Astroparticle Physics seminars

Cosmological surveys can reveal new particles through signals hidden among astrophysical foregrounds. This talk examines axion conversion of microwave photons in magnetized galactic halos, using Planck, unWISE and ACT observations with improved component separation. It then turns to inflationary particle signatures in galaxy clustering, including a constraint on the primordial four-point amplitude from DESI galaxies and quasars. The discussion highlights both the reach of these measurements and the systematic challenges of analysing extremely large scales.

A weak attractive interaction confined to dark matter can outweigh gravity over subgalactic distances. This talk studies its effects on collapse and stable bound structures when the force is screened beyond roughly kiloparsec scales. Delaying its onset until low cosmic density avoids early-Universe and galaxy-structure constraints. For fermionic matter, the additional attraction can support much lighter particles against degeneracy pressure; a density-triggered phase transition provides a concrete delayed-activation mechanism.

Claudio Manzari connects astrophysical observations and precision flavor measurements to two unresolved aspects of CP symmetry. For the strong CP problem, the talk considers QCD axions produced in a supernova core and converted to gamma rays by surrounding magnetic fields. A Galactic supernova could expose this distinctive transient, motivating the GALAXY network of telescopes monitoring the full sky. The second part examines the origin of flavor-sector CP violation through precise measurements of the CKM unitarity triangle. Possible hints of spontaneous CP violation are discussed alongside their implications for quark flavor and the fundamental symmetries of matter.

Elena Pinetti explores astrophysical searches for dark matter across a wide range of masses and interactions. Observations complement laboratory searches for particles such as axions and weakly interacting massive particles. The talk develops strategies that turn observatories into probes of fundamental physics, including infrared observations with JWST for axions and radio studies of cosmic filaments for WIMP scenarios.

The Princeton Axion Search targets dark-matter axions between the mass ranges addressed by cavity haloscopes and DMRadio. This talk describes cryogenics, magnets, resonators and near-quantum-limited amplifiers for the 200–500 MHz range. It also reviews collaborations on superconducting resonators, conduction-cooled solenoids and readout strategies that aim to exceed the standard quantum limit.

Tien-Tien Yu examines observational signatures of ultralight scalar dark matter with quadratic couplings to Standard Model fields. The couplings change fundamental constants over time, affecting primordial light-element production, the microwave-background power spectrum and tests of the equivalence principle. The talk follows these effects from the early Universe to present experiments and explains how current cosmological measurements constrain this class of scalar-dark-matter models.