2015/11/28 by Fernández, Marisa, Ivanov, Stefan, Muñoz, Vicente
#53C25 #55P62 #55S30 #Differential Geometry (math.DG) #FOS: Mathematics
paper · doi:10.48550/arxiv.1511.08930
We prove that any simply connected compact 3-Sasakian manifold, of dimension seven, is formal if and only if its second Betti number is b2<2. In the opposite, we show an example of a 7-dimensional Sasaki-Einstein manifold, with second Betti number b2≥ 2, which is formal. Therefore, such an example does not admit any 3-Sasakian structure. Examples of 7-dimensional simply connected compact formal Sasakian manifolds, with b2≥ 2, are also given.