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Regular Seminar Nikolaos Prezas (Bern University)
at: 12:00 room H503 abstract: | I will discuss recent progress in understanding non-geometric string backgrounds. These are inherently stringy constructions that are globally well- defined only up to T-dualities. One approach in analyzing such backgrounds is through the corresponding effective gauged supergravities. The classification of the latter in terms of embedding tensors provides us with a picture of the landscape of such backgrounds, realized in terms of non-geometric fluxes. Also, it is by now evident that a doubling of the coordinates of the underlying geometry is necessary for describing these backgrounds, since their stringy nature implies that winding modes should be treated on equal footing with the momentum modes. This leads us to doubled geometries and in particular twisted doubled tori, that are expected to underlie general supergravity gaugings. Of particular interest is the worldsheet description of such doubled geometries which involves chiral boson models. Although these models are not Lorentz invariant in general, for the twisted doubled tori Lorentz invariance is restored. Furthermore, the conditions for conformal invariance of those models agree with the conditions from minimizing the corresponding supergravity potential. This result firmly establishes that chiral boson models with twisted doubled tori target spaces are the worldsheet theories underlying a very broad class of supergravity gaugings. |