Effective Dark-Energy Density from Residual Shear After a Bounce: Two Normalisations, Two Verdicts

Residual shear from a bounce is sometimes suggested as a dark-energy source. Shear, however, carries the equation of state of a stiff component, not of a cosmological constant, and its density dilutes as the sixth power of the inverse scale factor. This paper evaluates both possible normalisations. Fixed at the bounce, the shear density today is negligible. Fixed instead to equal the observed dark-energy density today, the same component at nucleosynthesis exceeds the total density then allowed by an enormous factor and would have prevented the observed light-element pattern. The component also has the wrong pressure sign for acceleration at any normalisation. Residual shear is therefore excluded as the dark energy in this frame, on grounds of both magnitude history and equation of state. Headline values are: shear today fraction 0p01 kg m3 = 7.431e-114, ratio bbn if today normalised = 7.442e+21, w shear = 1.0, dilution factor = 7.647e-170. This study is simulated and computed from stated assumptions; it is not a measurement.