Compactness, Local Compactness, Completeness
Clearly, every compact metric space is locally compact. I always get confused when completeness is introduced into the picture. Which of the following are true? What are some easy counterexamples to those statements that are false?
- Every complete metric space is compact.
- Every complete metric space is locally compact.
- Every compact metric space is complete.
- Every locally compact metric space is complete.
- Every locally compact inner product space is of finite dimension.
False: the real line with the usual metric is a counterexample.
False: the irrationals are completely metrizable and nowhere locally compact.
True: a metric space is compact iff it is complete and totally bounded.
False: $(0,1)$ with the usual metric is a counterexample.
True; see this question and this question.