{"title":"New Remarks on the Scattering for a Perturbed Polyharmonic Operator","authors":"Grigori Rozenblum","doi":"10.1134/S1234567825030085","DOIUrl":"10.1134/S1234567825030085","url":null,"abstract":"<p> We obtain sufficient conditions for the perturbation of the power of the resolvent of the polyharmonic operator under a perturbation by a highly singular potential to belong to Schatten classes. </p>","PeriodicalId":575,"journal":{"name":"Functional Analysis and Its Applications","volume":"59 3","pages":"321 - 329"},"PeriodicalIF":0.7,"publicationDate":"2025-10-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145316155","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":"A Generalized Birman–Schwinger Principle and Applications to One-Dimensional Schrödinger Operators with Distributional Potentials","authors":"Fritz Gesztesy, Roger Nichols","doi":"10.1134/S1234567825030024","DOIUrl":"10.1134/S1234567825030024","url":null,"abstract":"<p> Given a self-adjoint operator <span>(H_0)</span> bounded from below in a complex, separable Hilbert space <span>(mathcal H)</span>, the corresponding scale of spaces <span>(mathcal H_{+1}(H_0) subset mathcal H subset mathcal H_{-1}(H_0)=[mathcal H_{+1}(H_0)]^*)</span>, and a fixed <span>(Vin mathcal B(mathcal H_{+1}(H_0),mathcal H_{-1}(H_0)))</span>, we define the operator-valued map <span>(A_V(,cdot,)colon rho(H_0)to mathcal B(mathcal H))</span> by </p><p> where <span>(rho(H_0))</span> denotes the resolvent set of <span>(H_0)</span>. Assuming that <span>(A_V(z))</span> is compact for some <span>(z=z_0in rho(H_0))</span> and has norm strictly less than one for some <span>(z=E_0in (-infty,0))</span>, we employ an abstract version of Tiktopoulos’ formula to define an operator <span>(H)</span> in <span>(mathcal H)</span> that is formally realized as the sum of <span>(H_0)</span> and <span>(V)</span>. We then establish a Birman–Schwinger principle for <span>(H)</span> in which <span>(A_V(,cdot,))</span> plays the role of the Birman–Schwinger operator: <span>(lambda_0in rho(H_0))</span> is an eigenvalue of <span>(H)</span> if and only if <span>(1)</span> is an eigenvalue of <span>(A_V(lambda_0))</span>. Furthermore, the geometric (but not necessarily the algebraic) multiplicities of <span>(lambda_0)</span> and <span>(1)</span> as eigenvalues of <span>(H)</span> and <span>(A_V(lambda_0))</span>, respectively, coincide. </p><p> As a concrete application, we consider one-dimensional Schrödinger operators with <span>(H^{-1}(mathbb{R}))</span> distributional potentials. </p>","PeriodicalId":575,"journal":{"name":"Functional Analysis and Its Applications","volume":"59 3","pages":"224 - 250"},"PeriodicalIF":0.7,"publicationDate":"2025-10-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145316345","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}
Elena Zhizhina, Andrey Piatnitski, Vladimir Sloushch, Tatiana Suslina
{"title":"Homogenization of the Lévy-type Operators","authors":"Elena Zhizhina, Andrey Piatnitski, Vladimir Sloushch, Tatiana Suslina","doi":"10.1134/S1234567825030036","DOIUrl":"10.1134/S1234567825030036","url":null,"abstract":"<p> In <span>(L_2(mathbb R^d))</span>, we consider a selfadjoint operator <span>({mathbb A}_varepsilon)</span>, <span>(varepsilon >0)</span>, of the form </p><p> where <span>(0< alpha < 2)</span>. It is assumed that a function <span>(mu(mathbf{x},mathbf{y}))</span> is bounded, positive definite, periodic in each variable, and is such that <span>(mu(mathbf{x},mathbf{y})=mu(mathbf{y},mathbf{x}))</span>. A rigorous definition of the operator <span>({mathbb A}_varepsilon)</span> is given in terms of the corresponding quadratic form. It is proved that the resolvent <span>(({mathbb A}_varepsilon+I)^{-1})</span> converges in the operator norm on <span>(L_2(mathbb R^d))</span> to the operator <span>(({mathbb A}^0+I)^{-1})</span> as <span>(varepsilonto 0)</span>. Here, <span>({mathbb A}^0)</span> is an effective operator of the same form with the constant coefficient <span>(mu^0)</span> equal to the mean value of <span>(mu(mathbf{x},mathbf{y}))</span>. We obtain an error estimate of order <span>(O(varepsilon^alpha))</span> for <span>(0< alpha < 1)</span>, <span>(O(varepsilon (1+| operatorname{ln} varepsilon|)^2))</span> for <span>( alpha=1)</span>, and <span>(O(varepsilon^{2- alpha}))</span> for <span>(1< alpha < 2)</span>. In the case where <span>(1< alpha < 2)</span>, the result is refined by taking the correctors into account. </p>","PeriodicalId":575,"journal":{"name":"Functional Analysis and Its Applications","volume":"59 3","pages":"251 - 257"},"PeriodicalIF":0.7,"publicationDate":"2025-10-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145316346","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":"Unbounded Integral Hankel Operators","authors":"Alexander Pushnitski, Sergei R. Treil","doi":"10.1134/S1234567825030073","DOIUrl":"10.1134/S1234567825030073","url":null,"abstract":"<p> For a wide class of unbounded integral Hankel operators on the positive half-line, we prove essential self-adjointness on the set of smooth compactly supported functions. </p>","PeriodicalId":575,"journal":{"name":"Functional Analysis and Its Applications","volume":"59 3","pages":"297 - 320"},"PeriodicalIF":0.7,"publicationDate":"2025-10-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145316154","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":"Eigenvalue Estimates for the Coulombic One-Particle Density Matrix and the Kinetic Energy Density Matrix","authors":"Alexander Sobolev","doi":"10.1134/S1234567825030103","DOIUrl":"10.1134/S1234567825030103","url":null,"abstract":"<p> Consider a bound state (an eigenfunction) <span>(psi)</span> of an atom with <span>(N)</span> electrons. We study the spectra of the one-particle density matrix <span>(gamma)</span> and the one-particle kinetic energy density matrix <span>(tau)</span> associated with <span>(psi)</span>. The paper contains two results. First, we obtain the bounds <span>(lambda_k(gamma)le C k^{-8/3})</span> and <span>(lambda_k(tau)le C k^{-2})</span> with some positive constants <span>(C)</span> that depend explicitly on the eigenfunction <span>(psi)</span>. The sharpness of these bounds is confirmed by the asymptotic results obtained by the author in earlier papers. The advantage of these bounds over the ones derived by the author previously is their explicit dependence on the eigenfunction. Moreover, their new proofs are more elementary and direct. The second result is new, and it pertains to the case where the eigenfunction <span>(psi)</span> vanishes at the particle coalescence points. In particular, this is true for totally antisymmetric <span>(psi)</span>. In this case, the eigenfunction <span>(psi)</span> exhibits enhanced regularity at the coalescence points, which leads to the faster decay of the eigenvalues: <span>(lambda_k(gamma)le C k^{-10/3})</span> and <span>(lambda_k(tau)le C k^{-8/3})</span>. </p><p> The proofs rely on estimates for the derivatives of the eigenfunction <span>(psi)</span> that depend explicitly on the distance to the coalescence points. Some of these estimates are borrowed directly from, and some are derived using the methods of, a recent paper by S. Fournais and T. Ø. Sørensen. </p>","PeriodicalId":575,"journal":{"name":"Functional Analysis and Its Applications","volume":"59 3","pages":"347 - 365"},"PeriodicalIF":0.7,"publicationDate":"2025-10-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145316347","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}
Anna Zernova, Alexei Ilyin, Ari Laptev, Lukas Schimmer
{"title":"Eigenvalues of Non-Selfadjoint Functional Difference Operators","authors":"Anna Zernova, Alexei Ilyin, Ari Laptev, Lukas Schimmer","doi":"10.1134/S1234567825030048","DOIUrl":"10.1134/S1234567825030048","url":null,"abstract":"<p> Using the well known approach developed in the papers of B. Davies and his co-authors, we obtain inequalities for the location of possible complex eigenvalues of non-selfadjoint functional difference operators. When studying the sharpness of the main result, we discovered that complex potentials can create resonances. </p>","PeriodicalId":575,"journal":{"name":"Functional Analysis and Its Applications","volume":"59 3","pages":"258 - 270"},"PeriodicalIF":0.7,"publicationDate":"2025-10-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145316340","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":"Spectral Asymptotics for Robin Laplacians on Lipschitz Sets","authors":"Simon Larson, Rupert L. Frank","doi":"10.1134/S1234567825030061","DOIUrl":"10.1134/S1234567825030061","url":null,"abstract":"<p> We prove two-term spectral asymptotics for the Riesz means of the eigenvalues of the Laplacian on a Lipschitz domain with Robin boundary conditions. The second term is the same as in the case of Neumann boundary conditions. This is valid for Riesz means of arbitrary positive order. For orders at least one and under additional assumptions on the function determining the boundary conditions, we derive leading order asymptotics for the difference between Riesz means of Robin and Neumann eigenvalues. </p>","PeriodicalId":575,"journal":{"name":"Functional Analysis and Its Applications","volume":"59 3","pages":"277 - 296"},"PeriodicalIF":0.7,"publicationDate":"2025-10-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145316234","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":"The Speed of Convergence Under the Kolmogorov–Smirnov Metric in the Soshnikov Central Limit Theorem for the Sine Process","authors":"Alexander Bufetov","doi":"10.1134/S1234567825020028","DOIUrl":"10.1134/S1234567825020028","url":null,"abstract":"<p> For rescaled additive functionals of the sine process, upper bounds are obtained for their speed of convergence to the Gaussian distribution with respect to the Kolmogorov–Smirnov metric. Under scaling with coefficient <span>(R>1)</span>, the Kolmogorov–Smirnov distance is bounded from above by <span>(c/log R)</span> for a smooth function, and by <span>(c/R)</span> for a function holomorphic in a horizontal strip. </p>","PeriodicalId":575,"journal":{"name":"Functional Analysis and Its Applications","volume":"59 2","pages":"114 - 118"},"PeriodicalIF":0.7,"publicationDate":"2025-07-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145160519","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 Spectrum of the Differential Operators of Odd Order with (mathcal{PT})-Symmetric Coefficients","authors":"Oktay Veliev","doi":"10.1134/S123456782502003X","DOIUrl":"10.1134/S123456782502003X","url":null,"abstract":"<p> In this paper, we consider the Bloch eigenvalues and spectrum of the non-self-adjoint differential operator <span>(L)</span> generated by the differential expression of odd order <span>(n)</span> with periodic <span>(mathcal{PT})</span>-symmetric coefficients, where <span>(n>1)</span>. We study the localizations of the Bloch eigenvalues and the structure of the spectrum. Moreover, we find conditions on the norm of the coefficients under which the spectrum of <span>(L)</span> is purely real and coincides with the real line. </p>","PeriodicalId":575,"journal":{"name":"Functional Analysis and Its Applications","volume":"59 2","pages":"119 - 125"},"PeriodicalIF":0.7,"publicationDate":"2025-07-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145161918","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}