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报告题目： The frequency response of gravitational wave interferometers
特邀专家： 龚云贵, 华中科技大学
报告时间：9：30 ～10:30am，Friday, Nov. 8th, 2019
Gravitational waves are perturbations of the metric of space-time. Six polarizations are possible, although general relativity predicts that only two such polarizations, tensor plus and tensor cross are present for gravitational waves. The detection of extra polarization states is the smoking gun for the modification of general relativity in strong and nonlinear regime. In this talk, we discuss the antenna response to all the six polarizations and derive the analytical formulas which are valid for any equal-arm interferometric gravitational-wave detectors without optical cavities in the arms. We find that the response function averaged over the source direction and polarization angle decreases at high frequencies which deteriorates the signal-to-noise ratio registered in the detector. Space-based gravitational wave detectors cannot keep rigid structures and precise arm length equality, so the precise equality of detector arms which is required in a ground-based interferometer to cancel the overwhelming laser noise is impossible. The time-delay interferometry method is applied to unequal arm lengths to cancel the laser frequency noise. We give analytical formulas of the averaged response functions for tensor, vector, breathing and longitudinal polarizations in different TDI combinations, and obtain their asymptotic behaviors. We also use LISA and TianQin as examples to show sensitivity curves for all six possible polarizations.