## Abstract

The observation of GW170817 in both gravitational and electromagnetic waves provides a number of unique tests of general relativity. One question we can answer with this event is: do large-wavelength gravitational waves and short-frequency photons experience the same number of spacetime dimensions? In models that include additional non-compact spacetime dimensions, as the gravitational waves propagate, they "leak" into the extra dimensions, leading to a reduction in the amplitude of the observed gravitational waves, and a commensurate systematic error in the inferred distance to the gravitational wave source. Electromagnetic waves would remain unaffected. We compare the inferred distance to GW170817 from the observation of gravitational waves, d_{L} ^{GW}, with the inferred distance to the electromagnetic counterpart NGC 4993, d_{L} ^{EM}. We constrain d_{L} ^{GW} = (d_{L} ^{EM}/Mpc)^{γ} with γ = 1.01^{+0.04} _{-0.05} (for the SHoES value of H_{0}) or γ = 0.99^{+0.03} _{-0.05} (for the Planck value of H_{0}), where all values are MAP and minimal 68% credible intervals. These constraints imply that gravitational waves propagate in D=3+1 spacetime dimensions, as expected in general relativity. In particular, we find that D = 4.02^{+0.07} _{-0.10} (SHoES) and D = 3.98^{+0.07} _{-0.09} (Planck). Furthermore, we place limits on the screening scale for theories with D>4 spacetime dimensions, finding that the screening scale must be greater than ∼ 20 Mpc. We also place a lower limit on the lifetime of the graviton of t > 4.50 × 10^{8} yr.

Original language | English (US) |
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Article number | 048 |

Journal | Journal of Cosmology and Astroparticle Physics |

Volume | 2018 |

Issue number | 7 |

DOIs | |

State | Published - Jul 23 2018 |

## All Science Journal Classification (ASJC) codes

- Astronomy and Astrophysics

## Keywords

- Cosmology with extra dimensions
- gravitational waves
- modified gravity
- theory