{"title":"Non-Resonant Conditions for the Klein – Gordon Equation on the Circle","authors":"Roberto Feola, Jessica Elisa Massetti","doi":"10.1134/S1560354724040026","DOIUrl":"10.1134/S1560354724040026","url":null,"abstract":"<div><p>We consider the infinite-dimensional vector of frequencies <span>(omega(mathtt{m})=(sqrt{j^{2}+mathtt{m}})_{jinmathbb{Z}})</span>, <span>(mathtt{m}in[1,2])</span>\u0000arising from a linear Klein – Gordon equation on the one-dimensional torus and prove that there exists a positive measure set of masses <span>(mathtt{m}^{prime})</span>s for which <span>(omega(mathtt{m}))</span> satisfies a Diophantine condition similar to the one introduced by Bourgain in [14],\u0000in the context of the Schrödinger equation with convolution potential.\u0000The main difficulties we have to deal with are\u0000the asymptotically linear nature of the (infinitely many) <span>(omega_{j}^{prime})</span>s and the degeneracy coming from having only one parameter at disposal for their modulation.\u0000As an application we provide estimates on the inverse of the adjoint action of the associated quadratic Hamiltonian on homogenenous polynomials of any degree in Gevrey category.</p></div>","PeriodicalId":752,"journal":{"name":"Regular and Chaotic Dynamics","volume":"29 and Dmitry Treschev)","pages":"541 - 564"},"PeriodicalIF":0.8,"publicationDate":"2024-08-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141935536","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 Elliptic Lower-Dimensional Invariant Tori with Prescribed Frequencies in Hamiltonian Systems with Small Parameters","authors":"Hanru Zou, Junxiang Xu","doi":"10.1134/S156035472404004X","DOIUrl":"10.1134/S156035472404004X","url":null,"abstract":"<div><p>In this paper we consider the persistence of elliptic lower-dimensional invariant tori with prescribed frequencies in Hamiltonian systems with small parameters. Under the Brjuno nondegeneracy condition,\u0000if the prescribed frequencies satisfy a Diophantine condition, by the KAM technique we prove that for most of small parameters in the sense of Lebesgue measure, the Hamiltonian systems admit a lower-dimensional\u0000invariant torus whose frequency vector is a dilation of the prescribed frequencies.</p></div>","PeriodicalId":752,"journal":{"name":"Regular and Chaotic Dynamics","volume":"29 and Dmitry Treschev)","pages":"583 - 604"},"PeriodicalIF":0.8,"publicationDate":"2024-08-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141935550","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}
Chiara Caracciolo, Ugo Locatelli, Marco Sansottera, Mara Volpi
{"title":"3D Orbital Architecture of Exoplanetary Systems: KAM-Stability Analysis","authors":"Chiara Caracciolo, Ugo Locatelli, Marco Sansottera, Mara Volpi","doi":"10.1134/S1560354724040038","DOIUrl":"10.1134/S1560354724040038","url":null,"abstract":"<div><p>We study the KAM-stability of several single star two-planet\u0000nonresonant extrasolar systems. It is likely that the observed\u0000exoplanets are the most massive of the system considered. Therefore,\u0000their robust stability is a crucial and necessary condition for the\u0000long-term survival of the system when considering potential\u0000additional exoplanets yet to be seen. Our study is based on the\u0000construction of a combination of lower-dimensional elliptic and KAM\u0000tori, so as to better approximate the dynamics in the framework of\u0000accurate secular models. For each extrasolar system, we explore the\u0000parameter space of both inclinations: the one with respect to the\u0000line of sight and the mutual inclination between the planets. Our\u0000approach shows that remarkable inclinations, resulting in\u0000three-dimensional architectures that are far from being coplanar,\u0000can be compatible with the KAM stability of the system. We find\u0000that the highest values of the mutual inclinations are comparable to\u0000those of the few systems for which the said inclinations are determined\u0000by the observations.</p></div>","PeriodicalId":752,"journal":{"name":"Regular and Chaotic Dynamics","volume":"29 and Dmitry Treschev)","pages":"565 - 582"},"PeriodicalIF":0.8,"publicationDate":"2024-08-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1134/S1560354724040038.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141935476","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Persistence of Multiscale Degenerate Invariant Tori in Reversible Systems with Degenerate Frequency Mapping","authors":"Xiaomei Yang, Junxiang Xu","doi":"10.1134/S1560354724040051","DOIUrl":"10.1134/S1560354724040051","url":null,"abstract":"<div><p>This paper considers a class of nearly integrable reversible systems\u0000whose unperturbed part has a degenerate frequency mapping and a degenerate equilibrium point.\u0000Based on some KAM techniques\u0000and the topological degree theory, we prove the persistence of multiscale degenerate hyperbolic lower-dimensional invariant tori with prescribed frequencies.</p></div>","PeriodicalId":752,"journal":{"name":"Regular and Chaotic Dynamics","volume":"29 and Dmitry Treschev)","pages":"605 - 619"},"PeriodicalIF":0.8,"publicationDate":"2024-08-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141935478","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":"Isolated Diophantine Numbers","authors":"Fernando Argentieri, Luigi Chierchia","doi":"10.1134/S156035472455001X","DOIUrl":"10.1134/S156035472455001X","url":null,"abstract":"<div><p>In this note, we discuss the topology of Diophantine numbers, giving simple explicit\u0000examples of Diophantine isolated numbers (among those with the same Diophantine constants),\u0000showing that <i>Diophantine sets are not always Cantor sets</i>.</p><p>General properties of isolated Diophantine numbers are also briefly discussed.</p></div>","PeriodicalId":752,"journal":{"name":"Regular and Chaotic Dynamics","volume":"29 and Dmitry Treschev)","pages":"536 - 540"},"PeriodicalIF":0.8,"publicationDate":"2024-07-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1134/S156035472455001X.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141576048","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Nineteen Fifty-Four: Kolmogorov’s New “Metrical Approach” to Hamiltonian Dynamics","authors":"Luigi Chierchia, Isabella Fascitiello","doi":"10.1134/S1560354724550021","DOIUrl":"10.1134/S1560354724550021","url":null,"abstract":"<div><p>We review Kolmogorov’s 1954 fundamental paper <i>On the persistence of conditionally periodic motions under a small change in the Hamilton function</i> (Dokl. akad. nauk SSSR, 1954, vol. <b>98</b>, pp. 527–530), both from the historical and the mathematical point of view.\u0000In particular, we discuss Theorem 2 (which deals with the measure in phase space of persistent tori), the proof of which is not discussed at all by Kolmogorov, notwithstanding its centrality in his program in classical mechanics.</p><p>In Appendix, an interview (May 28, 2021) to Ya. Sinai on Kolmogorov’s legacy in classical mechanics is reported.</p></div>","PeriodicalId":752,"journal":{"name":"Regular and Chaotic Dynamics","volume":"29 and Dmitry Treschev)","pages":"517 - 535"},"PeriodicalIF":0.8,"publicationDate":"2024-07-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141578145","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":"KAM for Vortex Patches","authors":"Massimiliano Berti","doi":"10.1134/S1560354724540013","DOIUrl":"10.1134/S1560354724540013","url":null,"abstract":"<div><p>In the last years substantial mathematical progress has been made in KAM theory\u0000for <i>quasi-linear</i>/fully nonlinear\u0000Hamiltonian partial differential equations, notably for\u0000water waves and Euler equations.\u0000In this survey we focus on recent advances in quasi-periodic vortex patch\u0000solutions of the <span>(2d)</span>-Euler equation in <span>(mathbb{R}^{2})</span>\u0000close to uniformly rotating Kirchhoff elliptical vortices,\u0000with aspect ratios belonging to a set of asymptotically full Lebesgue measure.\u0000The problem is reformulated into a quasi-linear Hamiltonian equation for a radial displacement from the ellipse. A major difficulty of the KAM proof is the presence of a zero normal mode frequency, which is due to the conservation of the angular momentum. The key novelty to overcome this degeneracy is to perform a perturbative symplectic reduction of the angular momentum, introducing it as a symplectic variable in the spirit of the Darboux – Carathéodory theorem of symplectic rectification, valid in finite dimension.\u0000This approach is particularly delicate in an infinite-dimensional phase space: our symplectic\u0000change of variables is a nonlinear modification of the transport flow generated by the angular\u0000momentum itself.</p></div>","PeriodicalId":752,"journal":{"name":"Regular and Chaotic Dynamics","volume":"29 and Dmitry Treschev)","pages":"654 - 676"},"PeriodicalIF":0.8,"publicationDate":"2024-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141501790","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":"Maximal Tori in Infinite-Dimensional Hamiltonian Systems: a Renormalisation Group Approach","authors":"Livia Corsi, Guido Gentile, Michela Procesi","doi":"10.1134/S1560354724540025","DOIUrl":"10.1134/S1560354724540025","url":null,"abstract":"<div><p>We study the existence of infinite-dimensional invariant tori in a mechanical system of infinitely many rotators weakly interacting with each other.\u0000We consider explicitly interactions depending only on the angles,\u0000with the aim of discussing in a simple case the analyticity properties to be required on the perturbation of the integrable system\u0000in order to ensure the persistence of a large measure set of invariant tori with finite energy.\u0000The proof we provide of the persistence of the invariant tori implements the renormalisation group scheme based on the tree formalism, i. e., the graphical representation of the solutions of the equations of motion in\u0000terms of trees, which has been widely used in finite-dimensional problems. The method is very effectual and flexible:\u0000it naturally extends, once the functional setting has been fixed, to the infinite-dimensional case with only minor technical-natured adaptations.</p></div>","PeriodicalId":752,"journal":{"name":"Regular and Chaotic Dynamics","volume":"29 and Dmitry Treschev)","pages":"677 - 715"},"PeriodicalIF":0.8,"publicationDate":"2024-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141501789","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":"Geodesics with Unbounded Speed on Fluctuating Surfaces","authors":"Andrew Clarke","doi":"10.1134/S1560354724030018","DOIUrl":"10.1134/S1560354724030018","url":null,"abstract":"<div><p>We construct <span>(C^{infty})</span> time-periodic fluctuating surfaces in <span>(mathbb{R}^{3})</span> such that the corresponding non-autonomous geodesic flow has orbits along which the energy, and thus the speed goes to infinity. We begin with a static surface <span>(M)</span> in <span>(mathbb{R}^{3})</span> on which the geodesic flow (with respect to the induced metric from <span>(mathbb{R}^{3})</span>) has a hyperbolic periodic orbit with a transverse homoclinic orbit. Taking this hyperbolic periodic orbit in an interval of energy levels gives us a normally hyperbolic invariant manifold <span>(Lambda)</span>, the stable and unstable manifolds of which have a transverse homoclinic intersection. The surface <span>(M)</span> is embedded into <span>(mathbb{R}^{3})</span> via a near-identity time-periodic embedding <span>(G:Mtomathbb{R}^{3})</span>. Then the pullback under <span>(G)</span> of the induced metric on <span>(G(M))</span> is a time-periodic metric on <span>(M)</span>, and the corresponding geodesic flow has a normally hyperbolic invariant manifold close to <span>(Lambda)</span>, with stable and unstable manifolds intersecting transversely along a homoclinic channel. Perturbative techniques are used to calculate the scattering map and construct pseudo-orbits that move up along the cylinder. The energy tends to infinity along such pseudo-orbits. Finally, existing shadowing methods are applied to establish the existence of actual orbits of the non-autonomous geodesic flow shadowing these pseudo-orbits. In the same way we prove the existence of oscillatory trajectories, along which the limit inferior of the energy is finite, but the limit superior is infinite.</p></div>","PeriodicalId":752,"journal":{"name":"Regular and Chaotic Dynamics","volume":"29 3","pages":"435 - 450"},"PeriodicalIF":0.8,"publicationDate":"2024-05-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141197649","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}