Stringy Origin of Discrete R-symmetries

Discrete symmetries play a crucial role in particle physics. They appear abundantly in string model constructions. We focus here on the case of discrete $R$-symmetries which are intrinsically connected to the Lorentz group in extra dimensions and the appearance of $N$-extended supersymmetry. In that sense, discrete $R$-symmetries can be understood as "fractionally" extended supersymmetry. These symmetries reveal insight about the location of fields in extra dimensions (in particular the Higgs boson). Applications can be found in the solution of the $\mu$-problem, suppression of proton decay and the structure of the soft terms of broken supersymmetry.Comment: Proceedings of the Corfu Summer Institute 2016 "School and Workshops on Elementary Particle Physics and Gravity",31 August - 23 September, 2016, Corfu, Greec

Ethnological approach of terrace farming

The vast distribution of terraces in the geographical Sudan zone of West Africa leads to the question why and under which conditions an agrarian society might apply this particular form of farming. From an anthropologist's point of view it is essential to understand why farmers practise this form of farming and therefore try to explain the reason for it. The best way to gain insight is the description of terrace farming and when taking a closer look, we realize that farming is nowhere only an isolated agricultural activity

Anomalous U(1) gauge symmetries and heterotic-typeI/II string duality

Anomalous U(1) gauge symmetries can appear both in heterotic and type I string theories. In the heterotic case we find a single anomalous U(1), while in open string theories several such symmetries can appear. Nonetheless, there is a conjectured duality symmetry that might connect these two theories. We review the properties of anomalous gauge symmetries in various string theories as well as the status of this heterotic-type I/II duality. We also comment on the possible phenomenological applications of anomalous gauge symmetries in string theory.Comment: 7 pages, Latex, JHEP, Contribution to the Proceedings of TMR99, European Program Meeting on Quantum Aspects of Gauge Theories, Supersymmetry and Unification, Paris, September 199