6.6.3 Referring to Definition 6.3, prove that (a) A totally bounded metric space is bounded (b)...
A metric space (X, d) is totally bounded if, given
ε>0, there exists a finite subset =
of X, called an ε-net, such that for each x∈X there
exists
∈
such that d(x,)
< ε. Prove that if Y is a subset of a totally bounded space X
then, given ε>0, the subset Y has an ε-net and
therefore Y is also totally bounded.
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Using only the definition of compact sets in a metric space, give examples of: (a) A nonempty bounded set in (R", dp), for n > 2 and 1 < pく00, which is not compact. (b) A bounded subset Y of R such that (Y, dy) contains nonempty closed and bounded subsets which are not compact (here dy is the metric inherited from the usual metric in R)
Using only the definition of compact sets in a metric space, give examples...
Part 2: Metrics and Norms 1. Norms and convergence: (a) Prove the l2 metric defined in class is a valid norm on R2 (b) Prove that in R2, any open ball in 12 ("Euclidean metric") can be enclosed in an open ball in the loo norm ("sup" norm). (c). Say I have a collection of functions f:I R. Say I (1,2). Consider the convergence of a sequence of functions fn (z) → f(x) in 12-Show that the convergence amounts to...
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...
In this problem we show that any metric space (X, d) is homeomorphic to a bounded metric space. (a) Define ρ : X X R by Show that ρ defines a metric on X. Conclude that (X,p) is a bounded metric space. (b) Show that f : (X, d) → (X, p) given by f(x) = x is a homeomorphism ism. (c) Is it true that if (X, d) is complete then (X, ρ) is complete?
In this problem we...
1. If A CB CM, and if B is totally bounded, show that A is totally bounded. 2. Show that a subset A of R is totally bounded if and only if it is bounded. In particular, if I is a closed, bounded, interval in R and ε > 0, show that I can be covered by finitely many closed subintervals J1, ..., Jn, each of length at most 8. 3. Is total boundedness preserved by homeomorphisms? Explain. (Hint: R...
8) Prove that C([O, 1]) is a metric space with the metric .1 d(f, g) = / If(x)-g(x)| dx. 9) Let (X, di) and (Y, d2) be metric spaces. a) Prove that X × Y is a metric space with the metric b) Prove that X x Y is a metric space with the metric
Topology
3. Either prove or disprove each of the following statements: (a) If d and p map (X, d) X, then the identity topologically equivalent metrics (X, p) and its inverse are both continuous are two on (b) Any totally bounded metric space is compact. (c) The open interval (-r/2, n/2) is homeomorphic to R (d) If X and Y are homeomorphic metric spaces, then X is complete if and only if Y is complete (e) Let X and Y...
(TOPOLOGY) Prove the following using the defintion:
Exercise 56. Let (M, d) be a metric space and let k be a positive real number. We have shown that the function dk defined by dx(x, y) = kd(x,y) is a metric on M. Let Me denote M with metric d and let M denote M with metric dk. 1. Let f: Md+Mk be defined by f(x) = r. Show that f is continuous. 2. Let g: Mx + Md be defined...
B2. (a) Let I denote the interval 0,1 and let C denote the space of continuous functions I-R. Define dsup(f,g)-sup |f(t)-g(t) and di(f.g)f (t)- g(t)ldt (f,g E C) tEI (i) Prove that dsup is a metric on C (ii) Prove that di is a metric on C. (You may use any standard properties of continuous functions and integrals, provided you make your reasoning clear.) 6 i) Let 1 denote the constant function on I with value 1. Give an explicit...