Universally defining $\mathbb{Z}$ in $\mathbb{Q}$ with $10$ quantifiers

In: Journal of the London Mathematical Society 109.2 (2024), e12864 We show that for a global field $K$, every ring of $S$-integers has a universal first-order definition in $K$ with $10$ quantifiers. We also give a proof that every finite intersection of valuation rings of $K$ has an existential first-order definition in $K$ with $3$ quantifiers.