- #1
santiagorf
- 2
- 0
My problem is that the space [itex] X= (0,1)[/itex] is not sequentially compact and compact at the same time.
It is not sequentially compact:
If we define the sequence [itex](\frac{1}{n}) [/itex] we can show that it is not sequentially compact as the sequence converges to 0, but [itex] 0 \notin X[/itex].
It is compact:
On the other hand, for X to be compact we need
1) bounded: The space X is bounded as any ball with center [itex] x \in X [/itex] and radius 2 will X.
2) closed: Is closed as its complement is the empty set (which is open)
Thus, the set [itex] X [/itex] is compact, which is a contradiction as X is not sequentially compact.
Where is my mistake when I show that X is compact?
It is not sequentially compact:
If we define the sequence [itex](\frac{1}{n}) [/itex] we can show that it is not sequentially compact as the sequence converges to 0, but [itex] 0 \notin X[/itex].
It is compact:
On the other hand, for X to be compact we need
1) bounded: The space X is bounded as any ball with center [itex] x \in X [/itex] and radius 2 will X.
2) closed: Is closed as its complement is the empty set (which is open)
Thus, the set [itex] X [/itex] is compact, which is a contradiction as X is not sequentially compact.
Where is my mistake when I show that X is compact?