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On conjectures and problems of Ruzsa concerning difference graphs of S-units

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Given a finite nonempty set of primes S, we build a graph \({\mathcal{G}}\) with vertex set \({\mathbb{Q}}\) by connecting \({x, y \in \mathbb{Q}}\) if the prime divisors of both the numerator and denominator of xy are from S. In this paper we resolve two conjectures posed by Ruzsa concerning the possible sizes of induced nondegenerate cycles of \({\mathcal{G}}\), and also a problem of Ruzsa concerning the existence of subgraphs of \({\mathcal{G}}\) which are not induced subgraphs.

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Correspondence to D. Kreso.

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Ćustić, A., Hajdu, L., Kreso, D. et al. On conjectures and problems of Ruzsa concerning difference graphs of S-units. Acta Math. Hungar. 146, 391–404 (2015). https://doi.org/10.1007/s10474-015-0513-x

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  • DOI: https://doi.org/10.1007/s10474-015-0513-x

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