VLDB 2026 Research / reviewers in the wild / expert
Christophe Marciot
dblp:409/6273
· DBLP profile ↗
2ranked-venue papers
0as first author
2since 2021 · last 2026
0009-0003-0831-5509ORCID · reported
Domains — the database's venue-derived domains; a paper can count in several
Theory of computation · 2 · 2 since 2021
| Year | Publication | Venue | Position |
|---|---|---|---|
| 2026 | Separations Above TFNP from Sherali-Adams Lower BoundsabstractUnlike in TFNP, for which there is an abundance of problems capturing natural existence principles which are incomparable (in the black-box setting), Kleinberg et al. [Robert Kleinberg et al., 2021] observed that many of the natural problems considered so far in the second level of the total function polynomial hierarchy (TFΣ₂) reduce to the Strong Avoid problem. In this work, we prove that the Linear Ordering Principle does not reduce to Strong Avoid in the black-box setting, exhibiting the first TFΣ₂ problem that lies outside of the class of problems reducible to Strong Avoid. The proof of our separation exploits a connection between total search problems in the polynomial hierarchy and proof complexity, recently developed by Fleming, Imrek, and Marciot [Fleming et al., 2025]. In particular, this implies that to show our separation, it suffices to show that there is no small proof of the Linear Ordering Principle in a Σ₂-variant of the Sherali-Adams proof system. To do so, we extend the classical pseudo-expectation method to the Σ₂ setting, showing that the existence of a Σ₂ pseudo-expectation precludes a Σ₂ Sherali-Adams proof. The main technical challenge is in proving the existence of such a pseudo-expectation, we manage to do so by solving a combinatorial covering problem about permutations. We also show that the extended pseudo-expectation bound implies that the Linear Ordering Principle cannot be reduced to any problem admitting a low-degree Sherali-Adams refutation. Noah Fleming, Anna Gál, Deniz Imrek, Christophe Marciot |
CCC | 4 |
| 2025 | Provably Total Functions in the Polynomial Hierarchy
Noah Fleming, Deniz Imrek, Christophe Marciot |
CCC | 3 |