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Partitions of products

Published online by Cambridge University Press:  12 March 2014

Carlos A. Di Prisco
Affiliation:
Departamento de Matemáticas, Instituto Venezolano de Investigaciones Cientificas, Apartado 21827, Caracas 1020A, Venezuela, E-mail: cdiprisc@conicit.ve
James M. Henle
Affiliation:
Smith College, Northampton, Massachusetts 01063, E-mail: jhenle@smith.edu

Extract

We will consider some partition properties of the following type: given a function F: ωω →2, is there a sequence H0, H1, … of subsets of ω such that F is constant on ΠiεωHi? The answer is obviously positive if we allow all the Hi's to have exactly one element, but the problem is nontrivial if we require the Hi's to have at least two elements. The axiom of choice contradicts the statement “for all F: ωω→ 2 there is a sequence H0, H1, H2,… of subsets of ω such that {i|(Hi) ≥ 2} is infinite and F is constant on ΠHi”, but the infinite exponent partition relation ω(ω)ω implies it; so, this statement is relatively consistent with an inaccessible cardinal. (See [1] where these partition properties were considered.)

We will also consider partitions into any finite number of pieces, and we will prove some facts about partitions into ω-many pieces.

Given a partition F: ωωk, we say that H0, H1…, a sequence of subsets of ω, is homogeneous for F if F is constant on ΠHi. We say the sequence H0, H1,… is nonoverlapping if, for all i ∈ ω, ∪Hi > ∩Hi+1.

The sequence 〈Hi: i ∈ ω〉 is of type 〈α0, α1,…〉 if, for every i ∈ ω, ∣Hi∣ = αi.

We will adopt the usual notation for polarized partition relations due to Erdös, Hajnal, and Rado.

means that for every partition F: κ1 × κ2 × … × κn→δ there is a sequence H0, H1,…, Hn such that Hi ⊂ κi and ∣Hi∣ = αi for every i, 1 ≤ in, and F is constant on H1 × H2 × … × Hn.

Type
Research Article
Copyright
Copyright © Association for Symbolic Logic 1993

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References

REFERENCES

[1]Carnielli, W. and di Prisco, C. A., Some results on Polarized partition relations of higher dimension, Mathematical Logic Quarterly, vol. 39 (1993).CrossRefGoogle Scholar
[2]Erdös, P. and Rado, R., A partition calculus in set theory, Bulletin of the American Mathematical Society, vol. 62 (1956), pp. 427489.CrossRefGoogle Scholar
[3]ErdÖs, P., Hajnal, A., and Rado, R., Partition relations for cardinal numbers, Acta Mathematica Hungarica Akad. Kiadé, vol. 16 (1965), pp. 93196.CrossRefGoogle Scholar
[4]Moran, G. and Strauss, D., Countable partitions of product spaces, Mathematika vol. 27 (1980), pp. 213224.CrossRefGoogle Scholar