On paraquaternionic submersions between paraquaternionic K\"ahler manifolds

In this paper we deal with some properties of a class of semi-Riemannian submersions between manifolds endowed with paraquaternionic structures, proving a result of non-existence of paraquaternionic submersions between paraquaternionic K\"ahler non locally hyper paraK\"ahler manifolds. Then we examine, as an example, the canonical projection of the tangent bundle, endowed with the Sasaki metric, of an almost paraquaternionic Hermitian manifold.Comment: 13 pages, no figure

Preliminary checklist of the Italian gypsophilous flora

The richness and uniqueness of the flora growing on gypsum substrates in Italy is known since the XIX century (Macchiati, 1888). Furthermore, the concept of plant gypsophily can be defined as the exclusiveness (or virtually exclusiveness) for living in gypsum outcropping rocks. Thus only those plant species, which show preference – or even exclusivity - for gypsum substrates, would be classified as gipsophilous (Mota et al., 2011). The main aim of this research has been the elaboration of a checklist of the Italian gypsophilous flora. The study was made possible through international collaboration between the "Mediterranea" University of Reggio Calabria (Italy) and the University of Almería (Spain). During the first step, an extensive literature review has been carried out in order to collect all available information about gypsophilous flora and to compile a preliminary list. Afterwards 18 regional botanists experts on Italian gypsum flora have been asked to rank the preference of these species for gypsum soils. Following the methodology proposed by Mota et al. (2009), the gypsophilous character of more than 100 plant species has been thus ranked on a scale ranging from 1 to 5 (with 5 representing for a total dependence on gypsum substrates). According to the obtained values, all the plant species, ranking between absolute or preferent gypsophytes, will figure in the final checklist of the gypsophytes of the whole Italian territory

Hidden symmetries and Killing tensors on curved spaces

Higher order symmetries corresponding to Killing tensors are investigated. The intimate relation between Killing-Yano tensors and non-standard supersymmetries is pointed out. In the Dirac theory on curved spaces, Killing-Yano tensors generate Dirac type operators involved in interesting algebraic structures as dynamical algebras or even infinite dimensional algebras or superalgebras. The general results are applied to space-times which appear in modern studies. One presents the infinite dimensional superalgebra of Dirac type operators on the 4-dimensional Euclidean Taub-NUT space that can be seen as a twisted loop algebra. The existence of the conformal Killing-Yano tensors is investigated for some spaces with mixed Sasakian structures.Comment: 12 pages; talk presented at Group 27 Colloquium, Yerevan, Armenia, August 200