Integro-differential Operators Research Articles

Singular solutions for space-time fractional equations in a bounded domain

This paper is devoted to describing a linear diffusion problem involving fractional-in-time derivatives and self-adjoint integro-differential space operators posed in bounded domains. One main concern of our paper is to deal with singular boundary data which are typical of fractional diffusion operators in space, and the other one is the consideration of the fractional-in-time Caputo and Riemann–Liouville derivatives in a unified way. We first construct classical solutions of our problems using the spectral theory and discussing the corresponding fractional-in-time ordinary differential equations. We take advantage of the duality between these fractional-in-time derivatives to introduce the notion of weak-dual solution for weighted-integrable data. As the main result of the paper, we prove the well-posedness of the initial and boundary-value problems in this sense.

The fundamental theorem of calculus in differential rings

In this paper, we study the consequences of the fundamental theorem of calculus from an algebraic point of view. For functions with singularities, this leads to a generalized notion of evaluation. We investigate properties of such integro-differential rings and discuss many examples. We also construct corresponding integro-differential operators and provide normal forms via rewrite rules. They are then used to derive several identities and properties in a purely algebraic way, generalizing well-known results from analysis. In identities like shuffle relations for nested integrals and the Taylor formula, additional terms are obtained that take singularities into account. Another focus lies on treating basics of linear ODEs in this framework of integro-differential operators. These operators can have matrix coefficients, which allow to treat systems of arbitrary size in a unified way. In the appendix, using tensor reduction systems, we give the technical details of normal forms and prove them for operators including other functionals besides evaluation.

Three-dimensional spontaneous flow transition in a homeotropic active nematic

Active nematics are driven, non-equilibrium systems relevant to biological processes including tissue mechanics and morphogenesis, and to active metamaterials in general. We study the three-dimensional spontaneous flow transition of an active nematic in an infinite slab geometry using a combination of numerics and analytics. We show that it is determined by the interplay of two eigenmodes – called S- and D-mode – that are unstable at the same activity threshold and spontaneously breaks both rotational symmetry and chiral symmetry. The onset of the unstable modes is described by a non-Hermitian integro-differential operator, which we determine their exponential growth rates from using perturbation theory. The S-mode is the fastest growing. After it reaches a finite amplitude, the growth of the D-mode is anisotropic, being promoted perpendicular to the S-mode and suppressed parallel to it, forming a steady state with a full three-dimensional director field and a well-defined chirality. Lastly, we derive a model of the leading-order time evolution of the system close to the activity threshold.

The infinite-order integro-differential operator related to the Lebedev–Skalskaya transform

The infinite-order integro-differential operator related to the Lebedev–Skalskaya transform

On $$L_{p}-$$ Theory for Integro-Differential Operators with Spatially Dependent Coefficients

On $$L_{p}-$$ Theory for Integro-Differential Operators with Spatially Dependent Coefficients

On the reconstruction of an integro-differential Dirac operator with parameter-dependent nonlocal integral boundary conditions from the nodal data

On the reconstruction of an integro-differential Dirac operator with parameter-dependent nonlocal integral boundary conditions from the nodal data

On a family of fully nonlinear integrodifferential operators : from fractional Laplacian to nonlocal Monge–Ampère

On a family of fully nonlinear integrodifferential operators : from fractional Laplacian to nonlocal Monge–Ampère

Obstacle Problems for Integro-Differential Operators with Partially Vanishing Kernels

Obstacle Problems for Integro-Differential Operators with Partially Vanishing Kernels

Rational Factorization of Hamiltonian Flows in the Space Dual to the Lie Algebra of Fractional Integrodifferential Operators and Benney-Type Integrable Hydrodynamic Systems

Rational Factorization of Hamiltonian Flows in the Space Dual to the Lie Algebra of Fractional Integrodifferential Operators and Benney-Type Integrable Hydrodynamic Systems

Robust nonlocal trace spaces and Neumann problems

We prove trace and extension results for fractional Sobolev spaces of order s∈(0,1). These spaces are used in the study of nonlocal Dirichlet and Neumann problems on bounded domains. The results are robust in the sense that the continuity of the trace and extension operators is uniform as s approaches 1 and our trace spaces converge to H1/2(∂Ω). We apply these results in order to study the convergence of solutions of nonlocal Neumann problems as the integro-differential operators localize to a symmetric, second order operator in divergence form.

Convexity Properties for Integro‑Differential Operators Proposed by Hurwitz-Lerch Zeta Type Functions

In this paper, new integro-differential operators are introduced that defined by Salagean’s differential operator. The major object of the present study is to investigate convexity properties on new geometric subclasses included these new operators.

Mathematical Model of the Unbalanced Monopole Feed. Part 3. Gain

An integro-differential operator is specified that determines the longitudinal component of the electric field strength on the surface of the emitter conductor of an Unbalanced Monopole with Shunt Feed, created by the Base Current (BC). Analytical expressions are obtained that determine the parameters of an equivalent eight pole, which is the internal resistance of equivalent BC generators. The influence of the length of the counterweight conductors and the upper load of the high-voltage transformer on the efficiency and gain was studied.

Concentration-compactness type principle for systems with critical terms in [formula omitted

In this paper, we obtain some important variants of the Lions and Chabrowski Concentration-compactness principle, for nonlinear systems in the context of fractional Sobolev spaces with variable exponents. As an application of the results, we show the existence and asymptotic behaviour of nontrivial solutions for elliptic systems involving a new class of general nonlocal integrodifferential operators with variable exponents and critical growth conditions in RN.

Time-fractional Davey–Stewartson equation: Lie point symmetries, similarity reductions, conservation laws and traveling wave solutions

As a celebrated nonlinear water wave equation, the Davey–Stewartson equation is widely studied by researchers, especially in the field of mathematical physics. On the basis of the Riemann–Liouville fractional derivative, the time-fractional Davey–Stewartson equation is investigated in this paper. By application of the Lie symmetry analysis approach, the Lie point symmetries and symmetry groups are obtained. At the same time, the similarity reductions are derived. Furthermore, the equation is converted to a system of fractional partial differential equations and a system of fractional ordinary differential equations in the sense of Riemann–Liouville fractional derivative. By virtue of the symmetry corresponding to the scalar transformation, the equation is converted to a system of fractional ordinary differential equations in the sense of Erdélyi–Kober fractional integro-differential operators. By using Noether’s theorem and Ibragimov’s new conservation theorem, the conserved vectors and the conservation laws are derived. Finally, the traveling wave solutions are achieved and plotted.

Time-fractional Caputo derivative versus other integrodifferential operators in generalized Fokker-Planck and generalized Langevin equations.

Fractional diffusion and Fokker-Planck equationsare widely used tools to describe anomalous diffusion in a large variety of complex systems. The equivalent formulations in terms of Caputo or Riemann-Liouville fractional derivatives can be derived as continuum limits of continuous-time random walks and are associated with the Mittag-Leffler relaxation of Fourier modes, interpolating between a short-time stretched exponential and a long-time inverse power-law scaling. More recently, a number of other integrodifferential operators have been proposed, including the Caputo-Fabrizio and Atangana-Baleanu forms. Moreover, the conformable derivative has been introduced. We study here the dynamics of the associated generalized Fokker-Planck equationsfrom the perspective of the moments, the time-averaged mean-squared displacements, and the autocovariance functions. We also study generalized Langevin equationsbased on these generalized operators. The differences between the Fokker-Planck and Langevin equations with different integrodifferential operators are discussed and compared with the dynamic behavior of established models of scaled Brownian motion and fractional Brownian motion. We demonstrate that the integrodifferential operators with exponential and Mittag-Leffler kernels are not suitable to be introduced to Fokker-Planck and Langevin equationsfor the physically relevant diffusion scenarios discussed in our paper. The conformable and Caputo Langevin equationsare unveiled to share similar properties with scaled and fractional Brownian motion, respectively.

The fractional integrodifferential operator and its univalence and boundedness features according to Pre-Schwarzian derivative structure

Complex-valued regular functions that are normalized in the open unit disk are vastly studied. The current study introduces a new fractional integrodifferential (non-linear) operator. Based on the pre-Schwarzian derivative, certain appropriate stipulations on the parameters included in this constructed operator to be univalent and bounded are investigated and determined.

Hopf type lemmas for subsolutions of integro-differential equations

In the paper we prove a lower bound for subsolutions of the integro-differential equation: −Au+cu=0 in a domain D. It states that there exists a Borel function ψ, strictly positive on D, depending only on the coefficients of the operator A, c and D such that for any subsolution u(⋅), that satisfies supy∈DSu(y)≥0, one can find a constant a>0 (that in general depends on u), for which supy∈DSu(y)−u(x)≥aψ(x), x∈D. The bound is valid for a wide class of Lévy type integro-differential operators A, non-negative, bounded and measurable function c and a quite general domain D⊂Rd. Here DS is a certain set containing the closure of D and determined by the support of the Levy jump measure associated with A. In some cases a non-negative eigenfunction corresponding to the operator in D can be admitted as the function ψ. In particular, this occurs when the transition probability semigroup associated with A is ultracontractive. The main assumptions made about A are: there exists a strong Markov solution to the martingale problem associated with the operator and its resolvent satisfies some minorization condition. This type of a result we call the generalized Hopf lemma.

On Some Boundary Value Problems with a Shift for a Mixed Type Equation

Важным этапом в становлении теории краевых задач стали предложенные А.М. Нахушевым в 1969 году нелокальные задачи нового типа, впоследствии названные у нас краевыми задачами со смещением, а за рубежом — задачами (проблемами) Нахушева. Они являются обобщением задачи Трикоми, а так же содержат широкий класс корректных самосопряженных задач. Эти задачи сразу вызвали большой интерес многих авторов. За последние годы исследования задач со смещением для уравнений смешанного типа ведутся особенно интенсивно. Но в этих работах краевые условия, как правило, содержат классические операторы, в то время как нелокальным краевым задачам, содержащим операторы более сложной структуры и операторы дробного интегро-дифференцирования. Настоящая статья посвящена исследованию вопроса однозначной разрешимости краевых задач со смещением для уравнения смешанного эллиптико-гиперболического типа. Сформулированы корректные краевые задачи со смещением для уравнения смешанного типа. В данной работе исследованы вопросы однозначной разрешимости задач со смешением для уравнения смешанного эллиптико-гиперболического типа в смешанной области Ω, ограниченной в полуплоскости y>0 гладкой кривой Жордана, а в полуплоскости y<0 характеристиками уравнения (1). При ограничениях неравенственного типа на известные функции и различных порядках операторов дробного дифференцирования в краевом условии доказаны теоремы единственности. Существование решения задач доказывается путем редукции задач к уравнениям Фредгольма второго рода, безусловная разрешимость которых следует из единственности решения задач. An important stage in the development of the theory of boundary value problems was the proposed by A.M. Nakhushev in 1969, non-local problems of a new type, which were later called in our country boundary value problems with a shift, and abroad – Nakhushev problems (problems). They are a generalization of the Tricomi problem, and also contain a wide class of well-posed self-adjoint problems. These problems immediately aroused great interest of many authors. In recent years, studies of problems with a shift for equations of mixed type have been carried out especially intensively. But in these works, the boundary conditions, as a rule, contain classical operators, while non-local boundary value problems contain operators of a more complex structure and operators of fractional integro-differentiation. In this paper, we study the unique solvability of problems with mixing for an equation of mixed elliptic-hyperbolic type. Under constraints of unequal type on known functions and different orders of fractional differentiation operators in the boundary condition, uniqueness theorems are proved. The existence of a solution to the problems is proved by reducing the problems to Fredholm equations of the second kind, the unconditional solvability of which follows from the uniqueness of the solution to the problems.

On the Adjoint Problem in a Domain with Deviation Out from the Characteristic for the Mixed Parabolic-Hyperbolic Equation with the Fractional Order Operator

В настоящей статье доказана классическая, сильная разрешимость и вольтерровость сопряженной задачи c отходом от характеристики для уравнения смешанного параболо-гиперболического типа с оператором дробного порядка в смысле Герасимова-Капуто. Целью исследования является решение сопряженной задачи для уравнения смешанного параболо-гиперболического типа дробного порядка. Учитывая, свойств операторов дробного порядка найдены сопряженный оператор и применены постановки сопряженной задачи. Для исследования поставленной задачи в параболической частью смешанной области решается первой краевой задачи для уравнения параболического типа дробного порядка в смысле Герасимова-Капуто. Используя, свойств функции Райта получено функциональное соотношение на линии перехода. Точно также решая, задачи Коши гиперболической частью смешанной области находим функциональное соотношение. Следовательно, поставленная задача эквивалентным образом сводится к интегральному уравнению Вольтерра второго рода со слабой особенностью. Согласно теории интегральных уравнений Вольтерра второго рода доказывается однозначной разрешимость полученного уравнения. Кроме того, используя методы операторов интегро — дифференцирования дробного порядка, теории специальных функций, априорных оценок, теория интегральных уравнений доказываются теоремы единственности, существования и вольтерровость сопряженной задачи в области с отходом от характеристики для уравнения смешанного типа дробного порядка. Полученные результаты новые и отличаются от результатов М.А. Садыбекова и А.С. Бердышева. In this article, it was proved the classical, strong solvability and Volterra property of the adjoint problem with departure from the characteristic for an equation of mixed parabolic-hyperbolic type with a fractional order operator in the sense of Gerasimov-Caputo. The aim of the research is to solve the conjugate problem for the equation of a mixed parabolic-hyperbolic type of fractional order. Taking into account the properties of fractional order operators, the adjoint operator is found and the statements of the adjoint problem are applied. To study the formulated problem in the parabolic part of the mixed domain, the first boundary value problem for a parabolic type equation of fractional order in the sense of Gerasimov-Caputo is solved. Using the properties of the Wright function, a functional relation is obtained on the transition line. In the same way, solving the Cauchy problem with the hyperbolic part of the mixed domain, we find a functional relation. Consequently, the problem posed reduces in an equivalent way to a Volterra integral equation of the second kind with a weak singularity. According to the theory of Volterra integral equations of the second kind, the unique solvability of the resulting equation is proved. In addition, using the methods of integro-differentiation operators of fractional order, the theory of special functions, a priori estimates, the theory of integral equations, uniqueness, existence and Volterra theorems for the adjoint problem in a domain with deviation out of the characteristic for a mixed-type equation of fractional order are proved. The results obtained are new and differ from the results of M. A. Sadybekov and A. S. Berdyshev.

All linear fractional derivatives with power functions’ convolution kernel and interpolation properties

Our attempt is an axiomatic approach to find all classes of possible definitions for fractional derivatives with three axioms. In this paper, we consider a special case of linear integro-differential operators with power functions’ convolution kernel a(α)(t−s)b(α) of order α∈(0,1). We determine analytic functions a(α) and b(α) such that when α→0+, the corresponding operator becomes identity operator, and when α→1− the corresponding operator becomes derivative operator. Then, a sequential operator is used to extend the fractional operator to a higher order. Some properties of the sequential operator in this regard also are studied. The singularity properties, Laplace transform and inverse of the new class of fractional derivatives are investigated. Several examples are provided to confirm theoretical achievements. Finally, the solution of the relaxation equation with diverse fractional derivatives is obtained and compared.