Direct and inverse problems for equations with fractional derivatives are arising in various fields of science and technology. The conditions for classical solvability of the Cauchy and boundary-value prob-lems for diffusion-wave equations with fractional derivatives are known. Estimates of components of the Green's vector-function of the Cauchy problem for such equations are known. We study the inverse problem of determining the space-dependent component of the right-hand side of the equation with a time fractional derivative and known functions from Schwartz-type space of smooth rapidly decreasing functions or with values in them. We also consider such a problem in the case of data from some wider space of smooth, decreasing to zero at infinity functions or with values in them. We find sufficient conditions for unique solvability of the inverse problem under the time-integral additional condition [frac{1}{T}int_{0}^{T}u(x,t)eta_1(t)dt=Phi_1(x), ;;;xin Bbb R^n] where $u$ is the unknown solution of the Cauchy problem, $eta_1$ and $Phi_1$ are the given functions. Using the method of the Green's vector function, we reduce the problem to solvability of an integrodifferential equation in a certain class of smooth, decreasing to zero at infinity functions. We prove its unique solvability. There are various methods for the approximate solution of direct and inverse problems for equations with fractional derivatives, mainly for the one-dimensional spatial case. It follows from our results the method of constructing an approximate solution of the inverse problem in the multidimensional spatial case. It is based on the use of known methods of constructing the numerical solutions of integrodifferential equations. The application of the Fourier transform by spatial variables is effective for constructing a numerical solution of the obtained integrodifferential equation, since the Fourier transform of the components of the Green's vector function can be explicitly written.
{"title":"REGULAR SOLUTION OF THE INVERSE PROBLEM WITH INTEGRAL CONDITION FOR A TIME-FRACTIONAL EQUATION","authors":"H. Lopushanska, A. Lopushansky","doi":"10.31861/bmj2020.02.09","DOIUrl":"https://doi.org/10.31861/bmj2020.02.09","url":null,"abstract":"Direct and inverse problems for equations with fractional derivatives are arising in various fields of science and technology. The conditions for classical solvability of the Cauchy and boundary-value prob-lems for diffusion-wave equations with fractional derivatives are known. Estimates of components of the Green's vector-function of the Cauchy problem for such equations are known.\u0000\u0000We study the inverse problem of determining the space-dependent component of the right-hand side of the equation with a time fractional derivative and known functions from Schwartz-type space of smooth rapidly decreasing functions or with values in them. We also consider such a problem in the case of data from some wider space of smooth, decreasing to zero at infinity functions or with values in them.\u0000\u0000We find sufficient conditions for unique solvability of the inverse problem under the time-integral additional condition\u0000[frac{1}{T}int_{0}^{T}u(x,t)eta_1(t)dt=Phi_1(x), ;;;xin Bbb R^n]\u0000where $u$ is the unknown solution of the Cauchy problem, $eta_1$ and $Phi_1$ are the given functions.\u0000\u0000Using the method of the Green's vector function,\u0000we reduce the problem to solvability of an integrodifferential equation in a certain class of smooth, decreasing to zero at infinity functions. We prove its unique solvability.\u0000\u0000There are various methods for the approximate solution of direct and inverse problems for equations with fractional derivatives, mainly for the one-dimensional spatial case. It follows from our results the method of constructing an approximate solution of the inverse problem in the multidimensional spatial case. It is based on the use of known methods of constructing the numerical solutions of integrodifferential equations. The application of the Fourier transform by spatial variables is effective for constructing a numerical solution of the obtained integrodifferential equation, since the Fourier transform of the components of the Green's vector function can be explicitly written.","PeriodicalId":196726,"journal":{"name":"Bukovinian Mathematical Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128618448","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Optimal control in a nonlocal boundary value problem with integral conditions for parabolic equation with degeneration","authors":"I. Pukal’skii, B. Yashan","doi":"10.31861/bmj2019.01.082","DOIUrl":"https://doi.org/10.31861/bmj2019.01.082","url":null,"abstract":"","PeriodicalId":196726,"journal":{"name":"Bukovinian Mathematical Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116382797","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The problems for Eidelman type equations and systems of equations are considered in this paper. They were the large part of scientific interests for Prof. Ivasyshen S.D. The results of investigations of Cauchy problem, initial-boundary and the inverse problems for this type of equations in bounded or unbounded domains are given. The results are represented as the estimates of the solutions, the integral representations of solutions, theorems of the existence, uniqueness and stability of solutions.
{"title":"ON PROBLEMS FOR EIDELMAN TYPE EQUATIONS AND SYSTEM OF EQUATIONS","authors":"N. Protsakh, H. Ivasiuk, T. Fratavchan","doi":"10.31861/bmj2022.02.17","DOIUrl":"https://doi.org/10.31861/bmj2022.02.17","url":null,"abstract":"The problems for Eidelman type equations and systems of equations are considered in this paper. They were the large part of scientific interests for Prof. Ivasyshen S.D. The results of investigations of Cauchy problem, initial-boundary and the inverse problems for this type of equations in bounded or unbounded domains are given. The results are represented as the estimates of the solutions, the integral representations of solutions, theorems of the existence, uniqueness and stability of solutions.","PeriodicalId":196726,"journal":{"name":"Bukovinian Mathematical Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132980987","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"WEAK R-SPACES AND UNIFORM LIMIT OF SEQUENCES OF THE FIRST BAIRE CLASS FUNCTIONS","authors":"Mykhaylo Lukan, O. Karlova","doi":"10.31861/bmj2019.02.039","DOIUrl":"https://doi.org/10.31861/bmj2019.02.039","url":null,"abstract":"","PeriodicalId":196726,"journal":{"name":"Bukovinian Mathematical Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124015115","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Let $f$ be an entire function with $f(0)=1$, $(lambda_n)_{ninmathbb N}$ be the sequence of its zeros, $n(t)=sum_{|lambda_n|le t}1$, $N(r)=int_0^r t^{-1}n(t), dt$, $r>0$, $h(varphi)$ be the indicator of $f$, and $F(z)=zf'(z)/f(z)$, $z=re^{ivarphi}$. An entire function $f$ is called a function of improved regular growth if for some $rhoin (0,+infty)$ and $rho_1in (0,rho)$, and a $2pi$-periodic $rho$-trigonometrically convex function $h(varphi)notequiv -infty$ there exists a set $Usubsetmathbb C$ contained in the union of disks with finite sum of radii and such that begin{equation*} log |{f(z)}|=|z|^rho h(varphi)+o(|z|^{rho_1}),quad Unotni z=re^{ivarphi}toinfty. end{equation*} In this paper, we prove that an entire function $f$ of order $rhoin (0,+infty)$ with zeros on a finite system of rays ${z: arg z=psi_{j}}$, $jin{1,ldots,m}$, $0lepsi_1