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  • Open Access

Observing dark matter decays to gravitons via graviton-photon conversion

David I. Dunsky1,*, Gordan Krnjaic2,3,4,†, and Elena Pinetti5,2,4,6,‡

  • 1Center for Cosmology and Particle Physics, Department of Physics, New York University, New York, New York, USA
  • 2Theoretical Physics Division, Fermi National Accelerator Laboratory, Batavia, Illinois, USA
  • 3Department of Astronomy & Astrophysics, University of Chicago, Chicago, Illinois USA
  • 4Kavli Institute for Cosmological Physics, University of Chicago, Chicago, Illinois USA
  • 5Center for Computational Astrophysics, Flatiron Institute, New York, New York 10010, USA
  • 6Emmy Noether Fellow, Perimeter Institute for Theoretical Physics, 31 Caroline Street N., Waterloo, Ontario, N2L 2Y5, Canada

  • *Contact author: ddunsky@nyu.edu
  • †Contact author: krnjaicg@fnal.gov
  • ‡Contact author: epinetti@flatironinstitute.org
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Phys. Rev. D 114, 015045 – Published 29 July, 2026

DOI: https://doi.org/10.1103/yvs5-67cj

Abstract

Since dark matter is only known to have gravitational interactions, it may plausibly decay to gravitons on cosmological timescales. Although such a scenario can be easily realized, there are currently no known limits on this possibility based on indirect-detection methods. We propose a new search strategy that exploits the Gertsenshtein effect, whereby the gravitons produced in dark matter decays can convert to photons in large-scale magnetic fields along the line of sight to an observer. These conversions primarily occur within cosmological filaments which occupy a large (order unity) volume fraction and contain ∼10–100  nG fields with ∼Mpc coherence lengths. Thus, dark matter decays to gravitons predict an irreducible population of extragalactic photons, which we constrain using the extragalactic gamma-ray background measured by the Fermi-LAT telescope. Using this method, we derive the first-ever constraints on the dark matter lifetime in the 0.1  GeV−108  GeV mass range, contingent on the assumed filament magnetic field strength. We also make projections for the Advanced Particle-astrophysics Telescope, which can improve sensitivity to this dark matter decay channel by an order of magnitude beyond those we set using Fermi-LAT data.

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Outline

Information

Phys. Rev. D 114, 015045– Published 29 July, 2026
  • Received 11 May 2025
  • Revised 13 November 2025
  • Accepted 23 June 2026
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