{"title":"Equivalence of two constructions for (widehat{sl}_2)-integrable hierarchies","authors":"Panpan Dang, Yajuan Li, Yuanyuan Zhang, Jipeng Cheng","doi":"10.1134/S0040577925040063","DOIUrl":"10.1134/S0040577925040063","url":null,"abstract":"<p> We discuss the equivalence between the Date–Jimbo–Kashiwara–Miwa (DJKM) construction and the Kac–Wakimoto (KW) construction of <span>(widehat{sl}_2)</span>-integrable hierarchies within the framework of bilinear equations. The DJKM method has achieved remarkable success in constructing integrable hierarchies associated with classical A, B, C, D affine Lie algebras. In contrast, the KW method exhibits broader applicability, as it can be employed even for exceptional E, F, G affine Lie algebras. However, a significant drawback of the KW construction lies in the great difficulty of obtaining Lax equations for the corresponding integrable hierarchies. Conversely, in the DJKM construction, Lax structures for numerous integrable hierarchies can be derived. The derivation of Lax equations from bilinear equations in the KW construction remains an open problem. Consequently, demonstrating the equivalent DJKM construction for the integrable hierarchies obtained via the KW construction would be highly beneficial for obtaining the corresponding Lax structures. In this paper, we use the language of lattice vertex algebras to establish the equivalence between the DJKM and KW methods in the <span>(widehat{sl}_2)</span>-integrable hierarchy for principal and homogeneous representations. </p>","PeriodicalId":797,"journal":{"name":"Theoretical and Mathematical Physics","volume":"223 1","pages":"597 - 623"},"PeriodicalIF":1.0,"publicationDate":"2025-04-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143875283","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Linear representations of the Lie algebra of the diffeomorphism group in (mathbb{R}^d)","authors":"M. I. Gozman","doi":"10.1134/S0040577925040014","DOIUrl":"10.1134/S0040577925040014","url":null,"abstract":"<p> A family of representations of the Lie algebra of the diffeomorphism group in <span>(mathbb{R}^d)</span> is studied. A method for constructing representations of this family is proposed. Equations for matrices describing the action of the Lie algebra on the representation space are obtained. It is shown that the developed formalism is suitable for describing representations under which fields of linear homogeneous geometric objects are transformed. The formalism is shown to allow describing representations for which the representation space vectors cannot be expressed in terms of fields of linear homogeneous geometric objects. An example of such a representation is studied. </p>","PeriodicalId":797,"journal":{"name":"Theoretical and Mathematical Physics","volume":"223 1","pages":"525 - 547"},"PeriodicalIF":1.0,"publicationDate":"2025-04-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143875286","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Asymptotic solution convergence to a traveling wave in the Kolmogorov–Petrovskii–Piskunov equation","authors":"L. A. Kalyakin","doi":"10.1134/S0040577925040038","DOIUrl":"10.1134/S0040577925040038","url":null,"abstract":"<p> For a semilinear parabolic partial differential equation, we consider an asymptotic solution that converges to a traveling wave at large times <span>(t)</span>. The velocity of such a wave is time dependent, and we construct the asymptotics as <span>(ttoinfty)</span>. We find that the asymptotics contains logarithms and cannot be constructed in the form of a power series. </p>","PeriodicalId":797,"journal":{"name":"Theoretical and Mathematical Physics","volume":"223 1","pages":"556 - 571"},"PeriodicalIF":1.0,"publicationDate":"2025-04-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143875285","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Explicit Bargmann-type isomorphism between Berezin and Smolyanov representations of bosonic Fock spaces","authors":"N. N. Shamarov, M. V. Shamolin","doi":"10.1134/S0040577925040105","DOIUrl":"10.1134/S0040577925040105","url":null,"abstract":"<p> We construct a Bargmann-type isomorphism defined by the one-particle part <span>(H)</span> of the Fock space <span>(Gamma(H))</span> for an infinite-dimensional space <span>(H)</span> with involution. The formulas obtained also make sense in the case <span>(dim H<infty)</span> and are closely related to the Segal–Bargmann space. Central to the construction is the notion of a shift-invariant distribution in the case of an infinite-dimensional domain of test functions. </p>","PeriodicalId":797,"journal":{"name":"Theoretical and Mathematical Physics","volume":"223 1","pages":"665 - 670"},"PeriodicalIF":1.0,"publicationDate":"2025-04-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143875423","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Feynman integral in QFT and white noise on a compactified version of space–time with a Lie group structure","authors":"J. Wawrzycki","doi":"10.1134/S0040577925040117","DOIUrl":"10.1134/S0040577925040117","url":null,"abstract":"<p> We present a rigorous construction of the Feynman integral on the compactified Einstein Universe using white noise calculus. Our construction of functional averaging can also be thought of as a solution to a problem posed by Bogoliubov and Shirkov. </p>","PeriodicalId":797,"journal":{"name":"Theoretical and Mathematical Physics","volume":"223 1","pages":"671 - 689"},"PeriodicalIF":1.0,"publicationDate":"2025-04-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143875421","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"On the Rayleigh–Schrödinger coefficients for the eigenvalues of regular perturbations of an anharmonic oscillator","authors":"Kh. K. Ishkin","doi":"10.1134/S0040577925040099","DOIUrl":"10.1134/S0040577925040099","url":null,"abstract":"<p> We identify a class of perturbations of a complex anharmonic oscillator <span>(H)</span> for which the known formulas for the Rayleigh–Schrödinger coefficients can be significantly simplified. We investigate the effect of the spectral instability of the operator <span>(H)</span> on the behavior of the sequence of first perturbative corrections. We show that if <span>(H)</span> is not self-adjoint and the perturbation is finite and has finite smoothness at the right end of its support, then this sequence exponentially increases at infinity. </p>","PeriodicalId":797,"journal":{"name":"Theoretical and Mathematical Physics","volume":"223 1","pages":"650 - 664"},"PeriodicalIF":1.0,"publicationDate":"2025-04-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143875422","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"On alleged solutions of the cubically nonlinear Schrödinger equation","authors":"H. W. Schürmann, V. S. Serov","doi":"10.1134/S004057792504004X","DOIUrl":"10.1134/S004057792504004X","url":null,"abstract":"<p> On the basis of analytic results, we present a numerical example that indicates the inconsistency of a widely used ansatz for the cubically nonlinear Schrödinger equation. </p>","PeriodicalId":797,"journal":{"name":"Theoretical and Mathematical Physics","volume":"223 1","pages":"572 - 575"},"PeriodicalIF":1.0,"publicationDate":"2025-04-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143875284","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"(Omega)-Spectrum in topological phases","authors":"E. A. Teplyakov","doi":"10.1134/S0040577925040026","DOIUrl":"10.1134/S0040577925040026","url":null,"abstract":"<p> Symmetry-protected topological phases are an active field of research in condensed matter physics. The classification of symmetry-protected topological phases is an important problem in mathematics and theoretical physics. In this paper, a direct approach based on the use of methods of homotopy theory and the theory of infinite loop spaces is proposed to describe the <span>(Omega)</span>-spectra and the generalized cohomology theories arising in the classification of topological phases. </p>","PeriodicalId":797,"journal":{"name":"Theoretical and Mathematical Physics","volume":"223 1","pages":"548 - 555"},"PeriodicalIF":1.0,"publicationDate":"2025-04-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143875290","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Evolution of spherical perturbations in the cosmological environment of the Higgs scalar field and an ideal scalar charged fluid","authors":"Yu. G. Ignat’ev","doi":"10.1134/S0040577925040087","DOIUrl":"10.1134/S0040577925040087","url":null,"abstract":"<p> A mathematical model of the evolution of spherical perturbations in an ideal cosmological scalar-charged fluid coupled to the Higgs field is constructed. A closed mathematical model of linear spherical perturbations in a cosmological medium of a scalar-charged ideal fluid with scalar Higgs interaction is formulated. It is shown that spherical perturbations of the Friedmann metric are possible only in the presence of an isotropic fluid. At singular points of the background cosmological model, perturbations of the metric do not occur and perturbations are described by a vacuum-field model. Exact solutions are obtained at singular points of the cosmological system; the scalar field perturbations are shown to be traveling waves in the case of a stable singular point of the cosmological system and exponentially growing standing waves in the case of an unstable singular point. Using numerical modeling, the formation of a stratified halo in the form of growing standing waves is shown. </p>","PeriodicalId":797,"journal":{"name":"Theoretical and Mathematical Physics","volume":"223 1","pages":"636 - 649"},"PeriodicalIF":1.0,"publicationDate":"2025-04-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143875333","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Cauchy matrix approach to the nonisospectral and variable-coefficient Kadomtsev–Petviashvili equation","authors":"Zhen Zhou, Xinyuan Zhang, Tong Shen, Chunxia Li","doi":"10.1134/S0040577925030031","DOIUrl":"10.1134/S0040577925030031","url":null,"abstract":"<p> Cauchy matrix approach is developed to construct the nonisospectral and variable-coefficient equations and study their integrability. We derive the nonisospectral and variable-coefficient Kadomtsev–Petviashvili ( n-vcKP) equation, which includes the standard KP equation and the nonisospectral and variable-coefficient KdV equation as special cases. The connection of the <span>(tau)</span> function of the n-vcKP equation with the Cauchy matrix approach is clarified. The Lax pair for the n-vcKP equation is derived in a systematic way. Two types of exact solutions are found by solving the corresponding Sylvester equation. </p>","PeriodicalId":797,"journal":{"name":"Theoretical and Mathematical Physics","volume":"222 3","pages":"401 - 413"},"PeriodicalIF":1.0,"publicationDate":"2025-03-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143688532","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}