Bounding alternative theories of gravity with multiband GW observations

We study the constraints on alternative theories of gravity that can be determined by multiband observations of gravitational wave signals emitted from binary black hole coalescences. We focus on three types of General Relativity modifications induced by a generalized Brans-Dicke theory and two classes of quadratic gravity, Einstein-dilaton-Gauss-Bonnet and dynamical Chern-Simons. Considering a network of space- and ground-based detectors, supplied by a population of spinning binaries black holes, we show how the multiband analysis improves the existing bounds on the theory’s parameters by several orders of magnitude, for both pre- and post-Newtonian deviations. Our results also show the fundamental role played by an interferometer in the frequency range between LISA and advanced detectors, in constraining possible deviations from General Relativity.

Figure 1

Distributions of component masses $m_1$ and $m_2$ for the black hole binaries considered in this paper.

Figure 2

Power spectral density $S_n(f)$ as a function of the frequency for the four GW detectors considered in the multiband network.

Figure 3

SNR of the BBH population described in Sec. 2 for the four detectors of the multiband network. The SNR thresholds applied to the interferometers cut approximately 95% and 10% of events in the LISA and in the LIGO/Virgo bands, respectively.

Figure 4

Distributions of the $1\sigma$ upper bounds on the parameter $B$ which controls the dipole radiation flux in BD-like theories (left panel), on the coupling constants of EdGB (center panel) and of dCS (right panel). Different colors refer to measurements obtained by distinct detectors. We only consider BBH events for which the SNR satisfies the condition $\rho \ge {\rho }_{\mathrm{th}}$ (see Sec. 4a).

Figure 5

Probability distributions of the $1\sigma$ upper bounds on the parameters of the three alternative theories of gravity considered, using multiple detectors. Filled and empty histograms refer to errors computed with and without B-DECIGO, respectively.