SUMMARY
The space X = ℝ \ {a + b√2 : a, b ∈ ℚ} is not locally compact. The discussion references the Baire theorem, which states that in a locally compact Hausdorff space, the intersection of dense open sets is dense. While one participant initially questioned this, another clarified that the intersection of dense subsets is indeed dense in this context, drawing parallels to ℝ \ ℚ, which is completely metrizable. The key to proving non-local compactness lies in examining the canonical embedding i: X → ℝ and the properties of compact subsets.
PREREQUISITES
- Understanding of locally compact spaces in topology
- Familiarity with the Baire theorem
- Knowledge of dense sets and their properties
- Concept of compactness in metric spaces
NEXT STEPS
- Study the Baire theorem in detail and its implications for topological spaces
- Explore the properties of dense subsets in metric spaces
- Investigate canonical embeddings and their role in topology
- Learn about compactness and its characterization in different topological contexts
USEFUL FOR
Mathematicians, particularly those specializing in topology, graduate students studying advanced mathematical concepts, and anyone interested in the properties of locally compact spaces.