The price to pay for enhanced physico-chemical insight: Nonlinear ultrafast spectroscopy

• Pietro Lussana

In this talk, we introduce the fundamental concept at the core of spectroscopy: the radiation-matter interaction. We then introduce the concept of polarization: starting from its basic formulation and moving toward refined versions that include nonlinearity and ultrafast effects. This is a crucial step for understanding how to gain more detailed information about our samples. The power of these techniques comes at a cost. The three major challenges are: the coexistence of multiple background phenomena, high noise levels, and a strong sensitivity to instrumental parameters and imperfections. Our job is to mitigate as much as possible these issues.

Dicussion

Testing gravity with compact objects

• Lodovico Capuano

Gravitational waves have opened an unprecedented window onto the strong-field, dynamical regime of gravity, allowing us to probe the nature of compact objects and test General Relativity in extreme conditions. In this talk, I will explore how deviations from standard predictions may arise in binary coalescences, focusing on two key phases: the inspiral and the ringdown. During the inspiral, the presence of additional scalar charges can modify the dynamics and imprint characteristic signatures in the waveform, offering a sensitive probe of beyond-GR scenarios. Moving to the post-merger phase, I will discuss advances in ringdown modelling, including nonlinear effects and potential departures from the classical quasi-normal mode picture.

Discussion