Probing Cosmic Inflation from the South Pole with BICEP Array

Cosmic inflation proposes that the universe underwent an epoch of exponential expansion within the first fraction of a second after the Big Bang. This paradigm addresses several fundamental challenges in cosmology, including the horizon, flatness, and monopole problems, while providing a mechanism for the origin of primordial density fluctuations. A definitive test of inflation lies in the detection of primordial gravitational waves through their imprint on the cosmic microwave background (CMB) as large-scale B-mode polarization. A robust measurement of this signal would provide compelling evidence for inflation and place powerful constraints on the landscape of viable inflationary models.

The BICEP/Keck program is designed to search for this signature using highly sensitive, small-aperture telescopes located at the South Pole. The newest stage of this effort, the BICEP Array, comprises four receivers optimized for degree-scale polarization measurements. To date, three of the four receivers have been deployed. During the 2024–25 austral summer season, the most recent telescope was installed with a partially completed focal plane containing three 220 GHz detector modules, each with 648 detectors. Additional 220 GHz and 270 GHz modules were deployed during the most recent season to enhance foreground characterization and overall sensitivity.

In this talk, I will review the theoretical motivation for inflation, summarize the current deployment status of the BICEP Array, and present sensitivity forecasts for the constraints we aim to achieve on primordial B-mode polarization.

Dr. Sofia Fatigoni, California Institute of Technology (USA)

Sofia Fatigoni is a research scientist at Caltech specializing in experimental cosmology. She earned her Ph.D. from the University of British Columbia, where she worked on the BICEP Array telescope and the search for primordial B-mode polarization in the cosmic microwave background. As a member of the BICEP Array hardware team, she has participated in five Antarctic deployments and helped install three receivers at the South Pole. Her research focuses on testing cosmic inflation and advancing instrumentation for next-generation CMB experiments. As part of her master’s degree, she has also worked on radio observations of the Andromeda Galaxy with the Sardinia Radio Telescope, producing one of the most detailed 6.6 GHz maps of M31 and contributing to the study of anomalous microwave emission.