Published online by Cambridge University Press: 24 May 2021
We develop methods for constructing explicit generators, modulo torsion, of the $K_3$-groups of imaginary quadratic number fields. These methods are based on either tessellations of hyperbolic
$3$-space or on direct calculations in suitable pre-Bloch groups and lead to the very first proven examples of explicit generators, modulo torsion, of any infinite
$K_3$-group of a number field. As part of this approach, we make several improvements to the theory of Bloch groups for
$ K_3 $ of any field, predict the precise power of
$2$ that should occur in the Lichtenbaum conjecture at
$ -1 $ and prove that this prediction is valid for all abelian number fields.