Forecasts of redshift drift constraints on cosmological parameters

ABSTRACT Cosmological observations usually map our present-day past light cone. However, it is also possible to compare different past light cones. This is the concept behind the redshift drift, a model-independent probe of fundamental cosmology. In simple physical terms, this effectively allows us to watch the Universe expand in real time. While current facilities only allow sensitivities several orders of magnitude worse than the expected signal, it should be possible to detect it with forthcoming ones. Here, we discuss the potential impact of measurements by three such facilities: the Extremely Large Telescope (the subject of most existing redshift drift forecasts), but also the Square Kilometre Array and intensity mapping experiments. For each of these we assume the measurement sensitivities estimated respectively in Liske et al. (2008), Klockner et al. (2015), and Yu, Zhang & Pen (2014). We focus on the role of these measurements in constraining dark energy scenarios, highlighting the fact that although on their own they yield comparatively weak constraints, they do probe regions of parameter space that are typically different from those probed by other experiments, as well as being redshift dependent. Specifically, we quantify how combinations of several redshift drift measurements at different redshifts, or combinations of redshift drift measurements with those from other canonical cosmological probes, can constrain some representative dark energy models. Our conclusion is that a model-independent mapping of the expansion of the universe from redshift z = 0 to z = 4 – a challenging but feasible goal for the next generation of astrophysical facilities – can have a significant impact on fundamental cosmology.

Towards a More Well-Founded Cosmology

First, this paper broaches the definition of science and the epistemic yield of tenets and approaches: phenomenological (descriptive only), well founded (solid first principles, conducive to deep understanding), provisional (falsifiable if universal, verifiable if existential), and imaginary (fictitious entities or processes, conducive to empirically unsupported beliefs). The Big Bang paradigm and the ΛCDM ‘concordance model’ involve such beliefs: the emanation of the universe out of a non-physical stage, cosmic inflation (hardly testable), Λ (fictitious energy), and ‘exotic’ dark matter. They fail in the confidence check that empirical science requires. They also face a problem in delimiting what expands from what does not. In the more well-founded cosmology that emerges, energy is conserved, the universe is persistent (not transient), and the ‘perfect cosmological principle’ holds. Waves and other field perturbations that propagate at c (the escape velocity of the universe) expand exponentially with distance. This results from gravitation. The galaxy web does not expand. Potential Φ varies as −H/(cz) instead of −1/r. Inertial forces reflect gradients present in comoving frames of accelerated bodies (interaction with the rest of the universe – not with space). They are increased where the universe appears blue-shifted and decreased more than proportionately at very low accelerations. A cut-off acceleration a0 = 0.168 cH is deduced. This explains the successful description of galaxy rotation curves by “Modified Newtonian Dynamics”. A fully elaborated physical theory is still pending. The recycling of energy via a cosmic ocean filled with photons (the cosmic microwave background), neutrinos and gravitons, and the wider implications for science are briefly discussed.

The Origin of Dark Energy and Cosmic Expansion and Contraction

<p class="1Body">This article proves that the photons of lower energy are annihilated into dark energy due to the destructive interference of light, and the increase of dark energy makes the universe expand, the Hubble formula could be derived based on it. The energy level of matter reduces, more and more matter becomes the dark matter in the process. The universe stops expanding and starts to contract in the action of gravity when the energy density of radiation field becomes small enough in it.</p>

HOW DOES THE UNIVERSE EXPAND?

Quantization of gravity suggests that a finite region of space has a finite number of degrees of freedom or 'bits'. What happens to these bits when spacetime expands, as in cosmological evolution? Using gravity/field theory duality we argue that bits 'fuse together' when space expands.