Geometry without Topology

Abstract

The proper Euclidean geometry is considered to be metric space and described in terms of only metric and finite metric subspaces (sigma-immanent description). Constructing the geometry, one does not use topology and topological properties. For instance, the straight, passing through points A and B, is defined as a set of such points R that the area S(A,B,R) of the triangle ABR vanishes. The triangle area is expressed via metric by means of the Hero's formula, and the straight appears to be defined only via metric, i.e. without a reference to (topological) concept of curve. (Usually the straight is defined as the shortest curve, connecting two points A and B). Such a construction of geometry is free from constraints (continuity, dimensionality of space), generated by a use of topology, but not by geometry in itself. At such a description all information on the geometry properties (such as uniformity, isotropy, continuity and degeneracy) is contained in metric. Modifying the metric, one changes the geometry automatically. The Riemannian geometry is constructed by two different ways: (1) by conventional way on the basis of metric tensor, (2) as a result of modification of the metric in the sigma-immanent description of the proper Euclidean geometry. The two obtained geometries are compared. The convexity problem in geometry and the problem of collinerity of vectors at distant points are considered. The nonmetric definition of curve is shown to be a concept of only proper Euclidean geometry. It is inadequate to any non-Euclidean geometry.