Let (X,A,μ) be a metric space. 4. Let A and B be two collections of subsets...
Let M be a ơ-algebra of subsets of X and P the set of finite measures on M. Prove that (a) d(μ, v) = supAEM |μ( A)-v(A)| defines a metric on P (b) (P, d) is complete. Let M be a ơ-algebra of subsets of X and P the set of finite measures on M. Prove that (a) d(μ, v) = supAEM |μ( A)-v(A)| defines a metric on P (b) (P, d) is complete.
1. Let (X, d) be a metric space, and U, V, W CX subsets of X. (a) (i) Define what it means for U to be open. (ii) Define what it means for V to be closed. (iii) Define what it means for W to be compact. (b) Prove that in a metric space a compact subset is closed.
4·Let A and B be non-empty subsets of a space X. Prove that A U B is disconnected if A n B)U(A nB) 0. Prove that X is connected if and only if for every pair of non-empty subsets A and B of X such that X A U B we have (A B)U (An B)O.
In the following, (X,d) is an arbitrary metric space and (X,d,μ) is an arbitrary metric measure space. (6) Recall the definition of bounded set: The set A C (X, d) is bounded if δ(A) < 00 where 6(A)p d(a,a). (X,d) with ACBand B is bounded then A is bounded (a) Show that if A, B (b) Fix a set A. I B - (r), a single point, show that D(A, B)-0 if and only f (c) Prove that the function...
Q3 * You are given two subsets A, B C M of a metric space M. Define p by p=inf{d(x, y)| 2 € A, Y E B}. Prove that, if p > 0 then A and B are separated. Give an example where p=0, but A and B are not separated. Q4 Show that Q as a subset of R is disconnected. Likewise show R Q is disconnected.
(a) Suppose K is a compact subset of a metric space (X, d) and x є X but x K Show that there exist disjoint, open subsets of Gi and G2 of (X, d) such that r E Gi and KG2. (Hint: Use the version of compactness we called "having a compact topology." You will also need the Hausdorff property.) b) Now suppose that Ki and K2 are two compact, disjoint subsets of a metric space (X, d). Use (a)...
(a) Let (X, d) be a metric space. Prove that the complement of any finite set F C X is open. Note: The empty set is open. (b) Let X be a set containing infinitely many elements, and let d be a metric on X. Prove that X contains an open set U such that U and its complement UC = X\U are both infinite.
4. Let Uαα∈A be a finite open cover of a compact metric space X. For question for (a), (b) Remark: ε is called a Lebesgue number of the cover. (a) Show that there exists ε>0 such that for each x∈X, the open ball B(x;ε) is contained in one of the Uα’s. (b) Show that if at least one of the Uα’s is a proper subset of X, then there is a largest Lebesgue number for the cover. 4. Let {U}aea...
Let (X, d) be a discrete space and let (Y, d′) be any metric space. Prove that any function f : (X, d) → (Y, d′) is continuous. (Namely, any function from a discrete space to any metric space is continuous.)
5. Let X be a topological space and let A and B be connected subsets of X. Prove that if AndB+, then AUB is connected.