Hostname: page-component-586b7cd67f-gb8f7 Total loading time: 0 Render date: 2024-11-26T12:07:28.279Z Has data issue: false hasContentIssue false

Pure-projective modules and positive constructibility

Published online by Cambridge University Press:  12 March 2014

T. G. Kucera
Affiliation:
Department of Mathematics, University of Manitoba, Winnipeg, Manitoba, CanadaR3T 2N2, E-mail: [email protected]
Ph. Rothmaler
Affiliation:
Institut Für Logik, Christian-Albrechts-Universitätzu Kiel, D-24098 Kiel, Germany, E-mail: [email protected] Institut Für Logik, Christian-Albrechts-Universitätzu Kiel, D-24098 Kiel, Germany, E-mail: [email protected]

Extract

In modules many ‘positive’ versions of model-theoretic concepts turn out to be equivalent to concepts known in classical module theory—by ‘positive’ we mean that instead of allowing arbitrary first-order formulas in the model-theoretic definitions only positive primitive formulas are taken into consideration. (This feature is due to Baur's quantifier elimination for modules, cf. [Pr], however we will not make explicit use of it here.) Often this allows one to combine model-theoretic methods with algebraic ones. One instance of this is the result proved in [Rot1] (see also [Rot2]) that the Mittag-Leffler modules are exactly the positively atomic modules. This paper is parallel to the one just mentioned in that it is proved here, Theorem 3.1, that the pure-projective modules are exactly the positively constructible modules. The following parallel facts from module theory and from model theory led us to this result: every pure-projective module is Mittag-Leffler and the converse is true for countable (in fact even countably generated) modules, cf. [RG]; every constructible model is atomic and the converse is true for countable models, cf. [Pi].

Type
Research Article
Copyright
Copyright © Association for Symbolic Logic 2000

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

REFERENCES

[AF]Azumaya, G. and Facchini, A., Rings of pure global dimension zero and Mittag-Leffler modules, Journal of Pure and Applied Algebra, vol. 62 (1989), pp. 109122.CrossRefGoogle Scholar
[JL]Jensen, C. U. and Lenzing, H., Model theoretic algebra, Gordon and Breach, New York, 1989.Google Scholar
[Kap]Kaplansky, I., Projective modules, Annals of Mathematics, vol. 68 (1958), pp. 372377.CrossRefGoogle Scholar
[Pi]Pillay, A., An introduction to stability theory, Oxford Logic Guides, vol. 8, Oxford, 1983.Google Scholar
[Pr]Prest, M., Model theory and modules, London Mathematical Society Lecture Notes Series, vol. 130, Cambridge, 1988.CrossRefGoogle Scholar
[PPR]Puninski, G. E., Prest, M., and Rothmaler, Ph., Rings described by various purities, Communications in Algebra, vol. 27 (1999), pp. 21272162.CrossRefGoogle Scholar
[RG]Raynaud, M. and Gruson, L., CritÈres de platitude et de projectivitÉ, Seconde partie, Inventiones Mathematical vol. 13 (1971), pp. 5289.CrossRefGoogle Scholar
[Rot1]Rothmaler, Ph., Mittag-Leffler modules and positive atomicity, Habilitationsschrift, Kiel, 1994.Google Scholar
[Rot2]Rothmaler, Ph., Mittag-Leffler modules, Proceedings of the Florence Conference on Model Theory and Algebra, Aug 20–25,1995, Annals of Pure and Applied Logic, vol. 88, 1997, pp. 227239.Google Scholar
[Rot3]Rothmaler, Ph., Purity in model theory, Proceedings of the Conferences on Model Theory and Algebra, Essen/Dresden, 1994/95, Droste, M. und Göbel, R. (Hrsg.), Algebra, Logic and Application Series, Bd. 9, Gordon and Breach, 1997, pp. 445469.Google Scholar
[War]Warfeld, R. B., Purity and algebraic compactness for modules, Pacific Journal of Mathematics, vol. 28 (1969), pp. 699719.CrossRefGoogle Scholar
[W]Wisbauer, R., Foundations of module and ring theory, Gordon and Breach, Philadelphia, 1991.Google Scholar