Weak lensing generated by vector perturbations and detectability of cosmic strings

We study the observational signature of vector metric perturbations through the effect of weak gravitational lensing. In the presence of vector perturbations, the non-vanishing signals for B-mode cosmic shear and curl-mode deflection angle, which have never appeared in the case of scalar metric perturbations, naturally arise. Solving the geodesic and geodesic deviation equations, we drive the full-sky formulas for angular power spectra of weak lensing signals, and give the explicit expressions for E-/B-mode cosmic shear and gradient-/curl-mode deflection angle. As a possible source for seeding vector perturbations, we then consider a cosmic string network, and discuss its detectability from upcoming weak lensing and CMB measurements. Based on the formulas and a simple model for cosmic string network, we calculate the angular power spectra and expected signal-to-noise ratios for the B-mode cosmic shear and curl-mode deflection angle. We find that the weak lensing signals are enhanced for a smaller intercommuting probability of the string network, $P$, and they are potentially detectable from the upcoming cosmic shear and CMB lensing observations. For $P\sim 10^{-1}$, the minimum detectable tension of the cosmic string will be down to $G\mu\sim 5\times 10^{-8}$. With a theoretically inferred smallest value $P\sim 10^{-3}$, we could even detect the string with $G\mu\sim 5\times 10^{-10}$.Comment: 39 pages, 5 figures, v2: references added, minor corrections, v3: matches version published in JCA

Evidence for the Cross-correlation between Cosmic Microwave Background Polarization Lensing from Polarbear and Cosmic Shear from Subaru Hyper Suprime-Cam

We present the first measurement of cross-correlation between the lensing potential, reconstructed from cosmic microwave background (CMB) polarization data, and the cosmic shear field from galaxy shapes. This measurement is made using data from the Polarbear CMB experiment and the Subaru Hyper Suprime-Cam (HSC) survey. By analyzing an 11 deg2 overlapping region, we reject the null hypothesis at 3.5\u3c3 and constrain the amplitude of the cross-spectrum to , where is the amplitude normalized with respect to the Planck 2018 prediction, based on the flat \u39b cold dark matter cosmology. The first measurement of this cross-spectrum without relying on CMB temperature measurements is possible owing to the deep Polarbear map with a noise level of 3c6 \u3bcK arcmin, as well as the deep HSC data with a high galaxy number density of . We present a detailed study of the systematics budget to show that residual systematics in our results are negligibly small, which demonstrates the future potential of this cross-correlation technique