{"title":"Initial Value Problem for a Third-Order Nonlinear Integro-Differential Equation of Convolution Type","authors":"S. N. Askhabov","doi":"10.1134/s0012266124040086","DOIUrl":"https://doi.org/10.1134/s0012266124040086","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p> In this paper, we obtain two-sided a priori estimates for the solution of a homogeneous\u0000third-order Volterra integro-differential equation with a power-law nonlinearity and difference\u0000kernel. It is shown that the lower a priori estimate, which plays the role of a weight function when\u0000constructing a metric in the cone of the space of continuous functions, is sharp. Using these\u0000estimates, by the weighted metric method (an analog of A. Bielecki’s method), we prove a global\u0000theorem on the existence and uniqueness of a nontrivial solution of the initial value problem for\u0000this integro-differential equation in the class of nonnegative continuous functions on the positive\u0000half-line and on the method for finding this solution. It is shown that the solution can be found by\u0000the successive approximation method, and an estimate of the rate of convergence of the\u0000approximations to the exact solution is obtained. Examples are given to illustrate the results\u0000obtained.\u0000</p>","PeriodicalId":50580,"journal":{"name":"Differential Equations","volume":null,"pages":null},"PeriodicalIF":0.6,"publicationDate":"2024-07-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141867279","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"On the Eighty-Fifth Anniversary of Viktor Antonovich Sadovnichii","authors":"","doi":"10.1134/s0012266124040013","DOIUrl":"https://doi.org/10.1134/s0012266124040013","url":null,"abstract":"","PeriodicalId":50580,"journal":{"name":"Differential Equations","volume":null,"pages":null},"PeriodicalIF":0.6,"publicationDate":"2024-07-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141867341","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"On the Realization of Finite Essential Spectra of Oscillation Exponents of Two-Dimensional Differential Systems","authors":"A. Kh. Stash, N. A. Loboda","doi":"10.1134/s0012266124040062","DOIUrl":"https://doi.org/10.1134/s0012266124040062","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p> For any finite set of nonnegative numbers containing zero, we construct a two-dimensional\u0000linear homogeneous differential system (periodic if all elements of the given set are pairwise\u0000commensurate) in which the spectra of the oscillation exponents of signs, zeros, roots, and\u0000hyperroots coincide with this set, and all the values of these exponents are essential.\u0000</p>","PeriodicalId":50580,"journal":{"name":"Differential Equations","volume":null,"pages":null},"PeriodicalIF":0.6,"publicationDate":"2024-07-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141867281","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Singularly Perturbed Optimal Tracking Problem","authors":"V. A. Sobolev","doi":"10.1134/s0012266124040116","DOIUrl":"https://doi.org/10.1134/s0012266124040116","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p> We consider a singularly perturbed optimal tracking problem with a given reference path\u0000in the case of incomplete information about the state vector in the presence of exogenous\u0000disturbances. To analyze the differential equations that arise when solving this problem, we use\u0000the decomposition method, which is based on the technique of integral manifolds of fast and slow\u0000motions.\u0000</p>","PeriodicalId":50580,"journal":{"name":"Differential Equations","volume":null,"pages":null},"PeriodicalIF":0.6,"publicationDate":"2024-07-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141873003","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Christoffel–Darboux Formula for Polynomial Eigenfunctions of Second-Order Linear Differential Equations","authors":"V. E. Kruglov","doi":"10.1134/s0012266124040037","DOIUrl":"https://doi.org/10.1134/s0012266124040037","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p> Using recurrence relations between any three consecutive polynomial eigenfunctions of\u0000second-order linear differential equations, the Christoffel–Darboux formulas are derived for the\u0000system of polynomial eigenfunctions of these equations.\u0000</p>","PeriodicalId":50580,"journal":{"name":"Differential Equations","volume":null,"pages":null},"PeriodicalIF":0.6,"publicationDate":"2024-07-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141867276","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Stabilization of a Switched System with Commensurate Delays under Slow Switchings","authors":"A. V. Il’in, A. S. Fursov","doi":"10.1134/s0012266124040104","DOIUrl":"https://doi.org/10.1134/s0012266124040104","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p> An approach is proposed to constructing a digital controller that stabilizes a\u0000continuous-time switched linear system with commensurate delays in control under slow\u0000switchings. The approach to stabilization consistently includes the construction of a switched\u0000continuous–discrete-time closed-loop system with a digital controller, the transition to its\u0000discrete-time model, represented in the form of a switched system with modes of different orders,\u0000simultaneous stabilization of the subsystems of the resulting discrete-time model, and calculation\u0000of a delay time that ensures the stability of the original switched system closed by the controller\u0000found.\u0000</p>","PeriodicalId":50580,"journal":{"name":"Differential Equations","volume":null,"pages":null},"PeriodicalIF":0.6,"publicationDate":"2024-07-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141873062","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Asymptotically Stable Solutions with Boundary and Internal Layers in Direct and Inverse Problems for a Singularly Perturbed Heat Equation with Nonlinear Thermal Diffusion","authors":"M. A. Davydova, G. D. Rublev","doi":"10.1134/s0012266124040025","DOIUrl":"https://doi.org/10.1134/s0012266124040025","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p> This paper proposes a new approach to the study of direct and inverse problems for a\u0000singularly perturbed heat equation with nonlinear temperature-dependent diffusion, based on the\u0000further development and use of asymptotic analysis methods in the nonlinear singularly perturbed\u0000reaction–diffusion–advection problems. The essence of the approach is presented using the\u0000example of one class of one-dimensional stationary problems with nonlinear boundary conditions,\u0000for which the case of applicability of asymptotic analysis is singled out. Sufficient conditions for\u0000the existence of classical solutions of the boundary layer type and the type of contrast structures\u0000are formulated, asymptotic approximations of an arbitrary order of accuracy to such solutions are\u0000constructed, algorithms for constructing formal asymptotics are substantiated, and the Lyapunov\u0000asymptotic stability of stationary solutions with boundary and internal layers as solutions of the\u0000corresponding parabolic problems is investigated. A class of nonlinear problems that take into\u0000account lateral heat exchange with the environment according to Newton’s law is considered.\u0000A theorem on the existence and uniqueness of a classical solution with boundary layers in\u0000problems of this type is proved. As applications of this research, methods for solving specific\u0000direct and inverse problems of nonlinear heat transfer related to increasing the operating efficiency\u0000of rectilinear heating elements in the smelting furnaces (heat exchangers) are presented, which\u0000include the calculation of thermal fields in the heating elements and a method for reconstructing\u0000thermal diffusion and heat transfer coefficients based on modeling data.\u0000</p>","PeriodicalId":50580,"journal":{"name":"Differential Equations","volume":null,"pages":null},"PeriodicalIF":0.6,"publicationDate":"2024-07-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141867342","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"An Inverse Problem for the Wave Equation with Two Nonlinear Terms","authors":"V. G. Romanov","doi":"10.1134/s0012266124040074","DOIUrl":"https://doi.org/10.1134/s0012266124040074","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p> An inverse problem for a second-order hyperbolic equation containing two nonlinear terms\u0000is studied. The problem is to reconstruct the coefficients of the nonlinearities. The Cauchy\u0000problem with a point source located at a point <span>(mathbf {y})</span> is\u0000considered. This point is a parameter of the problem and successively runs over a spherical surface\u0000<span>(S )</span>. It is assumed that the desired coefficients are\u0000nonzero only in a domain lying inside <span>(S)</span>. The trace of the\u0000solution of the Cauchy problem on <span>(S)</span> is specified for all\u0000possible values of <span>( mathbf {y})</span> and for times close to the arrival of\u0000the wave from the source to the points on the surface <span>(S )</span>; this allows reducing the inverse problem under\u0000consideration to two successively solved problems of integral geometry. Solution stability estimates\u0000are found for these two problems.\u0000</p>","PeriodicalId":50580,"journal":{"name":"Differential Equations","volume":null,"pages":null},"PeriodicalIF":0.6,"publicationDate":"2024-07-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141873002","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"On the Existence of Nonlinearizable Solutions of a Nonclassical Two-Parameter Nonlinear Boundary Value Problem","authors":"V. Yu. Martynova","doi":"10.1134/s0012266124040049","DOIUrl":"https://doi.org/10.1134/s0012266124040049","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p> A nonlinear eigenvalue problem for a system of three equations with boundary conditions\u0000of the first kind, describing the propagation of electromagnetic waves in a plane nonlinear\u0000waveguide, is considered. This is a two-parameter problem with one spectral parameter and a\u0000second parameter arising from an additional condition. This condition connects the integration\u0000constants that arise when finding the first integrals of the system. The existence of nonlinearizable\u0000solutions of the problem is proved.\u0000</p>","PeriodicalId":50580,"journal":{"name":"Differential Equations","volume":null,"pages":null},"PeriodicalIF":0.6,"publicationDate":"2024-07-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141867277","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Optimization Inverse Spectral Problem for the One-Dimensional Schrödinger Operator on the Entire Real Line","authors":"V. A. Sadovnichii, Ya. T. Sultanaev, N. F. Valeev","doi":"10.1134/s0012266124040050","DOIUrl":"https://doi.org/10.1134/s0012266124040050","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p> We study the statement of the optimization inverse spectral problem with incomplete\u0000spectral data for the one-dimensional Schrödinger operator on the entire axis: for a given\u0000potential <span>(q_0 )</span>, find the closest function <span>(hat {q} )</span> such that the first <span>(m )</span> eigenvalues of the Schrödinger operator\u0000with potential <span>(hat {q})</span> coincide with given values <span>(lambda _k^*in mathbb {R} )</span>, <span>(k={1,dots ,m})</span>.\u0000</p>","PeriodicalId":50580,"journal":{"name":"Differential Equations","volume":null,"pages":null},"PeriodicalIF":0.6,"publicationDate":"2024-07-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141867278","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}