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arXiv · 2608.05273

Moduli Bounds from Spin-2 Sum Rules

Francesco Bertucci·James Bonifacio·Kurt Hinterbichler
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Abstract

Mirbabayi and Villadoro have provided strong numerical evidence for a universal upper bound on the mass of the lightest scalar field in gravitational Kaluza--Klein (KK) theories. This bound states that the lightest KK graviton, with mass $m_{1}$, must couple to at least one scalar with mass $m_{\rm sc}$ such that $(m_{\rm sc} /m_{1})^2 \leq 4/3$. We give a proof of this bound using the approach of the conformal bootstrap applied to sum rules for massive spin-2 scattering amplitudes. We additionally show that each heavier KK graviton, with mass $m_n$, must couple to at least one scalar with mass $m_{\rm sc}$ such that $(m_{\rm sc} /m_{n})^2 < 36/25$.

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Francesco Bertucci, James Bonifacio, Kurt Hinterbichler. 2026-08-05. Moduli Bounds from Spin-2 Sum Rules. https://arxiv.org/abs/2608.05273

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