{"title":"Ricci Solitons on Generalized Sasakian-Space-Forms with Kenmotsu Metric","authors":"Savita Rani, Ram Shankar Gupta","doi":"10.1134/s0001434624010231","DOIUrl":"https://doi.org/10.1134/s0001434624010231","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p> We study Ricci solitons and <span>(ast)</span>-Ricci solitons on generalized Sasakian-space-forms (GSSF) <span>(M^{2n+1} (f_1, f_2, f_3))</span> with parallel <span>(ast)</span>-Ricci tensor. We find that if GSSF <span>(M^{2n+1} (f_1, f_2, f_3))</span> with Kenmotsu metric admits a Ricci soliton or a <span>(ast)</span>-Ricci soliton, then <span>(f_1=-1)</span> and <span>(f_2=f_3=0)</span>. Moreover, the Ricci soliton is expanding, and the <span>(ast)</span>-Ricci soliton is steady. Further, we provide some examples. </p>","PeriodicalId":18294,"journal":{"name":"Mathematical Notes","volume":"21 1","pages":""},"PeriodicalIF":0.6,"publicationDate":"2024-04-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140882539","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":"Asymptotics of Fundamental Solutions of Parabolic Problems","authors":"V. G. Danilov","doi":"10.1134/s0001434624010176","DOIUrl":"https://doi.org/10.1134/s0001434624010176","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p> We present several methods for constructing the asymptotics of the fundamental solution of Fokker–Planck–Kolmogorov-type parabolic equations with a small parameter both for small and finite positive times. </p>","PeriodicalId":18294,"journal":{"name":"Mathematical Notes","volume":"20 1","pages":""},"PeriodicalIF":0.6,"publicationDate":"2024-04-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140882608","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":"Uniform Rational Approximation of Even and Odd Continuations of Functions","authors":"T. S. Mardvilko","doi":"10.1134/s0001434624010206","DOIUrl":"https://doi.org/10.1134/s0001434624010206","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p> The behavior of the best rational approximations of an odd continuation of a function is studied. It is shown that without additional conditions on the smoothness of the function, it is impossible to estimate the best rational approximation of the odd continuation of the function on <span>([-1,1])</span> in terms of the best rational approximation of the original function on <span>([0,1])</span>. A sharp upper bound is found for the best rational approximations of an even (odd) continuation of a function in terms of an odd (even) continuation and an extremal Blaschke product. </p>","PeriodicalId":18294,"journal":{"name":"Mathematical Notes","volume":"16 1","pages":""},"PeriodicalIF":0.6,"publicationDate":"2024-04-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140882609","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":"Comparison of Purely Greedy and Orthogonal Greedy Algorithm","authors":"K. S. Vishnevetskiy","doi":"10.1134/s0001434624010048","DOIUrl":"https://doi.org/10.1134/s0001434624010048","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p> Conditions for a dictionary in a Hilbert space are obtained that are necessary or sufficient for the coincidence of purely greedy and orthogonal greedy algorithms with respect to this dictionary. </p>","PeriodicalId":18294,"journal":{"name":"Mathematical Notes","volume":"28 1","pages":""},"PeriodicalIF":0.6,"publicationDate":"2024-04-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140805216","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 Second Order Sufficient Optimality Conditions for a Problem of Mathematical Programming","authors":"A. V. Arutyunov, S. E. Zhukovskiy","doi":"10.1134/s0001434624010140","DOIUrl":"https://doi.org/10.1134/s0001434624010140","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p> We consider the constrained optimization problem for a smooth function defined on a Banach space with smooth constraints of equality and inequality type. We show that for this problem, under the known sufficient second-order optimality conditions, the set of Lagrange multipliers can be replaced by a smaller set. </p>","PeriodicalId":18294,"journal":{"name":"Mathematical Notes","volume":"17 1","pages":""},"PeriodicalIF":0.6,"publicationDate":"2024-04-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140805294","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":"Existence, Asymptotics, and Lyapunov Stability of Solutions of Periodic Parabolic Problems for Tikhonov-Type Reaction–Diffusion Systems","authors":"N. N. Nefedov","doi":"10.1134/s000143462401022x","DOIUrl":"https://doi.org/10.1134/s000143462401022x","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p> We study a new class of time-periodic solutions of singularly perturbed systems of reaction–diffusion equations in the case of a fast and a slow equation, which are usually called Tikhonov-type systems. A boundary layer asymptotics of solutions is constructed, the existence of solutions with this asymptotics is proved, and conditions for the Lyapunov asymptotic stability of these solutions treated as solutions of the corresponding initial–boudary value problems are obtained. </p>","PeriodicalId":18294,"journal":{"name":"Mathematical Notes","volume":"28 1","pages":""},"PeriodicalIF":0.6,"publicationDate":"2024-04-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140882603","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 Sum of Negative Eigenvalues of the Three-Dimensional Schrödinger Operator","authors":"A. R. Aliev, E. H. Eyvazov","doi":"10.1134/s0001434624010139","DOIUrl":"https://doi.org/10.1134/s0001434624010139","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p> M. Demuth and G. Katriel (arXiv: math.SP/0802.2032) proved the finiteness of the sum of negative eigenvalues of the <span>(d)</span>-dimensional Schrödinger operator under certain conditions on the electrical potential for <span>(dge 4)</span>. They also posed the following question: Is the restriction <span>(dge 4)</span> a disadvantage of the method, or does it reflect the actual situation? In the present paper, we prove that the technique in the cited paper also works for the three-dimensional Schrödinger operator with Kato potential whose negative part is an integrable function and that this method does not apply to the two-dimensional Schrödinger operator. </p>","PeriodicalId":18294,"journal":{"name":"Mathematical Notes","volume":"12 1","pages":""},"PeriodicalIF":0.6,"publicationDate":"2024-04-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140805287","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":"Dominant Sets for Model Spaces in Several Variables","authors":"A. B. Aleksandrov, E. S. Dubtsov","doi":"10.1134/s0001434624010127","DOIUrl":"https://doi.org/10.1134/s0001434624010127","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p> Let <span>(I)</span> be an inner function in the domain <span>(mathcal{D}=B_{n_1}times B_{n_2}times dots times B_{n_k})</span>, where <span>(B_n)</span> is the open unit ball in <span>(mathbb{C}^n)</span>, <span>(nge 1)</span>. We construct dominant sets for the space <span>(H^2 ominus I H^2)</span>, where <span>(H^2= H^2(mathcal{D}))</span> is the standard Hardy space. </p>","PeriodicalId":18294,"journal":{"name":"Mathematical Notes","volume":"47 1","pages":""},"PeriodicalIF":0.6,"publicationDate":"2024-04-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140889934","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 Algebraic Properties of Integrals of Products of Some Hypergeometric Functions","authors":"V. A. Gorelov","doi":"10.1134/s0001434624010164","DOIUrl":"https://doi.org/10.1134/s0001434624010164","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p> Indefinite integrals of products of generalized hypergeometric functions satisfying first- order differential equations are considered. Necessary and sufficient conditions for the algebraic independence of the set of these integrals and of their values at algebraic points are studied. All algebraic identities arising in this case are found in closed form. </p>","PeriodicalId":18294,"journal":{"name":"Mathematical Notes","volume":"11 1","pages":""},"PeriodicalIF":0.6,"publicationDate":"2024-04-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140882611","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":"Estimate for the Rate of Uniform Convergence of the Fourier Series of a Continuous Periodic Function of Bounded $$p$$ -Variation","authors":"T. Yu. Semenova","doi":"10.1134/s0001434624010243","DOIUrl":"https://doi.org/10.1134/s0001434624010243","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p> We obtain an estimate for the convergence rate of the Fourier series of a continuous periodic function in terms of the modulus of continuity of the function and the value of its <span>(p)</span>-variation. We prove that the leading term of the estimate is sharp. </p>","PeriodicalId":18294,"journal":{"name":"Mathematical Notes","volume":"32 1","pages":""},"PeriodicalIF":0.6,"publicationDate":"2024-04-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140882731","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}