Dr Doudou Cao

PhD thesis

Causality and Unitarity in the early universe

My PhD focused on the role of fundamental principles in the study of the early universe. The two main fundamental principles I considered were causality, the idea that information can only travel as fast as light, and unitarity, the idea that information is preserved under time evolution. The observable under scrutiny was the statistics of the temperature fluctuations of the cosmic microwave background. While this background is very close to being homogeneous and isotropic, it presents slight anisotropies. The distribution of these anisotropies encodes information on what happened in the early universe. My research suggested that the mathematical structure of these statistics is simpler than previously thought and that they can serve as a probe for dynamics that were previously considered out of reach.

After the PhD

I am currently a KICP fellow at the University of Chicago. I am continuing the work I developed during my PhD, with a special emphasis on observational aspects at the level of cosmic microwave backgrounds and more formal developments in the theoretical framework I explored during the late stages of my PhD. Among the projects of the first type, I am working on performing a more comprehensive analysis of well-understood paradigms at the theoretical level, but much less so at the observational level. In particular, I am analysing the set of theories developed during my PhD for special scenarios of the early universe. In the second type of project, I am working on understanding how to formally extend my PhD work to gravity and condensed matter. I have visited several US institutions, such as Caltech, Stanford, and UCSD, and I plan to have a career in academia.