17 Answers votes newest views recent 18Why is an injective quasi-coherent sheaf’s restriction to an open subset still an injective object? 16Where does the splitting principle come from and does it generalize 12Interdependence between A^1 homotopy theory and algebraic cobordism 11In what topology DM stacks are stacks 11Algebraic de Rham cohomology vs. analytic de Rham cohomology 9Extraordinary cohomology as a derived functor? 8Derived categories of (coherent) sheaves of modules: exceptional images, gluing, and proper descent? 8Can Deligne-Mumford stacks be characterized by their restriction to a small subcategory? 8characterization of cofibrations in CW-complexes with G-action 7H-space structure on infinite projective spaces 6Gerbes for a cyclic group. (or maybe G_m too) 6Cyclic spaces and S^1-equivariant homotopy theory 6Flatness of relative canonical bundle 6Constructible sheaves and dg-modules 5Whitehead Products without Base Points? 4How ugly is the isomorphism R[GxH] = R[G] (X) R[H] for groups G, H? 3Proving interesting theorems about S_n using its character table.