Alternative LISA-TAIJI networks: Detectability of the Parity Violation in Stochastic Gravitational Wave Background

Abstract

The detection of parity violation in the isotropic stochastic gravitational wave background (SGWB) will serve a crucial probe for new physics, particularly in parity-violating theories of gravity. The joint observations by the planned space-borne gravitational wave detectors, LISA and TAIJI, will offer a unique opportunity to observe such effects in the millihertz (mHz) band. This study evaluates the detectability of parity violation in the SGWB using two network configurations: LISA-TAIJIp and LISA-TAIJIm. The former configuration consists of LISA (inclined at $+60^\circ$ relative to the ecliptic plane) and TAIJIp (also inclined at $+60^\circ$), while the latter network pairs LISA with TAIJIm (inclined at $-60^\circ$). Our analysis demonstrates that the sensitivity of the LISA-TAIJIm network to parity violation in the SGWB is approximately one order of magnitude greater than that of the LISA-TAIJIp network at lower frequencies. To quantify the performance of the two networks, we evaluate the signal-to-noise ratios for different spectral shapes, including power-law, single-peak, and broken power-law models, and estimate parameter determination using the Fisher information matrix. The results confirm that LISA-TAIJIm outperforms LISA-TAIJIp in detecting the SGWB with circular polarization components, offering a superior opportunity to test parity-violating gravitational constraints on various mechanisms in the mHz band.