Mihalis Petropoulos

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We study D-branes of the SL(2, R) WZW model, and of its discrete orb-ifolds. Gluing the currents by group automorphisms leads to three types of D-branes : two-dimensional hyperbolic planes (H 2), de Sitter branes (dS 2), or anti-de-Sitter branes (AdS 2). We explain that the dS 2 branes are unphysical, because the electric field on their worldvolume is(More)
Lately, recommendation systems have received significant attention. Most existing approaches though, recommend items of potential interest to users by completely ignoring the temporal aspects of ratings. In this paper, we argue that time-aware recommendations need to be pushed in the foreground. We introduce an extensive model for time-aware recommendations(More)
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