A structure theorem for unions of complete intersections
  Using the connections among almost complete intersection schemes, arithmetically Gorenstein schemes and schemes that are union of complete intersections we give a structure theorem for arithmetically Cohen-Macaulay union of two complete intersections of codimension $2.$ We apply the results for computing Hilbert functions and graded Betti numbers for such schemes. 
Alfio Ragusa, Giuseppe Zappala
math.AG math.AC