%0 Conference Paper %F Oral %T Twistors, black holes and modularity %+ Laboratoire Charles Coulomb (L2C) %A Alexandrov, Sergey %F Invité %< sans comité de lecture %Z L2C:19-160 %B Twistors and Loops Meeting in Marseille %C Marseille, France %8 2019-09-02 %D 2019 %Z Physics [physics]/High Energy Physics - Theory [hep-th]Conference papers %X I'll show how twistorial description of quaternionic geometries combined with string theory dualities helped to solve a long standing mathematical problem - to understand modular properties of indefinite theta series. Then I'll use the solution of this problem to describe the modular behavior of the generatingfunction of degeneracies of BPS black holes appearing in Calabi-Yau compactifications of string theory. %G English %L hal-02285107 %U https://hal.science/hal-02285107 %~ CNRS %~ L2C %~ MIPS %~ UNIV-MONTPELLIER %~ UM-2015-2021