Ginevra Braga (GSSI)

Path integrals for Gravitational Waves: New ways to describe wave effects

An intriguing aspect of gravitational wave lensing is the emergence wave-effects: interference and diffraction patterns in the waveforms due to finite size effects, occurring when the wave’s wavelength is comparable to the Schwarzschild radius of the lens. These phenomena are particularly interesting because they induce frequency dependent modifications in the waveforms, allowing for a better lens’ parameter estimation, especially if the lensing event has an electromagnetic counterpart in the opposite optical regime. Despite the promising potential of wave-optics effects, our current theoretical tools, based on the diffraction integral, rely on two main assumptions that limit their effectiveness: the eikonal and paraxial approximations on one hand, and the neglect of spin effects on the other. In this talk I will present new approaches to this phenomenon. The first one based on the established worldline technique in field theory, illustrating its robustness as the generalization of the diffraction integral, going beyond all of the limitations mentioned. The second one based on techniques of open quantum systems, which can be crucial in describing systems of many lenses.