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by 30ss 6036 days ago
Your reasoning is correct, so it means that integers are not definable inside "real arithmetic".

http://en.wikipedia.org/wiki/Real-closed_field

If you don't believe this, try writing down a formula in the language of this theory that says "x is an integer".

Ultimately, the issue is that the first-order theory of real closed fields contains no axiom approaching the induction scheme of PA in power.