Solution

ID: past-exam-of-the-model-theory-and-godel-s-incompleteness-theorems-course-of-the-university-of-oxford/2010/b/5/c/iii/solution

No. The parameter-free partial type
is finitely satisfiable in the ordered real field: choose a number larger than the finitely many bounds. By compactness theorem it extends to a complete type over the empty set. But no real number realizes it, by the Archimedean property. Therefore the ordered real field is not an omega-saturated model.
The named unit and addition make every integer bound expressible, even without extra parameters. This is why the obstruction is present in the ordered-field language and absent in the two reducts above.

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