Anomalies in the cosmic microwave background

Abstract:
The LambdaCDM model, with its six fundamental parameters, provides a remarkably successful framework for understanding the early Universe. 

However, the pursuit of new physics beyond this standard model remains an active area of research, and there are several observations in tension with this model. One intriguing aspect of the cosmic microwave background (CMB) radiation is the large-scale dipole, which spans the entire sky. While this dipole is predominantly attributed to the Doppler effect from our motion through space, there remains the possibility of a contribution from a large non-adiabatic mode in the early Universe. If true, this would fundamentally change our understanding of the Universe.

In this work, I investigate the origins of the CMB dipole and present a novel measurement of a specific term correlated with the thermal Sunyaev-Zeldovich (tSZ) effect, marking the first such analysis. I provide a historical overview of dipole signal detections and identify several promising avenues for future exploration. Additionally, I explore another anomalous signal, known as cosmic birefringence, which could imply parity violation in the Universe -- potentially driven by exotic axion-like dark matter or forms of dark energy. While previous detections primarily relied on harmonic analysis, I adopt a map-space approach, allowing for the examination of spatial variations and the detection of any anisotropic components across the sky.

Finally, I present predictions for upcoming cosmic birefringence measurements by next-generation experiments such as LiteBIRD, highlighting the potential for significant discoveries in the near future.