Solution

ID: past-exam-of-the-model-theory-course-of-the-university-of-oxford/2011/1/b/i/gamma/solution

No. Definability of a function means definability of its graph. The same additive structure automorphism would have to preserve the graph of multiplication. It sends the graph point to , which is not a multiplication-graph point because . This contradicts automorphism invariance of parameter-free definability.

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