2026/07/25 by Anwita Bhowmik, Salvatore Tringali
#math.NT #math.CO #math.GR #math.RA
Let H be a numerical monoid, that is, a cofinite submonoid of \mathbb N (the non-negative integers under addition). Denote by \mathcal Pfin,0(H) the monoid obtained by endowing the family of all finite subsets of H containing 0 with the operation of setwise addition induced by H on its power set. Tringali and Yan [JCTA, 2025] have recently established that \mathcal Pfin,0(\mathbb N) has a unique non-trivial automorphism, and conjectured that the automorphism group of \mathcal Pfin,0(H) is trivial whenever H ≠ \mathbb N. We prove this conjecture and, as a byproduct, give a new proof of the Tringali--Yan theorem.