Cross-ratio: algebraic and topological approaches.

Angela Maria SITTA

Hermes Antônio PEDROSO^{1}

Wilson Maurício TADINI

- ABSTRACT:
_{1}, x_{2}, x_{3}, x_{4}), where x_{i}¹ x_{j}, 1 £ i, j £ 4, i ¹ j, the cross-ratio may assume up to six different values according to the ordering. We present the topology and the density of the subset in such that their points satisfy the following property: they assume six values, distinct two-by-two. - KEYWORDS: Cross-ratio, topology..