Sh:880

• Göbel, R., & Shelah, S. (2007). Absolutely indecomposable modules. Proc. Amer. Math. Soc., 135(6), 1641–1649. arXiv: 0711.3011 DOI: 10.1090/S0002-9939-07-08725-4 MR: 2286071
• Abstract:
  A module is called absolutely indecomposable if it is directly indecomposable in every generic extension of the universe. We want to show the existence of large abelian groups that are absolutely indecomposable. This will follow from a more general result about R-modules over a large class of commutative rings R with endomorphism ring R which remains the same when passing to a generic extension of the universe. It turns out that ‘large’ in this context has the precise meaning, namely being smaller then the first \omega-Erdos cardinal defined below. We will first apply result on large rigid trees with a similar property established by Shelah in 1982, and will prove the existence of related ‘R_\omega-modules’ (R-modules with countably many distinguished submodules) and finally pass to R-modules. The passage through R_\omega-modules has the great advantage that the proofs become very transparent essentially using a few ‘linear algebra’ arguments accessible also for graduate students. The result gives a new construction of indecomposable modules in general using a counting argument.
• Version 2006-05-06_11 (10p) published version (9p)

@article{Sh:880,
 author = {G{\"o}bel, R{\"u}diger and Shelah, Saharon},
 title = {{Absolutely indecomposable modules}},
 journal = {Proc. Amer. Math. Soc.},
 fjournal = {Proceedings of the American Mathematical Society},
 volume = {135},
 number = {6},
 year = {2007},
 pages = {1641--1649},
 issn = {0002-9939},
 mrnumber = {2286071},
 mrclass = {13L05 (03E55 13C05 20K20 20K30)},
 doi = {10.1090/S0002-9939-07-08725-4},
 note = {\href{https://arxiv.org/abs/0711.3011}{arXiv: 0711.3011}},
 arxiv_number = {0711.3011}
}