{"title":"Moment maps and isoparametric hypersurfaces in spheres — Grassmannian cases","authors":"Shinobu Fujii","doi":"10.1016/j.difgeo.2023.102072","DOIUrl":"https://doi.org/10.1016/j.difgeo.2023.102072","url":null,"abstract":"<div><p>We expect that every Cartan–Münzner polynomial of degree four can be described as a squared-norm of a moment map for a Hamiltonian action. Our expectation is known to be true for Hermitian cases, that is, those obtained from the isotropy representations of compact irreducible Hermitian symmetric spaces of rank two. In this paper, we prove that our expectation is true for the Cartan–Münzner polynomials obtained from the isotropy representations of Grassmannian manifolds of rank two over <span><math><mi>R</mi></math></span>, <span><math><mi>C</mi></math></span> or <span><math><mi>H</mi></math></span>. The quaternion cases are the first non-Hermitian examples that our expectation is verified.</p></div>","PeriodicalId":51010,"journal":{"name":"Differential Geometry and its Applications","volume":"91 ","pages":"Article 102072"},"PeriodicalIF":0.5,"publicationDate":"2023-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91959400","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":"Rarita-Schwinger fields on nearly Kähler manifolds","authors":"Soma Ohno , Takuma Tomihisa","doi":"10.1016/j.difgeo.2023.102068","DOIUrl":"https://doi.org/10.1016/j.difgeo.2023.102068","url":null,"abstract":"<div><p>We study Rarita-Schwinger fields on 6-dimensional compact strict nearly Kähler manifolds. In order to investigate them, we clarify the relationship between some differential operators for the Hermitian connection and the Levi-Civita connection. As a result, we show that the space of Rarita-Schwinger fields coincides with the space of harmonic 3-forms. Applying the same technique to deformation theory, we also find that the space of infinitesimal deformations of Killing spinors coincides with the direct sum of a certain eigenspace of the Laplace operator and the space of Killing spinors.</p></div>","PeriodicalId":51010,"journal":{"name":"Differential Geometry and its Applications","volume":"91 ","pages":"Article 102068"},"PeriodicalIF":0.5,"publicationDate":"2023-10-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0926224523000943/pdfft?md5=630b11c08c25cdf884db86fa0e59240a&pid=1-s2.0-S0926224523000943-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"92045302","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":"Periodic discrete Darboux transforms","authors":"Joseph Cho , Katrin Leschke , Yuta Ogata","doi":"10.1016/j.difgeo.2023.102065","DOIUrl":"https://doi.org/10.1016/j.difgeo.2023.102065","url":null,"abstract":"<div><p>We express Darboux transformations of discrete polarised curves as parallel sections of discrete connections in the quaternionic formalism. This immediately leads to the linearisation of the monodromy of the transformation. We also consider the integrable reduction to the case of discrete bicycle correspondence. Applying our method to the case of discrete circles, we obtain closed-form discrete parametrisations of all (closed) Darboux transforms and (closed) bicycle correspondences.</p></div>","PeriodicalId":51010,"journal":{"name":"Differential Geometry and its Applications","volume":"91 ","pages":"Article 102065"},"PeriodicalIF":0.5,"publicationDate":"2023-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49749602","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":"Geometric integral formulas of cylinders within slabs","authors":"Ximo Gual-Arnau","doi":"10.1016/j.difgeo.2023.102066","DOIUrl":"https://doi.org/10.1016/j.difgeo.2023.102066","url":null,"abstract":"<div><p>We present new expressions for the integrals of mean curvature of domains in <span><math><msup><mrow><mi>R</mi></mrow><mrow><mi>n</mi></mrow></msup></math></span> by means of sections with cylinders. Then, we combine these expressions with the corresponding version of the invariant density of affine subspaces in <span><math><msup><mrow><mi>R</mi></mrow><mrow><mi>n</mi></mrow></msup></math></span>, in order to obtain pseudo-rotational formulae for all the integrals of mean curvature of ∂<em>K</em>. As particular cases, we present pseudo-rotational integral formulas for the volume, area, integral of mean curvature, and Euler-Poincaré characteristic of a connected domain of <span><math><msup><mrow><mi>R</mi></mrow><mrow><mn>3</mn></mrow></msup></math></span>, whose boundary is a surface, considering slabs in <span><math><msup><mrow><mi>R</mi></mrow><mrow><mn>3</mn></mrow></msup></math></span> whose central plane passes through a fixed point, and cylinders contained in these slabs.</p></div>","PeriodicalId":51010,"journal":{"name":"Differential Geometry and its Applications","volume":"91 ","pages":"Article 102066"},"PeriodicalIF":0.5,"publicationDate":"2023-10-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49749802","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":"Lower bounds for isoperimetric profiles and Yamabe constants","authors":"Juan Miguel Ruiz, Areli Vázquez Juárez","doi":"10.1016/j.difgeo.2023.102069","DOIUrl":"https://doi.org/10.1016/j.difgeo.2023.102069","url":null,"abstract":"<div><p>We estimate explicit lower bounds for the isoperimetric profiles of the Riemannian product of a compact manifold and the Euclidean space with the flat metric, <span><math><mo>(</mo><msup><mrow><mi>M</mi></mrow><mrow><mi>m</mi></mrow></msup><mo>×</mo><msup><mrow><mi>R</mi></mrow><mrow><mi>n</mi></mrow></msup><mo>,</mo><mi>g</mi><mo>+</mo><msub><mrow><mi>g</mi></mrow><mrow><mi>E</mi></mrow></msub><mo>)</mo></math></span>, <span><math><mi>m</mi><mo>,</mo><mi>n</mi><mo>></mo><mn>1</mn></math></span>. In particular, we introduce a lower bound for the isoperimetric profile of <span><math><msup><mrow><mi>M</mi></mrow><mrow><mi>m</mi></mrow></msup><mo>×</mo><msup><mrow><mi>R</mi></mrow><mrow><mi>n</mi></mrow></msup></math></span> for regions of large volume and we improve on previous estimates of lower bounds for the isoperimetric profiles of <span><math><msup><mrow><mi>S</mi></mrow><mrow><mn>2</mn></mrow></msup><mo>×</mo><msup><mrow><mi>R</mi></mrow><mrow><mn>2</mn></mrow></msup></math></span>, <span><math><msup><mrow><mi>S</mi></mrow><mrow><mn>3</mn></mrow></msup><mo>×</mo><msup><mrow><mi>R</mi></mrow><mrow><mn>2</mn></mrow></msup></math></span>, <span><math><msup><mrow><mi>S</mi></mrow><mrow><mn>2</mn></mrow></msup><mo>×</mo><msup><mrow><mi>R</mi></mrow><mrow><mn>3</mn></mrow></msup></math></span>. We also discuss some applications of these results in order to improve known lower bounds for the Yamabe invariant of certain product manifolds.</p></div>","PeriodicalId":51010,"journal":{"name":"Differential Geometry and its Applications","volume":"91 ","pages":"Article 102069"},"PeriodicalIF":0.5,"publicationDate":"2023-10-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49749805","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":"Classification of semi-parallel hypersurfaces of the product of two spheres","authors":"Shujie Zhai , Cheng Xing","doi":"10.1016/j.difgeo.2023.102067","DOIUrl":"https://doi.org/10.1016/j.difgeo.2023.102067","url":null,"abstract":"<div><p>It is known that Mendonça and Tojeiro (2013) <span>[19]</span> have established a complete classification of parallel submanifolds in the product manifold <span><math><msubsup><mrow><mi>Q</mi></mrow><mrow><msub><mrow><mi>k</mi></mrow><mrow><mn>1</mn></mrow></msub></mrow><mrow><msub><mrow><mi>n</mi></mrow><mrow><mn>1</mn></mrow></msub></mrow></msubsup><mo>×</mo><msubsup><mrow><mi>Q</mi></mrow><mrow><msub><mrow><mi>k</mi></mrow><mrow><mn>2</mn></mrow></msub></mrow><mrow><msub><mrow><mi>n</mi></mrow><mrow><mn>2</mn></mrow></msub></mrow></msubsup></math></span>, where <span><math><msubsup><mrow><mi>Q</mi></mrow><mrow><msub><mrow><mi>k</mi></mrow><mrow><mn>1</mn></mrow></msub></mrow><mrow><msub><mrow><mi>n</mi></mrow><mrow><mn>1</mn></mrow></msub></mrow></msubsup></math></span> (resp. <span><math><msubsup><mrow><mi>Q</mi></mrow><mrow><msub><mrow><mi>k</mi></mrow><mrow><mn>2</mn></mrow></msub></mrow><mrow><msub><mrow><mi>n</mi></mrow><mrow><mn>2</mn></mrow></msub></mrow></msubsup></math></span>) is an <span><math><msub><mrow><mi>n</mi></mrow><mrow><mn>1</mn></mrow></msub></math></span>-dimensional (resp. <span><math><msub><mrow><mi>n</mi></mrow><mrow><mn>2</mn></mrow></msub></math></span>-dimensional) real space form with constant curvature <span><math><msub><mrow><mi>k</mi></mrow><mrow><mn>1</mn></mrow></msub></math></span> (resp. <span><math><msub><mrow><mi>k</mi></mrow><mrow><mn>2</mn></mrow></msub></math></span>). In this paper, motivated by this result with considering further generalization, we study those semi-parallel hypersurfaces in case <span><math><msubsup><mrow><mi>Q</mi></mrow><mrow><msub><mrow><mi>k</mi></mrow><mrow><mn>1</mn></mrow></msub></mrow><mrow><msub><mrow><mi>n</mi></mrow><mrow><mn>1</mn></mrow></msub></mrow></msubsup><mo>=</mo><msubsup><mrow><mi>S</mi></mrow><mrow><msub><mrow><mi>k</mi></mrow><mrow><mn>1</mn></mrow></msub></mrow><mrow><msub><mrow><mi>n</mi></mrow><mrow><mn>1</mn></mrow></msub></mrow></msubsup></math></span> and <span><math><msubsup><mrow><mi>Q</mi></mrow><mrow><msub><mrow><mi>k</mi></mrow><mrow><mn>2</mn></mrow></msub></mrow><mrow><msub><mrow><mi>n</mi></mrow><mrow><mn>2</mn></mrow></msub></mrow></msubsup><mo>=</mo><msubsup><mrow><mi>S</mi></mrow><mrow><msub><mrow><mi>k</mi></mrow><mrow><mn>2</mn></mrow></msub></mrow><mrow><msub><mrow><mi>n</mi></mrow><mrow><mn>2</mn></mrow></msub></mrow></msubsup></math></span> with <span><math><msub><mrow><mi>k</mi></mrow><mrow><mn>1</mn></mrow></msub><mo>,</mo><msub><mrow><mi>k</mi></mrow><mrow><mn>2</mn></mrow></msub><mo>></mo><mn>0</mn></math></span>. As the main result, we classify semi-parallel hypersurfaces of <span><math><msubsup><mrow><mi>S</mi></mrow><mrow><msub><mrow><mi>k</mi></mrow><mrow><mn>1</mn></mrow></msub></mrow><mrow><msub><mrow><mi>n</mi></mrow><mrow><mn>1</mn></mrow></msub></mrow></msubsup><mo>×</mo><msubsup><mrow><mi>S</mi></mrow><mrow><msub><mrow><mi>k</mi></mrow><mrow><mn>2</mn></mrow></msub></mrow><mrow><msub><mrow><mi>n</mi></mrow><mrow><m","PeriodicalId":51010,"journal":{"name":"Differential Geometry and its Applications","volume":"91 ","pages":"Article 102067"},"PeriodicalIF":0.5,"publicationDate":"2023-10-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49749638","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":"Gronwall's conjecture for 3-webs with two pencils of lines","authors":"Sergey I. Agafonov","doi":"10.1016/j.difgeo.2023.102071","DOIUrl":"https://doi.org/10.1016/j.difgeo.2023.102071","url":null,"abstract":"<div><p>We prove the old-standing Gronwall conjecture in the particular case of linear 3-webs whose 2 foliations are 2 pencils of lines. For a non-hexagonal 3-web, we also introduce a family of projective torsion-free Cartan connections, the web leaves being geodesics for each member of the family, and give a web linearization criterion.</p></div>","PeriodicalId":51010,"journal":{"name":"Differential Geometry and its Applications","volume":"91 ","pages":"Article 102071"},"PeriodicalIF":0.5,"publicationDate":"2023-10-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49749800","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":"Pseudo-Conformal actions of the Möbius group","authors":"M. Belraouti , M. Deffaf , Y. Raffed , A. Zeghib","doi":"10.1016/j.difgeo.2023.102070","DOIUrl":"https://doi.org/10.1016/j.difgeo.2023.102070","url":null,"abstract":"<div><p>We study compact connected pseudo-Riemannian manifolds <span><math><mo>(</mo><mi>M</mi><mo>,</mo><mi>g</mi><mo>)</mo></math></span> on which the conformal group <span><math><mi>Conf</mi><mo>(</mo><mi>M</mi><mo>,</mo><mi>g</mi><mo>)</mo></math></span> acts essentially and transitively. We prove, in particular, that if the non-compact semi-simple part of <span><math><mi>Conf</mi><mo>(</mo><mi>M</mi><mo>,</mo><mi>g</mi><mo>)</mo></math></span> is the Möbius group, then <span><math><mo>(</mo><mi>M</mi><mo>,</mo><mi>g</mi><mo>)</mo></math></span> is conformally flat.</p></div>","PeriodicalId":51010,"journal":{"name":"Differential Geometry and its Applications","volume":"91 ","pages":"Article 102070"},"PeriodicalIF":0.5,"publicationDate":"2023-10-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49758929","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":"Geometry and topology of manifolds with integral radial curvature bounds","authors":"Jing Mao","doi":"10.1016/j.difgeo.2023.102064","DOIUrl":"https://doi.org/10.1016/j.difgeo.2023.102064","url":null,"abstract":"<div><p>In this paper, we systematically investigate the geometry and topology of manifolds with integral <em>radial</em> curvature bounds, and obtain many interesting and important conclusions.</p></div>","PeriodicalId":51010,"journal":{"name":"Differential Geometry and its Applications","volume":"91 ","pages":"Article 102064"},"PeriodicalIF":0.5,"publicationDate":"2023-10-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49749636","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":"Time analyticity for the parabolic type Schrödinger equation on Riemannian manifold with integral Ricci curvature condition","authors":"Wen Wang","doi":"10.1016/j.difgeo.2023.102045","DOIUrl":"10.1016/j.difgeo.2023.102045","url":null,"abstract":"<div><p>In the paper, we investigate the pointwise time analyticity of the parabolic type Schrödinger equation on a complete Riemannian manifold with integral Ricci curvature condition.</p></div>","PeriodicalId":51010,"journal":{"name":"Differential Geometry and its Applications","volume":"90 ","pages":"Article 102045"},"PeriodicalIF":0.5,"publicationDate":"2023-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47156979","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}