摘要
We have pointed out that on the principles of special relativity and of propagation of light going along the null geodesic the special relativity of Einstein can be extented to the 3-dimensional Beltrami space-time D_λ with constant curvaturesλ<0, λ= 0 and λ>0. The inertial coordinate systems for each of them are so-called Beltrami coordinates and their metrics are also Beltrami
