2016/03/31 by C. Sofia Carvalho, Spyros Basilakos
Physics and Astronomy · #astro-ph.CO
paper · pdf · doi:10.1051/0004-6361/201628572
published as A&A 592, A152 (2016) · 11 pages, 5 figures: Revised version to be published in A&A. arXiv admin note: text overlap with arXiv:1512.07869
arxiv created 2016/07/12 · arxiv updated 2016/08/24
We use a kinematic parametrisation of the luminosity distance to measure the angular distribution on the sky of time derivatives of the scale factor, in particular the Hubble parameter H0, the deceleration parameter q0, and the jerk parameter j0. We apply a recently published method to complement probing the inhomogeneity of the large-scale structure by means of the inhomogeneity in the cosmic expansion. This parametrisation is independent of the cosmological equation of state, which renders it adequate to test interpretations of the cosmic acceleration alternative to the cosmological constant. For the same analytical toy model of an inhomogeneous ensemble of homogenous pixels, we derive the backreaction term in j0 due to the fluctuations of H0,q0 and measure it to be of order 10-2 times the corresponding average over the pixels in the absence of backreaction. In agreement with that computed using a Lambda CDM parametrisation of the luminosity distance, the backreaction effect on q0 remains below the detection threshold. Although the backreaction effect on j0 is about ten times that on q0, it is also below the detection threshold. Hence backreaction remains unobservable both in q0 and in j0.