Michele's wiki/blog

Authors: Kent Yagi, Takahiro Tanaka

Date: 23 Jun 2009

Abstract: We calculate how strong one can put constraints on the alternative theories of gravities such as Brans-Dicke and massive graviton theories with LISA. We consider the inspiral gravitational waves from NS/IMBH binaries in Brans-Dicke theory and SMBH/BH binaries in massive graviton theories. We use the 2PN waveforms including spins. We also take both precession and small eccentricity of the orbit into account. We neglect the spin of one of the binary object so that we can apply the so-called \textit{simple precession}. We perform the Monte Carlo simulations of $10ˆ4$ binaries, whose parameters include the Brans-Dicke parameter $\omega_{\mathrm{BD}}$ and the graviton Compton length $\lambda_g$. We find that including both the spin-spin coupling $\sigma$ and the small eccentricity into the binary parameters reduces the determination accuracy by an order of magnitude for the Brans-Dicke case, whilst it has less influence on massive graviton theories. On the other hand, including precession enhances the constraint on $\omega_{\mathrm{BD}}$ only 20% but it increases the constraint on $\lambda_g$ by several factors. For $(1.4+1000)M_{\odot}$ NS/BH binaries of SNR=10, one can put $\omega_{\mathrm{BD}}>7040$, whilst for $(10ˆ7+10ˆ6)M_{\odot}$ BH/BH binaries at 3Gpc, one can put $\lambda_g>4.24\times10ˆ{21}$cm, on average. This is four orders of magnitude stronger than the one obtained from the solar system experiment. From these results, it is understood that the effects of precession and eccentricity cannot be neglected in the parameter estimation analysis.

abs pdf