Options for cosmology at redshifts above one

Abstract

We show that detailed exploration of the $1<z<2$ redshift region can provide for definitive testing not only of the standard inflationary cosmological paradigm with its fine-tuned cosmological constant and its mysteriously late ($z<1$) onset of cosmic acceleration, but also for the non fine-tuned, alternate conformal cosmological model, a cosmology which accelerates both above and below $z=1$. In particular we confront both of these models with the currently available type Ia supernovae standard candle and extended FRII radio source standard yardstick data, with these latter data being particularly pertinent as they already include a sizeable number of points in the $1<z<2$ region. We find that both models are able to account for all available $0<z<2$ data equally well; and with the conformal model explicitly being able to fit the data while being an accelerating one in the $z>1$ region, one is thus currently unable to ascertain whether the universe is accelerating or decelerating between $z=1$ and $z=2$. To be able to visualize the supernovae and radio galaxy data simultaneously, we present a representation of the radio galaxy data in terms of an equivalent apparent magnitude Hubble diagram. We discuss briefly some implications of the anisotropies in the cosmic microwave background for the conformal theory, and show that in that theory fluctuations which set in at around nucleosynthesis can readily generate the first peak in the anisotropy data.