Lambek's wrote
two short PhD theses on separate topics: one studying
quaternions in the foundations of mathematical physics (specifically the
biquaternion algebra containing
Minkowski space), and another on the problem of embedding a
semigroup into a
group. The second component, attacking a question that had been
previously addressed by
Anatoly Maltsev but using a novel geometric approach, was published by the
Canadian Journal of Mathematics. He later returned to
biquaternions when in 1995 he contributed "If Hamilton had prevailed: Quaternions in Physics", which exhibited the
Riemann–Silberstein bivector to express the free-space electromagnetic equations. Lambek supervised 17 doctoral students, and has 99 doctoral descendants as of 2025. He has over 100 publications listed in the
Mathematical Reviews, including 6 books. His earlier work was mostly in
module theory, especially torsion theories, non-commutative localization, and
injective modules. One of his earliest papers, , proved the
Lambek–Moser theorem about integer sequences. In 1963 he published an important result, now known as Lambek's theorem, on
character modules characterizing flatness of a module. His more recent work is in
pregroups and
formal languages; his earliest works in this field were probably and . He is noted, among other things, for the
Lambek calculus, an influential effort to capture mathematical aspects of natural language syntax in logical form by reducing
grammaticality to a test of logical entailment in a certain
sequent calculus, as well as for developing the connections between
typed lambda calculus and
cartesian closed categories (see
Curry–Howard–Lambek correspondence). His last works were on
pregroup grammar. == Selected works ==