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

Dynamical models of string fluids are constructed from the general energy-m omentum tensor for string fluids in general relativity and the Einstein-Car tan 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-mome ntum tensor of Letelier. Solutions to the field equations in Riemann-Cartan spacetimes are compared with an extended Letelier solution. All calculatio ns are given for both the standard and the extended thermodynamics versions in which the latter includes the string as thermodynamic variables. In gen eral relativity, it is shown for black hole solutions that the general feat ure of strings (through the string vector) is to produce a shrinkage of the black hole horizon. In Riemann-Cartan spacetimes, the torsion field equati on shows that string vector can be identified with the torsion vector. The most striking feature of strings in Riemann-Cartan spacetimes is that in th e Reissner-Nordstrom solution, the addition of torsional strings produces t he correct asympototic behavior of the metric necessary to match the experi mental galactic rotation curves.