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arXiv · 2603.04330

Single-minus graviton tree amplitudes are nonzero

Alfredo Guevara·Alexandru Lupsasca·David Skinner·Andrew Strominger·Kevin Weil
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Abstract

Single-minus tree-level $n$-graviton scattering amplitudes are revisited. Often presumed to vanish, they are shown here to be nonvanishing for certain "half-collinear" configurations existing in Klein space or for complexified momenta. A Berends-Giele recursion relation for these amplitudes is derived and solved in a form involving a sum over trees. In a restricted kinematic decay region, this solution simplifies significantly to an $(n{-}2)$-fold product of soft factors. It is further shown in this region that, combined with suitable analyticity assumptions, the $n$-graviton amplitude is generated by a recursive $\mathcal{L}w_{1+\infty}$ Ward identity with the three-graviton amplitude as a seed.

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Alfredo Guevara, Alexandru Lupsasca, David Skinner, Andrew Strominger, Kevin Weil. 2026-03-04. Single-minus graviton tree amplitudes are nonzero. https://arxiv.org/abs/2603.04330

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