DR. TEJASWI NERALLA

Mapping neutral hydrogen at high redshifts using the 21-cm line is one of the next big observational frontiers in cosmology. Its main advantage is that it provides three dimensional information, which provides access to many more modes than the Cosmic Microwave Background does. The speaker will highlight another feature of the line that makes it possible to extract even more interesting cosmological information from high-resolution 21-cm observations, when they are realized in the future. This is the spin-degeneracy of the triplet excited state of the transition. In this talk, the speaker will outline how the 21-cm line's brightness temperature fluctuations encode information about magnetic fields that are coherent on large scales in the early universe. This technique will be naturally sensitive to extremely weak field strengths of order 10-19 G, which opens the possibility of probing primordial magnetic fields in neutral gas prior to reionization. He will also briefly touch upon the exciting, if even more speculative possibility of studying primordial gravitational waves using the 21cm line.