Cohomogeneity one manifolds with positive euler characteristic

We classify those manifolds of positive euler characteristic on which a lie group G acts with cohomogeneity one, where G is classical simpl

Do risk attitudes differ within the group of entrepreneurs?

The notion of risk and entrepreneurship has been widely discussed in the entrepreneurship literature. Starting a business involves risk and requires a risk-taking attitude. Most studies have com-pared entrepreneurs with non-entrepreneurs such as managers or bankers. So far, little research exists on the risk attitudes of different types of entrepreneurs. This study aims to fill this gap. Our particular focus is on the entrepreneurs’ motivations to start their business. The results show that opportunity entrepreneurs are more willing to take risks than necessity entrepreneurs. In addition, entrepreneurs who are motivated by creativity are more risk-tolerant than other entrepreneurs. The study contributes to the literature about risk attitudes of entrepreneurs and to the literature about necessity and opportunity entrepreneurship.Entrepreneurship; Self-employment; Risk attitude; Necessity entrepreneurship; Creativity entrepreneurship

The isomorphism problem for tree-automatic ordinals with addition

This paper studies tree-automatic ordinals (or equivalently, well-founded linearly ordered sets) together with the ordinal addition operation +. Informally, these are ordinals such that their elements are coded by finite trees for which the linear order relation of the ordinal and the ordinal addition operation can be determined by tree automata. We describe an algorithm that, given two tree-automatic ordinals with the ordinal addition operation, decides if the ordinals are isomorphic

Higher-dimensional Wannier interpolation for the modern theory of the Dzyaloshinskii-Moriya interaction: Application to Co-based trilayers

We present an advanced first-principles formalism to evaluate the Dzyaloshinskii-Moriya interaction (DMI) in its modern theory as well as Berry curvatures in complex spaces based on a higher-dimensional Wannier interpolation. Our method is applied to the Co-based trilayer systems Ir$_\delta$Pt$_{1-\delta}$/Co/Pt and Au$_\gamma$Pt$_{1-\gamma}$/Co/Pt, where we gain insights into the correlations between the electronic structure and the DMI, and we uncover prominent sign changes of the chiral interaction with the overlayer composition. Beyond the discussed phenomena, the scope of applications of our Wannier-based scheme is particularly broad as it is ideally suited to study efficiently the Hamiltonian evolution under the slow variation of very general parameters.Comment: 8 pages, 3 figures, contribution to Special Topics "New ab initio approaches to explore emergent phenomena in quantum matters" in J. Phys. Soc. Jp