Constraining quantum initial conditions before inflation

We theoretically and observationally investigate different choices of initial conditions for the primordial mode function that are imposed during an epoch preceding inflation. By deriving predictions observables resulting from several alternate quantum vacuum prescriptions we show some vacua distinguishable others. Comparing these to Planck 2018 observations via a Bayesian analysis shows no significant evidence favor any over In addition consider frozen conditions, representing white-noise state at big-bang singularity. Under certain assumptions cosmological concordance model found produce identical cosmic microwave background anisotropies. Frozen may thus provide alternative theoretic paradigm explain were previously understood in terms inflation vacuum.