The piece family after a blow-up realises the transformed boundary #
The piece family after the blow-up of a centre realises the total transform of the boundary family,
that is, the strict transforms of the members in their old order followed by the exceptional divisor
π⁻¹(Z) as the last member ([Kol07, Definition 65]), through the label embedding extended by the
exceptional member (extendEmb). An old member's strict transform is the union of the strict
transforms of its pieces (the strict transform of a finite union is the union of the strict
transforms), the exceptional divisor is the union of the new pieces (one per face of the centre,
the preimages of the loci), the members off the range are empty, and pieces with the same label
stay pairwise disjoint: strict transforms of disjoint pieces lie over disjoint pieces, and the new
pieces lie over the disjoint loci of the faces of the centre.
The strict transform of a finite union is the union of the strict transforms.
Strict transforms of disjoint closed sets are disjoint.
The pieces of the transported family with an old label are the old pieces with that label.
The pieces with the new label are exactly the new pieces.
The union of the new pieces is the exceptional divisor.
The family after the blow-up of a centre realises the total transform of the boundary family through the extended label embedding ([Kol07, Definition 65]: the strict transforms of the members in the old order, the exceptional divisor last).