scholarly journals Isoparametric Hypersurfaces with four Principal Curvatures Revisited

2009 ◽  
Vol 193 ◽  
pp. 129-154 ◽  
Author(s):  
Quo-Shin Chi
Keyword(s):  
Partial Differential Equations ◽  
Differential Equations ◽  
Fundamental Form ◽  
Isoparametric Hypersurface ◽  
Geometric Meaning ◽  
Principal Curvatures ◽  
Expansion Formula ◽  
Isoparametric Hypersurfaces ◽  
Focal Submanifold

AbstractThe classification of isoparametric hypersurfaces with four principal curvatures in spheres in [2] hinges on a crucial characterization, in terms of four sets of equations of the 2nd fundamental form tensors of a focal submanifold, of an isoparametric hypersurface of the type constructed by Ferus, Karcher and Münzner. The proof of the characterization in [2] is an extremely long calculation by exterior derivatives with remarkable cancellations, which is motivated by the idea that an isoparametric hypersurface is defined by an over-determined system of partial differential equations. Therefore, exterior differentiating sufficiently many times should gather us enough information for the conclusion. In spite of its elementary nature, the magnitude of the calculation and the surprisingly pleasant cancellations make it desirable to understand the underlying geometric principles.In this paper, we give a conceptual, and considerably shorter, proof of the characterization based on Ozeki and Takeuchi’s expansion formula for the Cartan-Münzner polynomial. Along the way the geometric meaning of these four sets of equations also becomes clear.

scholarly journals Classification of Möbius Isoparametric Hypersurfaces in 4

2005 ◽  
Vol 179 ◽  
pp. 147-162 ◽  
Author(s):  
Zejun Hu ◽  
Haizhong Li
Keyword(s):  
Fundamental Form ◽  
Second Fundamental Form ◽  
Isoparametric Hypersurface ◽  
Isoparametric Hypersurfaces ◽  
Möbius Form ◽  
Möbius Geometry ◽  
Dimensional Unit ◽  
Dupin Hypersurfaces ◽  
Möbius Second Fundamental Form

AbstractLet Mn be an immersed umbilic-free hypersurface in the (n + 1)-dimensional unit sphere n+1, then Mn is associated with a so-called Möbius metric g, a Möbius second fundamental form B and a Möbius form Φ which are invariants of Mn under the Möbius transformation group of n+1. A classical theorem of Möbius geometry states that Mn (n ≥ 3) is in fact characterized by g and B up to Möbius equivalence. A Möbius isoparametric hypersurface is defined by satisfying two conditions: (1) Φ ≡ 0; (2) All the eigenvalues of B with respect to g are constants. Note that Euclidean isoparametric hyper-surfaces are automatically Möbius isoparametric, whereas the latter are Dupin hypersurfaces.In this paper, we prove that a Möbius isoparametric hypersurface in 4 is either of parallel Möbius second fundamental form or Möbius equivalent to a tube of constant radius over a standard Veronese embedding of ℝP2 into 4. The classification of hypersurfaces in n+1 (n ≥ 2) with parallel Möbius second fundamental form has been accomplished in our previous paper [6]. The present result is a counterpart of Pinkall’s classification for Dupin hypersurfaces in 4 up to Lie equivalence.

scholarly journals PARA-BLASCHKE ISOPARAMETRIC HYPERSURFACES IN A UNIT SPHERE Sn + 1(1)

2012 ◽  
Vol 54 (3) ◽  
pp. 579-597 ◽  
Author(s):  
SHICHANG SHU ◽  
BIANPING SU
Keyword(s):  
Fundamental Form ◽  
Unit Sphere ◽  
Second Fundamental Form ◽  
Isoparametric Hypersurface ◽  
Principal Curvatures ◽  
Isoparametric Hypersurfaces ◽  
Blaschke Tensor ◽  
Blaschke Isoparametric Hypersurface ◽  
Full Classification ◽  
Möbius Second Fundamental Form

AbstractLet A = ρ2∑i,jAijθi ⊗ θj and B = ρ2∑i,jBij θi ⊗ θj be the Blaschke tensor and the Möbius second fundamental form of the immersion x. Let D = A + λB be the para-Blaschke tensor of x, where λ is a constant. If x: Mn ↦ Sn + 1(1) is an n-dimensional para-Blaschke isoparametric hypersurface in a unit sphere Sn + 1(1) and x has three distinct Blaschke eigenvalues one of which is simple or has three distinct Möbius principal curvatures one of which is simple, we obtain the full classification theorems of the hypersurface.

scholarly journals A Class of Special Hypersurfaces in Real Space Forms

2016 ◽  
Vol 2016 ◽  
pp. 1-6
Author(s):  
Yan Zhao ◽  
Ximin Liu
Keyword(s):  
Real Space ◽  
Principal Curvatures ◽  
Space Forms ◽  
Isoparametric Hypersurfaces ◽  
Real Space Forms ◽  
Constant Principal Curvatures

We define the generalized golden- and product-shaped hypersurfaces in real space forms. A hypersurfaceMin real space formsRn+1,Sn+1, andHn+1is isoparametric if it has constant principal curvatures. Based on the classification of isoparametric hypersurfaces, we obtain the whole families of the generalized golden- and product-shaped hypersurfaces in real space forms.

scholarly journals Classification of Exact Solutions for Generalized Form of Equation

2013 ◽  
Vol 2013 ◽  
pp. 1-11 ◽  
Author(s):  
Hasan Bulut
Keyword(s):  
Partial Differential Equations ◽  
Differential Equations ◽  
Exact Solutions ◽  
Nonlinear Partial Differential Equations ◽  
Generalized Equation ◽  
Polynomial Method ◽  
Partial Differential ◽  
Elliptic Solutions ◽  
Complete Discrimination System

The classification of exact solutions, including solitons and elliptic solutions, to the generalized equation by the complete discrimination system for polynomial method has been obtained. From here, we find some interesting results for nonlinear partial differential equations with generalized evolution.

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