TY - JOUR A1 - Enders, Jörg A1 - Müller, Reto A1 - Topping, Peter M. T1 - On Type-I singularities in Ricci flow JF - Communications in analysis and geometry N2 - We define several notions of singular set for Type-I Ricci flows and show that they all coincide. In order to do this, we prove that blow-ups around singular points converge to nontrivial gradient shrinking solitons, thus extending work of Naber [15]. As a by-product we conclude that the volume of a finite-volume singular set vanishes at the singular time. We also define a notion of density for Type-I Ricci flows and use it to prove a regularity theorem reminiscent of White's partial regularity result for mean curvature flow [22]. Y1 - 2011 SN - 1019-8385 VL - 19 IS - 5 SP - 905 EP - 922 PB - International Press of Boston CY - Somerville ER -