlicz spaces beyond this scale. In this article comprising two parts we develop some mathematical method that enables us to prove extrapolation theorems for arbitrary behavior of an operator in the Lebesgue scale (i.e., in the case when the norm of the operator is an arbitrary function of p) and also in the case when the basic scale is an interval of the Lebesgue scale with exponents separated from 1 or +∞. In this event, we face ill-posed problems of inversion of the classical Mellin and Laplace type integral transforms over nonanalytic functions in terms of their asymptotic behavior on the real axis and also the question about the properties of convolution type integral transforms on classes of N-functions. In the first part of the article we study integral representations for N-functions by expansions in power functions with a positive weight and the behavior of convolution type integral transforms on classes of N-functions.     

The widest continuous integral

An approach to a definition of an integral, which differs from definitions of Lebesgue and Henstock-Kurzweil integrals, is considered. We use trigonometrical polynomials instead of simple functions. Let V be the space of all complex trigonometrical polynomials without the free term. The definition of a continuous integral on the space V is introduced. All continuous integrals are described in terms of norms on V. The existence of the widest continuous integral is proved, the explicit form of its norm is obtained and it is proved that this norm is equivalent to the Alexiewicz norm. It is shown that the widest continuous integral is wider than the Lebesgue integral. An analog of the fundamental theorem of calculus for the widest continuous integral is given.     

Infinite-horizon optimal controls for problems governed by a volterra integral equation with state-and-control-dependent discount factor

In this work, we concern ourselves with the existence of optimal solutions to optimal control problems defined on an unbounded time interval with states governed by a nonlinear Volterra integral equation. These results extend both the work of Baum and others in infinite-horizon control of ordinary differential equations as well as the work of Angell concerning integral equations. In addition, we incorporate into the objective functional (described by an improper integral) a discount factor which reflects a hereditary dependence on both state and control. In this manner, we are able to generalize the recent results of Becker, Boyd, and Sung in which they establish an existence theorem in the calculus of variations with objective functionals of the so-called recursive type. Our results are obtained through the use of appropriate lower-closure theorems and compactness conditions. Examples are presented in which the applicability of our results is demonstrated.This research was supported by the National Science Foundation, Grant No. DMS-87-00706.     

Singular integrals and commutators on homogeneous groups

Let G be a homogeneous group. In this paper, the authors establish several general theorems for the boundedness of sublinear operators and commutators generated by linear operators and BMO(G)functions on the weighted Lebesgue space on G. The conditions of these theorems are satisfied by many important operators in analysis and these operators satisfy only some weak conditions on the size of operators and are known to be bounded in the unweighted case. Some of these theorems are best possible even when G is the Euclidean space. The authors also give some applications of their theorems to the boundedness on weighted spaces of rough singular integrals, oscillatory integrals, parabolic singular integrals, their commutators and the maximal operators associated with them.     

Convergence Theorems for the Henstock—Kurzweil—Pettis Integral

We prove some convergence theorems for the Henstock-Kurzweil- Pettis and Denjoy-Pettis integrals. Since these integrals are more general than some “classical” non-absolute integrals and than the Pettis integral, we generalize well-known convergence theorems for both types of the mentioned integrals.     

Multilinear Calderón Zygmund operators on variable exponent Morrey spaces over domains

The boundedness of multilinear singular integrals of Calderón-Zygmund type on product of variable exponent Lebesgue spaces over both bounded and unbounded domains are obtained. Further more, the boundedness for this type multilinear operators on product of variable exponent Morrey spaces over domains is shown in the paper.     

Bilinear oscillatory integrals and boundedness for new bilinear multipliers

We consider bilinear oscillatory integrals, i.e. pseudo-product operators whose symbol involves an oscillating factor. Lebesgue space inequalities are established, which give decay as the oscillation becomes stronger; this extends the well-known linear theory of oscillatory integral in some directions. The proof relies on a combination of time-frequency analysis of Coifman-Meyer type with stationary and non-stationary phase estimates. As a consequence of this analysis, we obtain Lebesgue estimates for new bilinear multipliers defined by non-smooth symbols.     

Special Boundary Integral Equations for Approximate Solution of Potential Problems in Three-dimensional Regions with Slender Cavities of Circular Cross-section

A special boundary integral method is developed for solvingpotential problems in a general three-dimensional region withslender internal cavities of circular cross-section. The solutionon the boundary of each cavity is assumed to be axisymmetricso that the surface integrals on a cavity boundary may be reducedto contour integrals along the centre line of the cavity. Specialintegral equations are introduced to determine the solutionalong each cavity. Although the contour integrals in these newequations are never singular, they have a nearly singular characterwhich gives them computational advantages similar to traditionalboundary integral equations with out the danger of ill-conditioningcaused by the strongly contrasting length scales introducedby the slender cavities. For the special case of parallel toroidalcavities, the method gives results with accuracy comparableto previous perturbation methods. The numerical characteristicsof the new integral equations are explored by solving the problemsof two perpendicular, interlocking tori and two perpendicular,finite cylindrical cavities, both in unbounded regions. Theequations exhibit excellent numerical characteristics over abroad range of parameters.     

Measures of Simultaneous Approximation for Quasi-Periods of Abelian Varieties

We examine various extensions of a series of theorems proved by Chudnovsky in the 1980s on the algebraic independence (transcendence degree 2) of certain quantities involving integrals of the first and second kind on elliptic curves; these extensions include generalizations to abelian varieties of arbitrary dimensions, quantitative refinements in terms of measures of simultaneous approximation, as well as some attempt at unifying the aforementioned theorems. In the process we develop tools that might prove useful in other contexts, revolving around explicit “algebraic” theta functions on the one hand, and Eisenstein's theorem and G-functions on the other hand.     

On Elliptic Homogeneous Differential Operators in Grand Spaces

We give an application of so-called grand Lebesgue and grand Sobolev spaces, intensively studied during last decades, to partial differential equations. In the case of unbounded domains such spaces are defined using so-called grandizers. Under some natural assumptions on the choice of grandizers, we prove the existence, in some grand Sobolev space, of a solution to the equation Pm(D)u(x) = f(x), x ∈ ℝn, m < n, with the right-hand side in the corresponding grand Lebesgue space, where Pm(D) is an arbitrary elliptic homogeneous in the general case we improve some known facts for the fundamental solution of the operator Pm(D): we construct it in the closed form either in terms of spherical hypersingular integrals or in terms of some averages along plane sections of the unit sphere.     

Asymptotic behavior and attractors for reaction diffusion equations in unbounded domains

In this paper we give general and flexible conditions for a reaction diffusion equation to be dissipative in an unbounded domain. The functional setting is based on standard Lebesgue and Sobolev–Lebesgue spaces. We show how the reaction and diffusion mechanisms have to work together to obtain the asymptotic compactness of solutions and therefore the existence of the compact attractor. In particular cases, our results allow us to improve some previous known results.