We investigate the line element of spacetime around a linear cosmic string in
the presence of a cosmological constant. We obtain the metric and argue that it
should be discarded because of asymptotic considerations. Then a time dependent
and consistent form of the metric is obtained and its properties are discussed.Comment: 3 page
Abstract. Multiple field models of inflation exhibit new features than single field models.In this work, we study the hierarchy of parameters based on Hubble expansion rate in curved field space and derive the system of flow equations that describe their evolutions. Then we focus on obtaining derivatives of number of e-folds with respect to scalar fields during inflation and at hypersurface of the end of inflation.
In this paper, we elaborate the problem of energy-momentum in GR by energy-momentum prescriptions theory. In this regard, we calculate Møller, Landau-Lifshitz, Papapetrou, Einstein, Bergmann, Tolman, and Weinberg's energy-momentum complexes in static and non-static cosmic string space-times. We obtain strong coincidences between the results. These coincidences can be considered as an extension of Virbhadra's viewpoint that different energy-momentum prescriptions may provide some basis to define a unique quantity. In addition, our results disagree with Lessner's belief about Møller's prescription, and support the Virbhadra's conclusion about power of Einstein's prescription.
In the present study, we consider general form of the Lagrangian f (R, φ I , X), that is a function of the Ricci scalar, multiple scalar fields and non-canonical kinetic terms. We obtain the effective Newton's constant deep inside the Hubble radius. We use Jordan and Einstein frames, and study the conservation of energy-momentum tensor.
Einstein, Landau-Lifshitz, Papapetrou, Weinberg, and Møller energy-momentum prescriptions in general spherically symmetric space-times are investigated. It is shown that for two special but not unusual classes of general spherically symmetric space-times several energy-momentum prescriptions in Schwarzschild Cartesian coordinates lead to some coincidences in energy distribution. It is also obtained that for a special class of spherically symmetric metrics Møller and Einstein energymomentum prescriptions give the same result for energy distribution if and only if it has a specific dependence on radial coordinate.
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