Wednesday, 16 December 2015

general topology - Immediate succesors in [0,1)timesmathbbZ+ and mathbbZ+times[0,1)

I am working on one example from Munkres book "Topology"and I would like to clarify one question.



Example: Consider the set [0,1) of real numbers and the set Z+ of positive integers, both in their usual orders; give Z+×[0,1) the dictionary order. This set has the same order type as the set of nonnegative reals; the function f(n×t)=n+t1

is the required bijective order-preserving correspondence. On the other hand, the set [0,1)×Z+ in the dictionary order has quite a different order type; for example, every element of this ordered set has an immediate successor.



My questions:



1) I've checked that [0,1)×Z+ has the same order type as the set of nonnegative reals, right?




2) Any element (t,n) from [0,1)×Z+ has immediate successor, namely (t,n+1). Right?



3) But elements in Z+×[0,1) have not immediate successors, right?

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