Co-c.e. spheres and cells in computable metric spaces
  We investigate conditions under which a co-computably enumerable set in a computable metric space is computable. Using higher-dimensional chains and spherical chains we prove that in each computable metric space which is locally computable each co-computably enumerable sphere is computable and each co-c.e. cell with co-c.e. boundary sphere is computable. 
Zvonko Iljazovic (University of Zagreb, Croatia)
cs.LO math.LO