CatDat

category of pseudo-metric spaces with non-expansive maps

  • notation: PMet\mathbf{PMet}
  • objects: pseudo-metric spaces
  • 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: Met\mathbf{Met}

In contrast to metric spaces, we do not demand d(x,y)=0    x=yd(x,y)=0 \implies x=y here.

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 8 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 pseudo-metric space
  • products: [finite case] direct products with the pseudo-metric d(x,y)=supidi(xi,yi)d(x,y) = \sup_i d_i(x_i,y_i)

Special morphisms

  • isomorphisms: bijective isometries
  • monomorphisms: injective non-expansive maps
  • epimorphisms: surjective non-expansive maps
  • regular monomorphisms:
  • regular epimorphisms: