\BOOKMARK [1][-]{section.1}{Elements of the geometry of K3 surfaces}{} \BOOKMARK [2][-]{subsection.1.1}{Definitions, key examples, and basic properties}{section.1} \BOOKMARK [2][-]{subsection.1.2}{Complex geometry}{section.1} \BOOKMARK [1][-]{section.2}{The Mori-Mukai argument}{} \BOOKMARK [1][-]{section.3}{Questions on rational curves}{} \BOOKMARK [2][-]{subsection.3.1}{Key conjectures}{section.3} \BOOKMARK [2][-]{subsection.3.2}{Rational curves on special K3 surfaces}{section.3} \BOOKMARK [1][-]{section.4}{K3 surfaces in positive characteristic}{} \BOOKMARK [2][-]{subsection.4.1}{What goes wrong in characteristic p?}{section.4} \BOOKMARK [2][-]{subsection.4.2}{What goes right in characteristic p?}{section.4} \BOOKMARK [2][-]{subsection.4.3}{Frobenius and the Weil conjectures}{section.4} \BOOKMARK [2][-]{subsection.4.4}{On the action of Frobenius}{section.4} \BOOKMARK [2][-]{subsection.4.5}{Tate conjecture for K3 surfaces}{section.4} \BOOKMARK [2][-]{subsection.4.6}{Reduction results}{section.4} \BOOKMARK [1][-]{section.5}{Evaluating the Picard group in practice}{} \BOOKMARK [1][-]{section.6}{Mori-Mukai in mixed characteristic}{}