Exotic branes and non-geometric fluxes

We present and study ten-dimensional effective actions for various nongeometric fluxes of which exotic branes act as the magnetic sources. Each theory can be regarded as a U -dual version of the β -supergravity, a reformulation of the ten-dimensional supergravity which is suitable for describing non-geometric backgrounds with Q -flux. In each theory, we find a solution that corresponds to the background of an exotic brane and show that it is single-valued up to a gauge transformation, although the same background written in the standard background fields is not single-valued in a usual sense. Further, we also find a solution which corresponds to the background of an instanton that is the electric dual of the exotic brane and discuss its properties