Astrophysics, abstract
astro-ph/0602159

From: Boudewijn Roukema [view email]

Date: Tue, 7 Feb 2006 15:08:54 GMT (58kb)

A weak cosmological constant due to residual gravity in a multiply connected universe

Authors: Boudewijn F. Roukema (1), Stanislaw Bajtlik (2), Marek Biesiada (3), Agnieszka Szaniewska (1), Helena Jurkiewicz (1) ((1) Torun Centre for Astronomy, (2) CAMK, (3) University of Silesia)

Comments: 8 pages, 3 figures, submitted to Astronomy & Astrophysics

Two of the biggest open questions in physical cosmology are the physical interpretation of dark energy, and the still uncertain global shape of comoving space. It was previously shown that multiple connectedness, via the twin paradox of special relativity, provides physical justification for an otherwise arbitrary assumption of the standard FLRW model: it implies a favoured space-time splitting (comoving coordinates). Could cosmic topology also imply dark energy? We use a weak field approximation of gravity and consider the gravitational effect from distant, multiple copies of a large, collapsed object today, taking into account the finite propogation speed of gravity, in a flat, multiply connected universe, and assume that due to a prior epoch of fast expansion (e.g. inflation), the gravitational effect of the distant copies is felt locally, from beyond the naively calculated horizon. We find that the residual newtonian gravitational force provides an effect that repels test particles from the cluster, proportionally to the distance from the cluster. This effect is algebraically similar to that of a cosmological constant and could be interpreted as an effect repelling a test object at comoving distance \chi from the nearest dense nodes of the cosmic web of density perturbations. The amplitude of the effect, expressed in terms of the pressure-to-density ratio w in an FLRW universe, is w \sim -(\chi/L)^3, where L is the size of the fundamental domain. Clearly, |w|<<1. Provided that at least a modest amount of inflation occurred in the early Universe, and given some other conditions, multiple connectedness does generate an effect similar to that of dark energy, but the amplitude of the effect at the present epoch is too small to explain the observed dark energy density.

http://arxiv.org/abs/astro-ph/0602159