On Presentations of the Addition over the Reals
Andrey S. Morozov · Lobachevskii Journal of Mathematics · 2025
We prove that there exists $$2^{\omega}$$ non- $$\Sigma$$ -isomorphic and (even pairwise non- $$\Sigma$$ -embeddable) $$\Sigma$$ -presentations of the additive group of the real numbers in the hereditarily finite superstructure over the ordered field of the real numbers.