Second order formalism in Poincare gauge theory

Changing the set of independent variables of Poincare gauge theory and considering, in a manner similar to the second order formalism of general relativity, the Riemannian part of the Lorentz connection as function of the tetrad field, we construct theories that do not contain second or higher order derivatives in the field variables, possess a full general relativity limit in the absence of spinning matter fields, and allow for propagating torsion fields in the general case. A concrete model is discussed and the field equations are reduced by means of a Yasskin type ansatz to a conventional Einstein-Proca system. Approximate solutions describing the exterior of a spin polarized neutron star are prsented and the possibility of an experimental detection of the torsion fields is briefly discussed.Comment: final version, to appear in IJMP

One-parameter teleparallel limit of Poincare gravity

Poincare gauge theories that, in the absence of spinning matter, reduce to the one-parameter teleparallel theory are investigated with respect to their mathematical consistency and experimental viability. It is argued that the theories can be consistently coupled to the known standard model particles. Moreover, we establish the result that in the classical limit, such theories share a large class of solutions with general relativity, containing, among others, the four classical black hole solutions (Schwarzschild, Reisner-Nordstrom, Kerr and Kerr-Newman), as well as the complete class of Friedman-Robertson-Walker cosmological solutions, thereby extending older viability results that were restricted to the correct Newtonian limit and to the existence of the Schwarzschild solution.Comment: 8 pages, revtex4, accepted for publication in Phys. Rev.