CatDat

category of metric spaces with ∞ allowed

  • notation: Met\mathbf{Met}_{\infty}
  • objects: metric spaces, where the metric is allowed to assume the value \infty
  • morphisms: non-expansive maps ff, meaning d(f(x),f(y))d(x,y)d(f(x),f(y)) \leq d(x,y) for all x,yx,y
  • Related categories: Metc\mathbf{Met}_cMet\mathbf{Met}
  • nLab Link

The fact that we allow \infty means that universal constructions work much better.

Satisfied Properties

Properties from the database

Deduced properties

Unsatisfied Properties

Properties from the database

Deduced properties*

*This also uses the deduced satisfied properties.

Unknown properties

There are 3 properties for which the database doesn't have an answer if they are satisfied or not. Please help to contribute the data!

Special objects

  • terminal object: singleton space
  • initial object: empty metric space
  • products: direct products with the metric d(x,y)=supidi(xi,yi)d(x,y) = \sup_i d_i(x_i,y_i)
  • coproducts: disjoint union with the metric that extends the given ones and gives points in different spaces the distance \infty

Special morphisms

  • isomorphisms: bijective isometries
  • monomorphisms: injective non-expansive maps
  • epimorphisms: non-expansive maps with dense image
  • regular monomorphisms:
  • regular epimorphisms: