Taiji Resolving Power for the Transverse Scalar Mode of Gravitational Waves

Abstract

We investigate how small a co-propagating transverse-scalar component can be resolved by Taiji in an already identified bright tensor chirp. Using a source-tracked tensor-null response, we formulate the problem in terms of the minimum resolvable scalar strain fraction and evaluate it over the sky. For a one-year benchmark chirp with tensor signal-to-noise ratio ${\rho }_T=1000$, we find that Taiji can rule out transverse-scalar strain fractions ${\epsilon }_b\gtrsim 0.532\%$ at the all-sky median level. The threshold scales as ${\epsilon }_{b,\min }\propto {\rho }_T^{-1}$, so brighter tensor events can probe correspondingly smaller scalar fractions. We further find that this sub-percent resolving power remains predictable under small source-parameter mismatches through the associated tensor-leakage structure.

23 pages, 7 figures, 4 tables