@article{Graeter2020,
  author    = {Gr{\"a}ter, Joachim},
  title     = {Free division rings of fractions of crossed products of groups with Conradian left-orders},
  series = {Forum mathematicum},
  volume    = {32},
  journal   = {Forum mathematicum},
  number    = {3},
  publisher = {De Gruyter},
  address   = {Berlin},
  issn      = {0933-7741},
  doi       = {10.1515/forum-2019-0264},
  pages     = {739 -- 772},
  year      = {2020},
  abstract  = {Let D be a division ring of fractions of a crossed product F[G, eta, alpha], where F is a skew field and G is a group with Conradian left-order <=. For D we introduce the notion of freeness with respect to <= and show that D is free in this sense if and only if D can canonically be embedded into the endomorphism ring of the right F-vector space F((G)) of all formal power series in G over F with respect to <=. From this we obtain that all division rings of fractions of F[G, eta, alpha] which are free with respect to at least one Conradian left-order of G are isomorphic and that they are free with respect to any Conradian left-order of G. Moreover, F[G, eta, alpha] possesses a division ring of fraction which is free in this sense if and only if the rational closure of F[G, eta, alpha] in the endomorphism ring of the corresponding right F-vector space F((G)) is a skew field.},
  language  = {en}
}