Studying the initial condition of the universe

Abstract:

The exponential expansion of the universe in the first infinitesimal fraction of time, called cosmic inflation, converts the quantum fluctuations into initial conditions for the large-scale structure that we observe and live in today. Inflation thereby imprints dynamics of the earliest of times on observations of the largest scales, such as the cosmic microwave background (CMB) and distribution of galaxies. With developments in theory and observations in tandem for more than four decades, the sky map of the current universe has turned into a laboratory to inspect physical phenomena of the primordial universe. Particularly in the last decade, several new phenomena, such as the generation of primordial black holes and non-trivial gravitational waves (GW), have garnered the attention of inflationary theorists. In this talk, I shall briefly outline inflation as a paradigm for generating primordial perturbations. I shall illustrate it using certain models that lead to unique imprints in the above-mentioned observables. I shall then focus on an interesting aspect of breaking parity during inflation. Violation of parity in nature is well-known and leads to birefringence and chirality in optical systems. If parity is violated during inflation, it can induce chirality in GW. I shall discuss a specific mechanism of parity-violation which produces GW with preferential helicity, which ongoing and upcoming observational missions, such as the pulsar timing array can detect.

All are cordially invited.