Some general transfer principles for unit cost complexity problems are proved. As an application, we show that for infinite abelian groups \(\Sigma ^2 \cap \Pi ^2 \neq \Sigma ^1 \cup \Pi ^1\) . This has been shown for the group of real numbers by Herve Fournier and Pascal Koiran using the problem Twenty Questions. As this problem is not appropriate for infinite abelian groups in general, it was replaced here by Null-sack.

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The Path-bifurcation Hierarchy Does Not Collapse to \(\Sigma ^1\) in Infinite Abelian Groups

  • Mihai Prunescu

摘要

Some general transfer principles for unit cost complexity problems are proved. As an application, we show that for infinite abelian groups \(\Sigma ^2 \cap \Pi ^2 \neq \Sigma ^1 \cup \Pi ^1\) . This has been shown for the group of real numbers by Herve Fournier and Pascal Koiran using the problem Twenty Questions. As this problem is not appropriate for infinite abelian groups in general, it was replaced here by Null-sack.