Perfect Fluids: Field-theoretical Description and Gauge Symmetry Issue

We show that combinations of (in general,non-linear) two- and threeform fields, analogous to theMaxwell (one-form) field, completely describe perfectfluids, including the rotating ones. In the non-rotating case, the two-form field is sufficient, and afree three-form field proves to be equivalent toappearance of the cosmological term in Einstein'sequations (the square-root non-linearity correspondingto = 0). The gauge degrees of freedombreak down when a rotation is included, but even whenthey exist, there fails to be realized an equivalence ofthe two-form field and the massless scalar one recently claimed by Weinberg.     

Spinless Matter in Transposed-Equi-Affine Theory of Gravity

We derive and discuss the equations of motion for spinless matter: relativistic spinless scalar fields, particles and fluids in the model of gravity recently proposed by A. Saa with covariantly constant volume with respect to the transposed connection in Einstein-Cartan spaces. A new interpretation of this theory as a theory with variable Planck constant is suggested. We show that the consistency of the semiclassical limit of the wave equation and classical motion dictates a new definite universal interaction of torsion with massive fields.     

Comparison of String Fluid Dynamical Models in General Relativity and Einstein–Cartan theory

Dynamical models of string fluids areconstructed from the general energy-momentum tensor forstring fluids in general relativity and theEinstein-Cartan theories obtained from the Ray-Hilbertvariational principle. Examples of solutions to the fieldequations for general relativistic spacetimes are givenand compared with solutions obtained from the postulatedenergy-momentum tensor of Letelier. Solutions to the field equations in Riemann-Cartanspacetimes are compared with an extended Leteliersolution. All calculations are given for both thestandard and the extended thermodynamics versions inwhich the latter includes the string as thermodynamicvariables. In general relativity, it is shown for blackhole solutions that the general feature of strings(through the string vector) is to produce a shrinkage of the black hole horizon. In RiemannCartanspacetimes, the torsion field equation shows that stringvector can be identified with the torsion vector. Themost striking feature of strings in Riemann-Cartan spacetimes is that in the Reissner-Nordstromsolution, the addition of torsional strings produces thecorrect asympototic behavior of the metric necessary tomatch the experimental galactic rotationcurves.     

OBTAINING THE CRITICAL DRAW RATIO OF DRAW RESONANCE IN MELT SPINNING FOR POWER LAW POLYMER FLUIDS

A direct difference method has been developed for Non-Newtonian power law fluids to solve the simultaneous non-linear partial differential equations of melt spinning,and to determine the critical draw ratio for draw resonance.The results show that for shear thin fluids,the logarithm of the critical draw ratio has a well defined linear relationship with the power index for isothermal and uniform tension melt spinning.When the power index approaches zero,the critical draw ratio points at unity,indicating no melt spinning can be processed stably for such fluids.For shear thick fluids,the critical draw ratio increases in a more rapid way with increasing the power index.