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Maksim V. Kukushkin

Publications and source records attributed to Maksim V. Kukushkin.

15 recordsLinked to original sources
arXiv2026

Natural methods of unsupervised topological alignment

In this paper, we consider methods for the diagonal multi-omics integration of heterogeneous datasets. Several approaches to the nature of biological heterogeneity are analyzed and developed to comprehend more clearly the generated differences. Specifically, the extremal trace problems for the coupled Laplacian on sets homeomorphic to the Stiefel manifold embedded in the complex Euclidean space are investigated. The gradient ascent method for the maximization problem is elaborated in the classical terms of functional analysis, which is of significant interest in itself. On this basis, we introduce a novel characteristic of dataset heterogeneity by employing the norm of the difference between the maximum and minimum points.

math.FA↗
arXiv2026

Diagonal Multi-omics Integration of Heterogeneous Datasets

In this paper, we consider methods for the diagonal multi-omics integration of heterogeneous datasets. Several approaches to the nature of biological heterogeneity are analyzed and developed to comprehend more clearly the generated differences. Specifically, the extremal trace problems for the coupled Laplacian on sets homeomorphic to the Stiefel manifold embedded in the complex Euclidean space are investigated. The gradient ascent method for the maximization problem is elaborated in the classical terms of functional analysis, which is of significant interest in itself. On this basis, we introduce a novel characteristic of dataset heterogeneity by employing the norm of the difference between the maximum and minimum points.

stat.ML↗
arXiv2025

On the essential decreasing of the summation order in the Abel-Lidskii sense

In this paper, we consider a problem of decreasing the summation order in the Abel-Lidskii sense. The problem has a significant prehistory since 1962 created by such mathematicians as Lidskii V.B., Katsnelson V.E., Matsaev V.I., Agranovich M.S. As a main result, we will show that the summation order can be decreased from the values more than a convergence exponent, in accordance with the Lidskii V.B. result, to an arbitrary small positive number. Additionally, we construct a qualitative theory of summation in the Abel-Lidkii sense and produce a number of fundamental propositions representing the interest themselves.

math.FA↗
arXiv2024

Theory of sectorial operators and its application in Fractional calculus

In this monograph, we formulated the sufficient conditions of the Abel-Lidskii basis property for a sectorial operator. Having studied such an operator class, we strengthened the conditions regarding the semi-angle of the sector and weakened a great deal conditions regarding the involved parameters. Thus, we clarified the results by Lidskii V.B. devoted to the decomposition on the root vector system of the non-selfadjoint operator. We used a technique of the entire function theory and introduced the so-called Schatten-von Neumann class of the convergence exponent. Having considered strictly accretive operators satisfying special conditions formulated in terms of the norm and used a sequence of contours of the power type, we invented a peculiar method how to calculate a contour integral involved in the problem. Finally, we consider evolution equations in the abstract Hilbert space.

math.FA↗
arXiv2023

Schatten index of the operator via the real component of its inverse

In this paper we study spectral properties of non-selfadjoint operators with the discrete spectrum. The main challenge is to represent a complete description of belonging to the Schatten class through the properties of the Hermitian real component. The method of estimating the singular values is elaborated by virtue of the established asymptotic formulas. The latter fundamental result is advantageous since many theoretical statements based upon it, one of them is a concept on the root vectors series expansion which leads to a wide spectrum of applications in the theory of evolution equations. In this regard the evolution equations of fractional order with the operator in the term not containing the time variable are involved. The concrete well-known operators are considered and the advantage of the represented method is convexly shown.

math.FA↗
arXiv2023

Kipriyanov's Fractional Calculus Prehistory and Legacy

This paper is partly a historical survey of various approaches and methods in the fractional calculus, partly a description of the Kipriyanov extraordinary theory in comparison with the classical one. The significance and outstanding methods in constructing the independent Kipriyanov fractional calculus theory are convexly stressed, also we represent modern results involving the Kipriyanov operator and corresponding generalization under the semigroup theory point of view.

math.FA↗
arXiv2023

Schatten-von Neumann classes with more subtle asymptotics than one of the power type

In this paper we study non-selfadjoint operators using the methods of the spectral theory. The main challenge is to represent a complete description of an operator belonging to the Schatten-von Neumann class having used the order of the Hermitian real component. The latter fundamental result is advantageous since many theoretical statements based upon it and one of them is a concept on the root series expansion to say nothing on a wide spectrum of applications in the theory of evolution equations. In this regard the evolution equations of fractional order with the operator function in the term not containing the time variable are involved. Constructing the operator class satisfying the asymptotic more subtle than one of the power type, we show convexly the relevance of the obtained fundamental results.

math.FA↗
arXiv2023

Cauchy Problem for an abstract Evolution Equation of fractional order

In this paper, we define an operator function as a series of operators corresponding to the Taylor series representing the function of the complex variable. In previous papers, we considered the case when a function has a decomposition in the Laurent series with the infinite principal part and finite regular part. Our central challenge is to improve this result having considered as a regular part an entire function satisfying the special condition of the growth regularity. As an application we consider an opportunity to broaden the conditions imposed upon the second term not containing the time variable of the evolution equation in the abstract Hilbert space.

math.FA↗
arXiv2022

Abstract evolution equations with an operator function in the second term

In this paper, having introduced a convergence of a series on the root vectors in the Abel-Lidskii sense, we present a valuable application to the evolution equations. The main issue of the paper is an approach allowing us to principally broaden conditions imposed upon the right-hand side of the evolution equation in the abstract Hilbert space. In this way, we come to the definition of the function of an unbounded non-selfadjoint operator. Meanwhile, considering the main issue we involve an additional concept that is a generalization of the spectral theorem for a non-selfadjoint operator.

math.FA↗
arXiv2022

Natural lacunae method and Schatten-von Neumann classes of the convergence exponent

The first our aim is to clarify the results obtained by Lidskii devoted to the decomposition on the root vector system of the non-selfadjoint operator. We use a technique of the entire function theory and introduce a so-called Schatten-von Neumann class of the convergence exponent. Considering strictly accretive operators satisfying special conditions formulated in terms of the norm, we construct a sequence of contours of the power type on the contrary to the results by Lidskii, where a sequence of contours of the exponential type was used.

math.FA↗
arXiv2022

Evolution Equations in Hilbert Spaces via the Lacunae Method

In this paper we consider evolution equations in the abstract Hilbert space under the special conditions imposed on the operator at the right-hand side of the equation. We establish the method that allows us to formulate the existence and uniqueness theorem and find a solution in the form of a series on the root vectors of the right-hand side. As an application we consider fractional differential equations of various kinds. Such operators as the Riemann-Liouville fractional differential operator, the Riesz potential, the difference operator have been involved.

math.FA↗
arXiv2020

One more theorem on norm equivalence in the Lebesgue space

In this paper we consider a norm based on the infinitesimal generator of the shift semigroup in a direction. The relevance of such a focus is guaranteed by an abstract representation of a fractional integro-differential operator by means of a composition of the corresponding infinitesimal generator. The main result of the paper is a theorem establishing equivalence of norms in functional spaces. Even without mentioning the relevance of this result for the constructed theory, we claim it deserves to be considered itself.

math.FA↗
arXiv2020

Abstract Fractional Calculus for m-accretive Operators

In this paper we aim to construct an abstract model of a differential operator with a fractional integro-differential operator composition in final terms, where modeling is understood as an interpretation of concrete differential operators in terms of the infinitesimal generator of a corresponding semigroup. We study such operators as a Kipriyanov operator, Riesz potential, difference operator. Along with this, we consider transforms of m-accretive operators as a generalization, introduce an operator class $\mathfrak{G_α}$ and provide a description of its spectral properties.

math.FA↗
arXiv2020

On one application of the Zigmund-Marczinkevich theorem

In this paper we aim to generalize results obtained in the framework of fractional calculus by the way of reformulating them in terms of operator theory. In its own turn, the achieved generalization allows us to spread the obtained technique on practical problems that connected with various physical - chemical processes.

math.FA↗
arXiv2020

On Smoothness of the Abel Equation Solution in Terms of the Jacoby Series Coefficients

In this paper we continue the investigation of the Abel equation with the right part belonging to a Lebesgue weighted space. We have improved the previously known result - the uniqueness and existence theorem formulated in terms of the Jacoby series coefficients that gives us an opportunity to find and classify a solution due to an asymptotic of some relation containing the Jacoby coefficients of the right part. The new main results are in the following: The conditions imposed on the parameters, under which the Abel equation has a unique solution represented by the series, are formulated; The relationship between the values of the parameters and the solution smoothness is established. The independence between one of the parameters and the smoothness of the solution is proved.

math.FA↗