Kavli Affiliate: Misao Sasaki
| First 5 Authors: Yusuke Mikura, Yusuke Mikura, , ,
| Summary:
Gravitational waves (GWs) distort galaxy shapes through the tidal effect,
offering a novel avenue to probe the nature of gravity. In this paper, we
investigate how extra GW polarizations beyond those predicted by general
relativity imprint observable signatures on galaxy shapes. Since galaxy shapes
are measured as two-dimensional images projected onto the celestial sphere, we
present three-dimensional statistical quantities of the projected tidal tensor
sourced by the tensor perturbation. We show that the presence of extra
polarization modes modifies both the amplitude and angular dependence of the
correlation functions. Furthermore, we identify a distinct observational
channel for probing parity violation in helicity-two and helicity-one modes. In
particular, we show that if they propagate at different speeds, galaxy surveys
can disentangle the source of parity violation. Our findings establish a
theoretical framework for using upcoming large-scale galaxy surveys to test
modified gravity theories through the polarization content of GWs.
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