Key research themes
1. What are the implications of unstructured hardness assumptions for separating classes P and NP ∩ coNP?
This theme investigates whether and how the presence of unstructured hard problems within the intersection of NP and coNP can provide evidence towards separating P from NP ∩ coNP, focusing on constructions based on cryptographic assumptions and random oracles. It matters because unstructured hardness instances (as opposed to highly structured ones) offer a less assumption-heavy foundation for complexity separations, potentially advancing our understanding of class relations and cryptographic primitives.
2. How do reductions characterize the completeness and separations within NP, especially relating stronger reduction types to classical completeness notions?
Research here focuses on the landscape of reductions defining NP-completeness, investigating if certain reduction types (adaptive, nondeterministic, length-increasing) yield strictly more powerful completeness notions than classical polynomial-time many-one reductions. Understanding these relationships matters for clarifying the structure of NP-complete problems and the subtleties in completeness under different computational models, impacting both theory and applications of complexity.
3. What insights can empirical hardness models provide about the average-case difficulty of NP-complete problems beyond worst-case complexity?
This theme explores statistical and machine learning approaches to understanding how algorithm runtimes vary on NP-complete problem instances drawn from various distributions. Moving beyond worst-case analysis, empirical hardness models (EHMs) aim to predict runtime based on instance features, revealing practical tractability patterns, phase transitions in difficulty, and aiding algorithm selection and tuning. This research matters because it bridges theoretical complexity and applied performance, informing both algorithm design and theoretical understanding.