scholarly journals Four-manifolds up to connected sum with complex projective planes

2022 ◽  
Vol 144 (1) ◽  
pp. 75-118
Author(s):  
Daniel Kasprowski ◽  
Mark Powell ◽  
Peter Teichner
Keyword(s):  
Projective Planes ◽  
Connected Sum ◽  
Four Manifolds ◽  
Complex Projective

scholarly journals FOUR-MANIFOLDS WITH POSITIVE CURVATURE

2020 ◽  
pp. 1-13
Author(s):  
R. DIÓGENES ◽  
E. RIBEIRO ◽  
E. RUFINO
Keyword(s):  
Riemannian Manifold ◽  
Compact Manifold ◽  
Positive Curvature ◽  
Conformally Flat ◽  
Complex Projective Plane ◽  
Connected Sum ◽  
Sectional Curvatures ◽  
Four Manifolds ◽  
Complex Projective ◽  
Flat Riemannian Manifold

Abstract In this note, we prove that a four-dimensional compact oriented half-conformally flat Riemannian manifold M 4 is topologically $\mathbb{S}^{4}$ or $\mathbb{C}\mathbb{P}^{2}$ , provided that the sectional curvatures all lie in the interval $\left[ {{{3\sqrt {3 - 5} } \over 4}, 1} \right]$ In addition, we use the notion of biorthogonal (sectional) curvature to obtain a pinching condition which guarantees that a four-dimensional compact manifold is homeomorphic to a connected sum of copies of the complex projective plane or the 4-sphere.

scholarly journals Real Hypersurfaces of Nonflat Complex Projective Planes Whose Jacobi Structure Operator Satisfies a Generalized Commutative Condition

2016 ◽  
Vol 2016 ◽  
pp. 1-6
Author(s):  
Theocharis Theofanidis
Keyword(s):  
Projective Plane ◽  
Projective Planes ◽  
Additional Restriction ◽  
Real Hypersurfaces ◽  
Specific Function ◽  
Complex Projective Plane ◽  
Jacobi Structure ◽  
Complex Projective

Real hypersurfaces satisfying the conditionϕl=lϕ(l=R(·,ξ)ξ)have been studied by many authors under at least one more condition, since the class of these hypersurfaces is quite tough to be classified. The aim of the present paper is the classification of real hypersurfaces in complex projective planeCP2satisfying a generalization ofϕl=lϕunder an additional restriction on a specific function.

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