1) Bad sign for a traveler 2) Hotel turndown
Found on
https://www.crosswordclues.com/clue/no-vacancy
The goal of algebraic topology is to categorize or classify topological spaces. Homotopy groups were invented in the late 19th century as a tool for such classification, in effect using the set of mappings from an n-sphere in to a space as a way to probe the structure of that space. An obvious question was how this new tool would work on n-spheres...
Found on
http://en.wikipedia.org/wiki/No_Vacancy
No exact match found.
