Open and Closed -- Tomas Transtromer

A background in mathematics gives my enchantment with words a special twist. Each time I see familiar math terms in a poem I layer their mathematical meanings amid their mainstream ones. Two such terms are "open" and "closed." (I'll supply brief mathematical explanation at the end of this post but, first, here is "Open and Closed Spaces" -- a poem by the winner of the 2011 Nobel prize  for Literature, Swedish poet Tomas Transtromer. )