Lars Birkedal is a world leader in foundational programming languages research, and *the* pre-eminent researcher of his generation in the area of programming language semantics. His work, spanning a multitude of top journal and conference publications, has had significant impact in many areas. These include foundational type theory, compiler implementation, Milner's bigraphical reactive systems, logics and models for relational parametricity, and verification technology for semantically complex languages.
Birkedal is a pioneer in "bringing semantics into the 21st century":
developing rigorous and scalable semantic and verification techniques to account for the needs and complexities of modern languages. Toward this end in particular, he has (a) made numerous advances to the theory and practice of region-based memory management, (b) made fundamental contributions to the theory of relational parametricity, which underlies our semantic understanding of abstract data types, and (c) developed higher-order separation logics and other powerful tools for the modular verification of realistic imperative, object-oriented, and concurrent programming patterns.
In short, Birkedal has tackled hard problems of paramount importance to the future of programming language research, and has made startling advancements across the board. He has done so both independently, via the research group he built up at the IT University of Copenhagen, and also through fruitful collaborations with an impressive network of international colleagues, thus setting an excellent example for other junior researchers.