Expanded degenerations and pairs
  Since Jun Li's original definition, several other definitions of expanded pairs and expanded degenerations have appeared in the literature. We explain how these definitions are related and introduce several new variants and perspectives. Among these are the twisted expansions used by Abramovich and Fantechi as a basis for orbifold techniques in degeneation formulas. 
Dan Abramovich, Charles Cadman, Barbara Fantechi, Jonathan Wise
math.AG