Parity violation through CMB observations

27-31 May 2024

This focus week will be aimed at discussing intriguing signatures of parity violation in cosmological observables, with particular emphasis on the cosmic microwave background (CMB) whose photons might exhibit cosmic birefringence (CB). CB is a tracer of parity violating extensions of standard electromagnetism. Moreover, claims of parity violation in the 4-point correlation function (4PCF) of the BOSS galaxies have been recently published and tested against CMB observations, which currently are compatible with a null detection, spurring a large debate. Given their important implications on fundamental physics, both the aforementioned parity-violating (hints of) signals focused a lot of attention in the cosmological community.  We will review recent results assessing the robustness of analyses performed so far, as well as forecasts expected for forthcoming CMB and LSS experiments. We will also discuss theoretical interpretations of these signals and brainstorm to set forth new ideas or new ways to test the recent hints of detection.

Meeting program: link


  • Alessandro Gruppuso (INAF, Bologna)
  • Carlo Baccigalupi (SISSA, Trieste)
  • Nicola Bartolo (University of Padova)
  • Nicoletta Krachmalnicoff (SISSA, Trieste)
  • Paolo Natoli (University of Ferrara)


  • Stefano Arcari (University of Ferrara)
  • Carlo Baccigalupi (SISSA, Trieste)
  • Nicola Bartolo (University of Padova)
  • Karim Benaded (CNRS IAP Paris)
  • Angelo Caravano (CNRS IAP Paris)
  • Yuji Chinone (KEK Tokyo)
  • Arie Cukierman (Caltech)
  • Patricia Diego-Palazuelos (MPA Garching)
  • Matteo Galaverni (Specola Vaticana)
  • Alessandro Greco (University of Florida)
  • Alessandro Gruppuso (INAF Bologna)
  • Giulia Gubitosi (University of Napoli Federico II)
  • Eiichiro Komatsu (MPA Garching)
  • Nicoletta Krachmalnicoff (SISSA, Trieste)
  • Margherita Lembo (University of Ferrara)
  • Tommaso Moretti (University of Napoli Federico II)
  • Toshiya Namikawa (Kavli IPMU Tokyo)
  • Paolo Natoli (University of Ferrara)
  • Ippei Obata (Kavli IPMU Tokyo)
  • Simone Paradiso (INAF OAS Bologna)
  • Alessia Ritacco (University of Rome Tor Vergata)
  • Zackary Slepian (University of Florida)

This IFPU Focus Week is also supported by the MUR PRIN2022 Project “BROWSEPOL: Beyond standaRd mOdel With coSmic microwavE background POLarization”-2022EJNZ53 financed by the European Union – Next Generation EU. We acknowledge further financial support by SISSA, ASI and INFN.