Skew-symmetric massless fields, their potentials being r-forms, are close analogues of Maxwell's field (though the nonlinear cases also should be considered). We observe that only two of them (r = 2 and 3) automatically yield stress-energy tensors characteristic of normal perfect fluids. It is shown that they naturally describe both nonrotating (r = 2) and rotating general relativistic perfect fluids (then a combination of r = 2 and r = 3 fields is indispensable) and possess every type of equation of state. Meanwhile, a free r = 3 field is completely equivalent to the appearance of the cosmological term in Einstein's equations. Sound waves represent perturbations propagating on the background of the r = 2 field. Some exotic properties of these two fields are outlined. [References: 23]
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