Dice Question Streamline Icon: https://streamlinehq.com

Existence of a TFΣ3^P problem not collapsing to TFNP with a Σ2^P oracle; further collapses for Empty and Short-Choice

Determine whether there exists a total search problem in TFΣ3^P that does not collapse to any TFNP subclass when given access to a Σ2^P oracle; additionally, ascertain whether the TFΣ2^P problems Empty and Short-Choice further collapse to smaller TFNP subclasses relative to appropriate oracles.

Information Square Streamline Icon: https://streamlinehq.com

Background

The paper develops a general framework showing collapses of problems in the total function hierarchy TFΣiP to TFNP subclasses equipped with Σ{i-1}P oracles. Several prominent TFΣ3P problems (e.g., King in this work; Shattering in prior work) collapse to smaller classes with Σ2P access.

This raises the question of whether any TFΣ3P problem resists such collapses. For TFΣ2P, only Empty and Short-Choice are highlighted as not yet known to collapse further. Understanding these boundaries would clarify the landscape of the total function hierarchy under oracle access.

References

Below we list a few open questions that arise from our work. Is there a candidate $\cc{TF\Sigma_3P}$ problem that does not collapse to a sub-class of \cc{TFNP} with access to a $\cc{\Sigma_2P}$ oracle? In the case of $\cc{TF\Sigma_2P}$ the only problems not known to collapse further down are #1{Empty} and #1{Short-Choice} . Do these problems also admit further collapses?

Downward self-reducibility in the total function polynomial hierarchy (2507.19108 - Gajulapalli et al., 25 Jul 2025) in Discussion and Open questions, Item 1