Korean J. Math. Vol. 34 No. 2 (2026) pp.147-164
DOI: https://doi.org/10.11568/kjm.2026.34.2.147

Continuous Comodules

Main Article Content

Nikken Puspita
Indah Wijayanti
Budi Surodjo

Abstract

Let $R$ be a commutative ring with unity and $C$ an $R$-coalgebra. The ring $R$ is clean if every elements $r$ in $R$ is the sum of a unit and an idempotent element of $R$. An $R$-module $M$ is clean if the endomorphism ring of $M$ over $R$ is clean. Moreover, every continuous module is clean. We adapt this idea to comodules and coalgebras. A $C$-comodule $M$ is called a clean comodule if the $C$-comodule endomorphisms of $M$ are clean. We introduce continuous comodules and proved that every continuous comodules is a clean comodules.



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References

[1] W. K. Nicholson, Lifting idempotents and exchange rings, Trans. Amer. Math. Soc. 229 (1977), 269–278. Google Scholar

[2] R. B. Warfield Jr., Exchange rings and decompositions of modules, Math. Ann. 199 (1972), 31–36. Google Scholar

[3] P. Crawley and B. J´onsson, Refinements for infinite direct decompositions of algebraic systems, Pacific J. Math. 14 (1964), 797–855. https://doi.org/10.2140/pjm.1964.14.797 Google Scholar

[4] W. K. Nicholson and K. Varadarajan, Countable linear transformations are clean, Proc. Amer. Math. Soc. 126 (1998), 61–64. Google Scholar

[5] M. ´O. Searcoid, Perturbation of linear operators by idempotents, Irish Math. Soc. Bull. 39 (1997), 10–13. Google Scholar

[6] W. K. Nicholson, K. Varadarajan, and Y. Zhou, Clean endomorphism rings, Arch. Math. 83 (2004), 340–343. Google Scholar

[7] V. P. Camillo, D. Khurana, T. Y. Lam, W. K. Nicholson, and Y. Zhou, Continuous modules are clean, J. Algebra 304 (2006), 94–111. Google Scholar

[8] V. P. Camillo, D. Khurana, T. Y. Lam, W. K. Nicholson, and Y. Zhou, A short proof that continuous modules are clean, In: Contemporary Ring Theory 2011, World Sci. Publ., Singapore (2012), 165–169. Google Scholar

[9] T. Brzezi´nski and R. Wisbauer, Corings and Comodules, Cambridge Univ. Press, Cambridge (2003). https://doi.org/10.1017/CBO9780511546495 Google Scholar

[10] S. H. Mohamed and B. J. Muller, Continuous and Discrete Modules, London Math. Soc. Lecture Note Ser. 147, Cambridge Univ. Press, Cambridge (1990). Google Scholar

[11] N. P. Puspita, I. E. Wijayanti, and B. Surodjo, Clean coalgebras and clean comodules from finitely generated projective modules, Algebra Discrete Math. 31 (2021), 251–260. Google Scholar

[12] N. P. Puspita, I. E. Wijayanti, and B. Surodjo, The necessary and sufficient condition of clean R-coalgebra e ⇀ C ↼ e, J. Indones. Math. Soc. 28 (2022), 215–220. Google Scholar

[13] N. P. Puspita and I. E. Wijayanti, Bi-clean and clean Hopf modules, AIMS Math. 7 (2022), 18784–18792. Google Scholar

[14] R. Wisbauer, Foundations of Module and Ring Theory, Gordon and Breach, Philadelphia (1991). Google Scholar

[15] A. Tuganbayev, Rings Close to Regular, Kluwer Acad. Publ., Dordrecht (2002). Google Scholar