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Free keywords:
Astrophysics, astro-ph,General Relativity and Quantum Cosmology, gr-qc
Abstract:
In this paper we consider the relation between the volume deceleration
parameter obtained within the Buchert averaging scheme and the deceleration
parameter derived from the supernova observation. This work was motivated by
recent findings that showed that there are models which despite $\Lambda=0$
have volume deceleration parameter $q^{vol} < 0$. This opens the possibility
that backreaction and averaging effects may be used as an interesting
alternative explanation to the dark energy phenomenon.
We have calculated $q^{vol}$ in some Lema\^itre--Tolman models. For those
models which are chosen to be realistic and which fit the supernova data, we
find that $q^{vol} > 0$, while those models which we have been able to find
which exhibit $q^{vol} < 0$ turn out to be unrealistic. This indicates that
care must be exercised in relating the deceleration parameter to observations.
