{"paper":{"title":"On-Shell Amplitudes and Black-Hole Perturbations: Exact Reissner-Nordstr\\\"om Mixing","license":"http://creativecommons.org/licenses/by/4.0/","headline":"","cross_cats":["gr-qc","hep-ph"],"primary_cat":"hep-th","authors_text":"Kento Takahara, Teppei Kitahara","submitted_at":"2026-08-12T06:27:46Z","abstract_excerpt":"Can flat-space on-shell amplitudes determine the channel basis of a coupled black-hole perturbation problem? We address this question for electromagnetic and gravitational perturbations of a Reissner-Nordstr\\\"{o}m (RN) black-hole. We organize the minimally coupled photon-graviton tree amplitudes off a heavy charged source into a $2\\times 2$ channel-space matrix and perform a parity-resolved Jacob-Wick partial-wave projection. For every radiative multipole $\\ell \\geq 2$ and in both parity sectors, we show that the trace-free fixed-source partial-wave matrix is exactly proportional to the trace-"},"claims":{"count":0,"items":[],"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"source":{"id":"2608.11703","kind":"arxiv","version":1},"verdict":{"id":null,"model_set":{},"created_at":null,"strongest_claim":"","one_line_summary":"","pipeline_version":null,"weakest_assumption":"","pith_extraction_headline":""},"integrity":{"clean":true,"summary":{"advisory":0,"critical":0,"by_detector":{},"informational":0},"endpoint":"/pith/2608.11703/integrity.json","findings":[],"available":true,"detectors_run":[],"snapshot_sha256":"c28c3603d3b5d939e8dc4c7e95fa8dfce3d595e45f758748cecf8e644a296938"},"references":{"count":0,"sample":[],"resolved_work":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57","internal_anchors":0},"formal_canon":{"evidence_count":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"author_claims":{"count":0,"strong_count":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"builder_version":"pith-number-builder-2026-05-17-v1"}