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An ω1-categorical ring which is not almost strongly minimal

Published online by Cambridge University Press:  12 March 2014

K.-P. Podewski
Affiliation:
Technische Universität Hannover, Hannover, West Germany (BRD)
J. Reineke
Affiliation:
Technische Universität Hannover, Hannover, West Germany (BRD)

Extract

A very important example of almost strongly minimal theories are the algebraically closed fields. A. Macintyre has shown [3] that every ω1-categorical field is algebraically closed. Therefore every ω1-categorical field is almost strongly minimal. It will be shown that not every ω1-categorical ring is almost strongly minimal.

Let R0 be the factor ring C[y/(y2), where C[y] is the ring of polynomials in the indeterminate y over the field of complex numbers and (y2) the ideal generated by y2 in C[y].

It is straightforward to prove that R0 has the following properties:

1. R0 is a commutative ring with identity.

2. R0 is of characteristic 0.

3. For every polynomial p(x) = ∑ a1x1R0[x] with of ai2 ≠ 0 for some i > 0 there is an aR0 such that p(a) · p(a) = 0.

4. For all x, yR0 such that x2 = 0 and y ≠ 0 there exists a zR0 with y · z = x.

5. There is an x ≠ 0 such that x2 = 0.

These properties can be ∀∃-axiomatised in a countable first order logic (see [4]). Let T be the set of these sentences. With Theorem 7 we get that T is model-complete.

If R is a model of T then I shall denote {aRa2 = 0}.

Type
Research Article
Copyright
Copyright © Association for Symbolic Logic 1974

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References

REFERENCES

[1] Baldwin, J. T. and Lachlan, A. H., On strongly minimal sets, this Journal, vol. 36 (1971), pp. 79–96.Google Scholar
[2] Baldwin, J. T., Almost strongly minimal theories. I, this Journal, vol. 37 (1972), pp. 487–493.Google Scholar
[3] Macintyre, A., On ω1-categorical theories of fields, Fundamenta Mathematicae, vol. 71 (1971), pp. 1–25.CrossRefGoogle Scholar
[4] Sacks, G. E., Saturated model theory, Mathematics Lecture Note Series, Benjamin, Reading, Mass., 1972.Google Scholar
[5] Zariski, O. and Samuel, P., Commutative algebra. II, Van Nostrand, Princeton, N.J., 1960.Google Scholar