scholarly journals Examples of compact Einstein four-manifolds with negative curvature

2020 ◽  
Vol 33 (4) ◽  
pp. 991-1038
Author(s):  
Joel Fine ◽  
Bruno Premoselli
Author(s):  
Dusa McDuff ◽  
Dietmar Salamon

This chapter examines various ways to construct symplectic manifolds and submanifolds. It begins by studying blowing up and down in both the complex and the symplectic contexts. The next section is devoted to a discussion of fibre connected sums and describes Gompf’s construction of symplectic four-manifolds with arbitrary fundamental group. The chapter also contains an exposition of Gromov’s telescope construction, which shows that for open manifolds the h-principle rules and the inclusion of the space of symplectic forms into the space of nondegenerate 2-forms is a homotopy equivalence. The final section outlines Donaldson’s construction of codimension two symplectic submanifolds and explains the associated decompositions of the ambient manifold.


Mathematics ◽  
2021 ◽  
Vol 9 (5) ◽  
pp. 531
Author(s):  
Pedro Pablo Ortega Palencia ◽  
Ruben Dario Ortiz Ortiz ◽  
Ana Magnolia Marin Ramirez

In this article, a simple expression for the center of mass of a system of material points in a two-dimensional surface of Gaussian constant negative curvature is given. By using the basic techniques of geometry, we obtained an expression in intrinsic coordinates, and we showed how this extends the definition for the Euclidean case. The argument is constructive and serves to define the center of mass of a system of particles on the one-dimensional hyperbolic sphere LR1.


1991 ◽  
Vol 103 (1) ◽  
pp. 471-495 ◽  
Author(s):  
K. D. Elworthy ◽  
Steven Rosenberg
Keyword(s):  

2015 ◽  
Vol 2016 (5) ◽  
pp. 1368-1386 ◽  
Author(s):  
Jérôme Bertrand ◽  
Benoît R. Kloeckner

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