IAS Program on Particle Theory - Cosmic Birefringence vs the Need of a New Light Field Beyond the Standard Model Particle Content

Abstract

The recent analysis of the cosmic microwave background (CMB) indicates a rotation of the polarization plane of the CMB photons from the last scattering surface, called cosmic birefringence. A standard explanation for this effect is a parity-odd scalar field coupled to photons, whose coherent motion, if exists, breaks parity in the photon sector along the propagation for a cosmological distance. To examine the degree of validity of this consideration, we explore whether the non-zero cosmic birefringence can be interpreted within the framework of the Standard Model effective field theory (SMEFT). Our systematic study reveals that indeed none of the operators in SMEFT would be able to give the reported birefringence angle. Should this observational result be confirmed, therefore, the existence of a new particle beyond SMEFT that is much lighter than the electroweak scale would be an inevitable conclusion.


About the Speaker

Dr. Ryo NAMBA is currently a senior research scientist of the Interdisciplinary Theoretical and Mathematical Sciences Program (iTHEMS) at RIKEN, working on a wide spectrum of the field of theoretical cosmology. He obtained his PhD from the University of Minnesota, after which he engaged in postdoctoral research positions at Kavli IPMU, McGill University and Tsung-Dao Lee Institute at Shanghai Jiao Tong University, before joining RIKEN iTHEMS.


About the Program

For more information, please refer to the program website at http://iasprogram.ust.hk/particle_theory.


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