Euclidean Distance degrees of real algebraic groups
  We study the problem of finding, in a real algebraic matrix group, the matrix closest to a given data matrix. We do so from the algebro-geometric perspective of Euclidean distance degrees. We recover several classical results; and among the new results that we prove is a formula for the Euclidean distance degree of special linear groups. 
Jasmijn A. Baaijens and Jan Draisma
math.OC math.AG