GW170817 wave speed

GW vs EM speed from binary neutron-star merger — DCT predicts exact equality.

Prediction	\(c_{GW}/c = 1\) exactly (massless graviton, no Lorentz violation)
Measured	\(\|c_{GW}/c - 1\| < 10^{-15}\) (LVC + Fermi GBM 2017)
Residual	0.00σ
Status	PASS
Source paper	DCT-SBD-01

Mechanism

DCT propagates gravitational waves on the Einstein-frame light cone (no disformal kinetic mixing). \(c_{GW} = c\) to all orders in the BD action. The GW170817 multimessenger constraint \(|c_{GW}/c - 1| < 10^{-15}\) is consistent at \(0\sigma\).

Derivation

The gravitational-wave dispersion relation in DCT is \(\omega^2 = c^2 k^2\) (DCT-SBD-01); the tie-field background does not couple to the transverse-traceless graviton sector at leading order. No Lorentz-violating term is generated by the canonical action.

Python verification

The verification script for this observable is ligo_gravitational_wave_analysis.py. Run it with python3 ligo_gravitational_wave_analysis.py to reproduce the canonical DCT result against the public-archive measurement source listed above.

References

GW170817 PRL 119, 161101
Source paper: DCT-SBD-01

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