\contentsline {mtchap}{\numberline {2}Combinatorics}{565} \contentsline {mtsec}{\numberline {2.1}Final Elements in The Weyl Group}{565} \contentsline {mtsec}{\numberline {2.2}Final Types and Young Diagrams}{567} \contentsline {mtsec}{\numberline {2.3}Canonical Types}{572} \contentsline {mtsec}{\numberline {2.4}Admissible Elements}{575} \contentsline {mtsec}{\numberline {2.5}Shuffles}{576} \contentsline {mtchap}{\numberline {3}The Flag Space}{578} \contentsline {mtsec}{\numberline {3.1}The Flag space of the Hodge bundle}{578} \contentsline {mtsec}{\numberline {3.2}The canonical flag of an abelian variety}{580} \contentsline {mtchap}{\numberline {4}Strata on the Flag Space}{582} \contentsline {mtsec}{\numberline {4.1}The Stratification}{582} \contentsline {mtsec}{\numberline {4.2}Some Important Strata}{583} \contentsline {mtsec}{\numberline {4.3}Shuffling flags}{588} \contentsline {mtsec}{\numberline {4.4}The E-O strata on ${{\@mathcal A}}_g \otimes {\@mathbb F}_p$}{591} \contentsline {mtchap}{\numberline {5}Extension to the boundary}{591} \contentsline {mtchap}{\numberline {6}Existence of boundary components}{593} \contentsline {mtchap}{\numberline {7}Superspecial fibres}{594} \contentsline {mtchap}{\numberline {8}Local structure of strata}{598} \contentsline {mtsec}{\numberline {8.1}Stratified Spaces}{598} \contentsline {mtsec}{\numberline {8.2}Height $1$-Maps}{598} \contentsline {mtchap}{\numberline {9}Punctual flag spaces}{601} \contentsline {mtchap}{\numberline {10}Pieri formulas}{606} \contentsline {mtchap}{\numberline {11}Irreducibility properties}{611} \contentsline {mtchap}{\numberline {12}The Cycle Classes}{614} \contentsline {mtsec}{\numberline {12.1}Fulton's formulas}{615} \contentsline {mtsec}{\numberline {12.2}The $p$-rank strata}{617} \contentsline {mtsec}{\numberline {12.3}The $a$-number Strata}{619} \contentsline {mtsec}{\numberline {12.4}Positivity of tautological classes}{621} \contentsline {mtchap}{\numberline {13}Tautological rings}{621} \contentsline {mtchap}{\numberline {14}Comparison with ${\@mathcal S}(g,p)$}{625} \contentsline {mtchap}{\numberline {15}Appendix $g=3,4$}{626} \contentsline {mtsec}{\numberline {15.1}Admissible Strata for $g=3$}{626} \contentsline {mtsec}{\numberline {15.2}E-O Cycle Classes for $g=3$}{626} \contentsline {mtsec}{\numberline {15.3}E-O Cycle Classes for $g=4$}{627} \contentsline {mtchap}{References}{627}