chapter  5
Presentations of reals
Pages 4

Previously we have seen that x has representations of degree L (x). However, presentations can behave quite differently.

We build a computable presentation 2“ ^ ° f a > v*a the nearly c.e. definition. That is, we have an approximation a = •ao,s • • • and obey the conditions that if aifS = 1 and aijS+\ = 0 then ajtS+\ becomes 1 for some j < i. To make a noncomputable, we must also meet the requirements:

The reader should think of this as a cautious investor wishing to sell off some shares, but not allowing the market to realize this, so they drip feed the shares into the market each time the price recovers.