RANDOMNESS NOTIONS AND REVERSE MATHEMATICS.
We investigate the strength of a randomness notion ${\cal R}$ as a set-existence principle in second-order arithmetic: for each Z there is an X that is ${\cal R}$ -random relative to Z. We show that the equivalence between 2-randomness and being infinitely often C -incompressible is provable in $...
| Published in: | Journal of Symbolic Logic Vol. 85; no. 1; pp. 271 - 300 |
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| Main Authors: | , |
| Format: | Article |
| Published: |
Cambridge University Press
Mar2020
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| Subjects: | |
| Online Access: | View this record in EBSCOhost |
| Summary: | We investigate the strength of a randomness notion ${\cal R}$ as a set-existence principle in second-order arithmetic: for each Z there is an X that is ${\cal R}$ -random relative to Z. We show that the equivalence between 2-randomness and being infinitely often C -incompressible is provable in $RC{A_0}$. We verify that $RC{A_0}$ proves the basic implications among randomness notions: 2-random $\Rightarrow$ weakly 2-random $\Rightarrow$ Martin-Löf random $\Rightarrow$ computably random $\Rightarrow$ Schnorr random. Also, over $RC{A_0}$ the existence of computable randoms is equivalent to the existence of Schnorr randoms. We show that the existence of balanced randoms is equivalent to the existence of Martin-Löf randoms, and we describe a sense in which this result is nearly optimal. |
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