@misc{10498/40257,
year = {2026},
month = {9},
url = {http://hdl.handle.net/10498/40257},
abstract = {We introduce and study the family of super adaptable monoids, which includes, among many others, all conical refinement monoids that are either finitely generated, or countable, primely generated, and regular. Our main result shows that any countable super adaptable monoid can be realized by a von Neumann regular ring, thus answering affirmatively the Realization problem for this class. The result is new even for the subclass of countable, primely generated, regular conical refinement monoids, which we show can be realized by both a von Neumann regular ring and a purely infinite, real rank
zero C^*-algebra.

To prove this result, we develop a systematic framework that connects three fundamental structures: abstract monoids, separated graphs (a specific class of colored graphs), and von Neumann regular rings. By establishing functorial connections among these classes, we translate several algebraic properties of monoids into combinatorial and ring-theoretic notions. This allows us not only to prove the main realization result, but also to obtain several characterizations of super adaptable monoids. As a particular application, these can be used to provide a complete characterization of which regular monoids arise as
graph monoids.

To our knowledge, this work offers the first self-contained treatment in the literature where the complete realization process —from abstract monoids through I-systems and separated graphs to regular rings and C^∗-algebras— isdeveloped sequentially and in full detail within a single text.},
organization = {All authors were partially supported by MINECO (grant No. PID2023-147110NB-I00). PA and EV were also partially supported by the Comissionat per Universitats i Recerca de la Generalitat de Catalunya (grant No. 2021-SGR-01015). EP was also partially supported by PAIDI grants FQM-298, and ProyExcel 00780 “Operator Theory: an interdisciplinary approach” (2021), of the Junta de Andalucía. JB was also partially supported by MINECO (grant PID2024-155800NB-C32). JB and LC were partially supported by the Spanish State Research Agency through Consolidacion Investigadora program No. CNS2022-135340. EV was also partially supported
by PID2025-168310NB-I00, financed by MICIU/AEI/10.13039/501100011033 and the FSE+},
keywords = {von Neumann regular ring},
keywords = {refinement monoid},
keywords = {separated graph},
keywords = {real rank zero C*-algebra},
title = {Super adaptable graphs and the realization problem},
doi = {10.48550/arXiv.2609.21420},
author = {Ara, Pere and Bosa, Joan and Cantier, Laurent and Pardo Espino, Enrique and Vilalta, Eduard},
}