In this paper , the cosmic microwave background ( CMB ) anisotropy in a multiply-connected compact flat 3-torus model with the cosmological constant is investigated .
Using the COBE-DMR 4-year data , a full Bayesian analysis revealed that the constraint on the topology of the flat 3-torus model with low-matter-density is less stringent .
As in compact hyperbolic models , the large-angle temperature fluctuations can be produced as the gravitational potential decays at the \Lambda -dominant epoch well after the last scattering .
The maximum allowed number N of images of the cell ( fundamental domain ) within the observable region at present is approximately 49 for \Omega _ { m } = 0.1 and \Omega _ { \Lambda } = 0.9 whereas N \sim 8 for \Omega _ { m } = 1.0 and \Omega _ { \Lambda } = 0 .