Aspects of Muchnik's paradox in restricted betting

01/14/2022

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by   George Barmpalias, et al.

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Muchnik's paradox says that enumerable betting strategies are not always reducible to enumerable strategies whose bets are restricted to either even rounds or odd rounds. In other words, there are outcome sequences x where an effectively enumerable strategy succeeds, but no such parity-restricted effectively enumerable strategy does. We characterize the effective Hausdorff dimension of such x, showing that it can be as low as 1/2 but not less. We also show that such reals that are random with respect to parity-restricted effectively enumerable strategies with packing dimension as low as log√(3). Finally we exhibit Muchnik's paradox in the case of computable integer-valued strategies.