Does Merge Form a Hopf Algebra? Coproducts, Traces, and the Prospects of Algebraic Minimalism

원문 초록

Marcolli, Chomsky, and Berwick (2025; henceforth MCB) formulate the Merge operation of Minimalism on a Hopf algebra of Connes-Kreimer type, and claim that language and physics obey the same algebraic structure. This paper separates their program into the working hypothesis H, that Merge on workspaces can be described as a Hopf algebra, and the claim P placed on top of it, that language and physics obey the same principle, and examines the validity of H. MCB employs two coproducts in formulating Merge, corresponding to two different translations of movement (Internal Merge): $\Delta_d$, which deletes the lower copy, and $\Delta_c$, which leaves a trace. MCB uses the former in syntax and the latter at the syntax-semantics interface, but $\Delta_d$ is not coassociative, and $\Delta_c$ is not connected under the gradings MCB gives and, moreover, not coassociative as long as the labels of traces are retained. Consequently, MCB's algebra is not a Hopf algebra, and the Birkhoff factorization is not a consequence of the Hopf-algebra theorem but of a weaker statement that requires neither coassociativity nor connectedness. There are four ways to recover a Hopf algebra, but none of them can distinguish different traces, and hence none is compatible with Heim-Kratzer-style formal semantics, which reads traces as indexed variables. Thus H does not hold at present, and under the current formulation, making Minimalism a Hopf algebra and preserving its connection with formal semantics are mutually exclusive. Finally, we indicate three directions in which algebraic Minimalism may proceed.