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10.34 Claim . |
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Proof: Suppose by way of contradiction that some scientist M ApaEx*-identifies . We show that the existence of such an M implies that is Ex*-identifiable, contradicting Corollary 6.11. First, let p* be a program such that |
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Clearly, for each , we have that and . Hence, j p* is 1-conforming with each member of . Next, for each f, define |
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So, if , then . Also let r be a recursive function such that, for all i and j, j r(i)(j) = j i(min(Sj)). So if j i = f', for some , then j r(i) = f. Finally, let M' be a scientist such that, for each f, |
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As the reader may check, it follows from our assumption on M and the above definitions that M' must . Thus we have the desired contradiction. |
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10.35 Claim Suppose . Then . |
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Proof: Let p be a recursive function such that, for each s and x, |
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Also, let M be a scientist such that, for all s and s , M(s, s ) = p(s). |
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Fix some and suppose that s is such that j s is uniformly d-conforming to f. Then it easily follows that, for each j, , and hence, j p(s) = f. Therefore, M UapdEx-identifies f. |
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Let us contrast the preceding result with the following proposition, showing that Uap-type additional information cannot, in general, compensate for a higher density Ap-type additional information. The proof of this proposition is left to Exercise 10-18. |
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