Parity asymmetry of primordial scalar and tensor power spectra

Abstract: Although the cosmic microwave background (CMB) is largely understood to be homogeneous and isotropic, the CMB angular power spectra present anomalies that seem to break down parity symmetry at large angular scales. We argue that the primordial scalar and tensor power spectra can be parity asymmetric in our new construction of inflationary quantum fluctuations. Our formulation stems from the foundational questions of quantum field theory in curved spacetime in which we impose geometric superselection rules to the vacuum structure for (single-field) inflationary quantum fluctuations based on discrete spacetime transformations ($\mathcal{P}\mathcal{T}$). As a result, we estimate the amplitude of power asymmetry in the scalar and tensor sectors at different scales of $ 10^{-4} {\rm Mpc^{-1}}\lesssim k\lesssim 10^{-3}{\rm Mpc^{-1}}$. In particular, we predict the parity asymmetry for the primordial gravitational waves (PGWs) and quantify it for different models, like Starobinsky and $\alpha-$attractor single-field inflationary scenarios.