Narrow Results

Compact symmetric spaces are probably one of the most prominent class of formal spaces, i.e. of spaces where the rational homotopy type is a formal consequence of the rational cohomology algebra. As a generalization, it is even known that their isotropy action is equivariantly formal. In this paper, we show that $({\mathbb{Z}}_2\oplus {\mathbb{Z}}_2)$-symmetric spaces are equivariantly formal and formal in the sense of Sullivan, in particular. Moreover, we give a short alternative proof of equivariant formality in the case of symmetric spaces with our new approach.

We give an up-to-date overview of geometric and topological properties of cosymplectic and coKähler manifolds. We also mention some of their applications to time-dependent mechanics.

The paper estimates the rates of return to investment in education in Egypt, allowing for multiple sources of heterogeneity across individuals. The paper finds that, in the period 1998–2006, returns to education increased for workers with higher education, but fell for workers with intermediate education levels; the relative wage of illiterate workers also fell in the period. This change can be explained by supply and demand factors. On the supply side, the number of workers with intermediate education, as well as illiterate ones, outpaced the growth of other categories joining the labor force during the decade. From the labor demand side, the Egyptian economy experienced a structural transformation by which sectors demanding higher-skilled labor expanded. In Egypt, individuals are sorted into different educational tracks, creating the first source of heterogeneity. Second, the paper finds that large-firm workers earn higher returns than small-firm workers. Third, females have larger returns to education. Formal workers earn higher rates of return to education than those in the informal sector, which did not happen a decade earlier. And finally, those individuals with access to technology (as proxied by personal computer ownership) have higher returns.

In a previous paper, the authors show some examples of compact symplectic solvmanifolds, of dimension six, which are cohomologically Kähler and they do not admit Kähler metrics because their fundamental groups cannot be the fundamental group of any compact Kähler manifold. Here we generalize such manifolds to higher dimension and, by using Auroux symplectic submanifolds [3], we construct four-dimensional symplectically aspherical manifolds with nontrivial π₂ and with no Kähler metrics.