Welcome from Physics Department Director and ARC Steering Committee Room: Aula Conversi, Physics Department

Study of Carbon NanoTubes for Light Dark Matter Detection

• Alice Apponi (Istituto Nazionale di Fisica Nucleare)

Room: Aula Conversi, Physics Department The common approach for the dark matter direct detection is to look for the elastic scattering on the nuclei of the target. If light dark matter (MeV-GeV range) is considered, the recoil of electrons is instead a more valuable solution since the available energy may be enough to extract a single electron from the target. In the context of the development of a novel detector, the study of vertically-aligned carbon nanotubes as an anisotropic target for the directional light dark matter search is reported. If the energy transferred is enough to overcome the work function, the scattering with light dark matter can lead to the emission of a valence electron from carbon. This electron can eventually reach the exit of the nanotubes where an electric field drives it toward a silicon sensor. In order to study the behaviour (directionality) of low energy electrons emitted from vertically-aligned carbon nanotubes, angular dependent photoemission with UV-rays (21.2 eV and 40.8 eV) is carried on. On the other hand, the response of a silicon APD to low-energy electrons has been characterised with a custom-made monochromatic electron gun, which can provide electrons in the energy range of 90-900 eV with a 45 meV resolution.

Search for r-modes gravitational waves from PSR J0537-6910

• Alessio Zicoschi (EPFL)

Room: Aula Conversi, Physics Department La pulsar PSR J0537-6910 è ben nota alla comunità astrofisica per la sua frequente attività di glitching. Di recente, misure accurate del suo braking index nei periodi inter-glitch hanno suggerito la possibilità che alcuni modi di eccitazione del fluido stellare, detti r-modes, siano attivati in questa pulsar. Secondo le stime teoriche, la dissipazione di energia di queste eccitazioni può generare onde gravitazionali continue potenzialmente misurabili dai rivelatori di onde gravitazionali odierni. Nel mio progetto di tesi di laurea magistrale, ho sviluppato una metodologia innovativa per la ricerca di onde gravitazionali continue associate all’emissione da r-modes dalla suddetta pulsar. Infine, ho applicato questa metodologia ai dati provenienti dal run O3 degli interoferometri LIGO-Virgo.

Into the wilds of strong gravity

• Alexandru Dima (Illinois U., Urbana)

Room: Aula Conversi, Physics Department In the current age of Gravitational Physics, despite being put to the strictest observational tests, General Relativity still holds fast as the most successful theory of gravity. Even its most striking predictions -i.e. black holes and gravitational waves- found further confirmation in the recent results by the Event Horizon Telescope and LIGO-Virgo-KAGRA collaborations. As gravitational experiments are expected to steadily grow in number and accuracy over the next decade, it is worth asking whether we could still expect gravity to hide some surprises for us. In this talk, I will discuss my research journey into strong gravity-in General Relativity and beyond- and present examples of how gravity might still surprise us.

Probing new physics on the horizon of black holes with gravitational waves

• Elisa Maggio (AEI, Potsdam)

Room: Aula Conversi, Physics Department Black holes are the most compact objects in the Universe. According to general relativity, black holes have a horizon that hides a singularity where Einstein’s theory breaks down. Recently, gravitational waves opened the possibility to probe the existence of horizons and investigate the nature of compact objects. This is of particular interest given some quantum-gravity models which predict the presence of horizonless and singularity-free compact objects. Such exotic compact objects can emit a different gravitational-wave signal relative to the black hole case. In this talk, we analyze the stability of horizonless compact objects, and derive a generic framework to compute their characteristic oscillation frequencies. We provide an analytical, physically-motivated template to search for the gravitational-wave echoes emitted by these objects in the late-time postmerger signal. Finally, we infer how extreme mass-ratio inspirals observable by future gravitational-wave detectors will allow for model-independent tests of the black hole paradigm.