Some semilattices of definable sets in continuous logic #
JAMES E. HANSON
Definition 1.1 defines a topometric space.
In the ordering of topologies, ⊥ is the discrete topology and τ₀ ≤ τ₁ means τ₀ refines τ₁, i.e., τ₀ ⊇ τ₁.
Note that neither the trivial ⊤ or discrete ⊥ topology can be paired with the usual metric on ℝ to form a topometric space; so the notion is subtle. We merely prove that if we use the same topology as that obtained from the metric then we always have a topometric space.
Topometric space structure on X
.
- topology : TopologicalSpace X
- metric : MetricSpace X
- refines : UniformSpace.toTopologicalSpace ≤ TopometricSpace.topology
Instances
theorem
TopometricSpace.refines
{X : Type}
[self : TopometricSpace X]
:
UniformSpace.toTopologicalSpace ≤ TopometricSpace.topology
theorem
TopometricSpace.lowerSemiContinuous
{X : Type}
[self : TopometricSpace X]
(ε : ↑(Set.Ioi 0))
:
If we in particular let the topology be that obtained from the metric then we do have a topometric space.
Equations
- EasyTopometric X = { topology := UniformSpace.toTopologicalSpace, metric := m, refines := ⋯, lowerSemiContinuous := ⋯ }