‎the object of the present paper is to study spacetimes admitting‎ ‎quasi-conformal curvature tensor‎. ‎at first we prove that a quasi-conformally flat spacetime is einstein‎ ‎and hence it is of constant curvature and the energy momentum tensor of such a spacetime satisfying‎ ‎einstein's field equation with cosmological constant is covariant constant‎. ‎next‎, ‎we prove that if the perfect...

‎The object of the present paper is to study spacetimes admitting‎ ‎quasi-conformal curvature tensor‎. ‎At first we prove that a quasi-conformally flat spacetime is Einstein‎ ‎and hence it is of constant curvature and the energy momentum tensor of such a spacetime satisfying‎ ‎Einstein's field equation with cosmological constant is covariant constant‎. ‎Next‎, ‎we prove that if the perfect flui...

wewanttofindthecosmologicalconstantinfluenceoncosmicmicrowavebackground(cmb)temperatureduetomovinglinearcosmicstrings.usingthespace-timemetricofalinearcosmicstringinanacceleratedexpandinguniverse,thegott-kaiser stebbins(gks)effect,asanimportantmechanisminproducingtemperaturediscontinuityinthe(cmb),isconsidered;then,itsmodificationduetotheeffectofthecosmologicalconstantiscalculated.theresultshowsthat...

We prove that a class of one-loop partition functions found by Dienes, giving rise to a vanishing cosmological constant to one-loop, cannot be realized by a consistent lattice string. The construction of non-supersymmetric string with a vanishing cosmological constant therefore remains as elusive as ever. We also discuss a new test that any one-loop partition function for a lattice string must ...