E. W. Beth Dissertation Prize
Since 1998, FoLLI has been awarding the annual E. W. Beth Dissertation Prize for outstanding PhD dissertations in Logic, Language, and Information, with financial support of the E.W. Beth Foundation. The winners receive a certificate, a financial award of € 3,000 (possibly split between multiple winners), provided by the E. W. Beth Foundation, and an invitation to submit the dissertation for publication to the book series FoLLI-LNCS.
The 2026 prize went jointly to Adrienne Lancelot (PhD Paris 2025) and Keya Prakash (PhD Warwick 2025).
Adrienne Lancelot’s thesis Comparing Functional Programs, Or How to Put Lambda-terms Back in Order (Institut Polytechnique de Paris) makes fundamental contributions to the theory of program equivalence in the lambda calculus, addressing the challenge of reconciling semantic correctness with concerns of efficiency and cost. Through new results on contextual equivalence and call-by-value semantics, it advances our understanding of functional programming languages. Reviewers praised the thesis for its originality, mathematical rigor, and clarity, highlighting it as a landmark contribution to the field.
Keya Prakash’s thesis History-Deterministic Parity Automata: Games, Complexity, and the 2-Token Theorem (University of Warwick) makes major contributions to the theory of history-deterministic parity automata, resolving a central open problem concerning their characterization and its complexity. By proving the 2-token conjecture and developing new techniques for history-deterministic automata, it significantly advances the understanding of nondeterminism in automata theory. Reviewers praised the thesis for its innovative methods, exceptional clarity, and solution of a longstanding open problem, describing it as an outstanding contribution that will shape future research in the field.