Comparison of string fluid dynamical models in general relativity and Einstein-Cartan theory

Dynamical models of string fluids are constructed from the general energy-momentum tensor for string fluids in general relativity and the Einstein-Cartan theories obtained from the Ray-Hilbert variational principle. Examples of solutions to the field equations for general relativistic spacetimes are given and compared with solutions obtained from the postulated energy-momentum tensor of Letelier. Solutions to the field equations in Riemann-Cartan spacetimes are compared with an extended Letelier solution. All calculations are given for both the standard and the extended thermodynamics versions in which the latter includes the string as thermodynamic variables. In general relativity, it is shown for black hole solutions that the general feature of strings (through the string vector) is to produce a shrinkage of the black hole horizon. In Riemann-Cartan spacetimes, the torsion field equation shows that string vector can be identified with the torsion vector. The most striking feature of strings in Riemann-Cartan spacetimes is that in the Reissner-Nordstrom solution, the addition of torsional strings produces the correct asympototic behavior of the metric necessary to match the experimental galactic rotation curves.