What do we know about cosmography
Abstract
In the present paper, we investigate the cosmographic problem using the biasvariance tradeoff. We find that both the zredshift and the y=z/(1+z)redshift can present a small bias estimation. It means that the cosmography can describe the supernova data more accurately. Minimizing risk, it suggests that cosmography up to the second order is the best approximation. Forecasting the constraint from future measurements, we find that future supernova and redshift drift can significantly improve the constraint, thus having the potential to solve the cosmographic problem. We also exploit the values of cosmography on the deceleration parameter and equation of state of dark energy w( z). We find that supernova cosmography cannot give stable estimations on them. However, much useful information was obtained, such as that the cosmography favors a complicated dark energy with varying w( z), and the derivative { {d}}w/{ {d}}z <0 for low redshift. The cosmography is helpful to model the dark energy.
 Publication:

European Physical Journal C
 Pub Date:
 July 2017
 DOI:
 10.1140/epjc/s1005201750054
 arXiv:
 arXiv:1601.01758
 Bibcode:
 2017EPJC...77..434Z
 Keywords:

 Astrophysics  Cosmology and Nongalactic Astrophysics
 EPrint:
 12 pages, 10 figures, 1 table, accepted by EPJC