Résumé
The standard cosmological model assumes the Cosmological Principle. However, recent observations hint at possible violations of isotropy on large scales, possibly through late-time anisotropic expansion. Here we investigate the potential of cross-correlations between CMB lensing convergence$κ$and galaxy cosmic shear$B$ -modes as a novel probe of such late-time anisotropies. Our signal-to-noise forecasts reveal that information from the$κ$ - $B$cross-correlation is primarily contained on large angular scales ( $\ell \lesssim 200$ ). We find that this cross-correlation for a Euclid-like galaxy survey is sensitive to anisotropy at the percent level. Making use of tomography yields a modest improvement of$\sim 20\%$in detection power. Incorporating the galaxy$E$ - $B$cross-correlations would further enhance these constraints.