Showing papers on "Four-tensor published in 1997"

Quantum effects in the Alcubierre warp-drive spacetime

Abstract: The expectation value of the stress - energy tensor of a free conformally invariant scalar field is computed in a two-dimensional reduction of the Alcubierre `warp-drive' spacetime. Unless the spacetime is in the Hartle - Hawking state at an appropriate temperature, the stress - energy diverges on past and future event horizons which form when the apparent velocity of the spaceship exceeds the speed of light. The likelihood of the spacetime being in this state, whether due to natural evolution or the application of technology, is briefly discussed.

On the properties of the Eshelly tensor

Abstract: The Eshelby tensor (also referred to as the Maxwell tensor of elasticity, or the energy momentum tensor of elasticity, or the material momentum tensor), is being widely used in contracted form (e.g., with the unit normal vector) in the study of defect and fracture mechanics, most prominently as the integrand of the path-independent J-integral. However, the properties and the physical interpretation of the components of this tensor itself have remained seemingly unexplored. This contribution attempts to remedy this situation and presents a rather detailed discussion of the features of this tensor in the context of linearized elasticity.

Jet observables and energy-momentum tensor

Abstract: We clarify and extend the theorem of Sveshnikov and Tkachov [hep-ph/9512370], which gives an explicit connection between jet observables and energy-momentum tensor. We check the relation between jet observables and energy-momentum tensor for non-scalar (spinor and vector) field, give a correct treatment of the light-cone singularity for massless particles, and extend the theorem to the massless case. We also discuss the issue of gauge invariance.

Tensor Expressions for Solving Einstein's Equations by the Method of Sequential Approximation

Abstract: The main aim of this paper is to develop a mathematical tool for General Relativity (GR). For this purpose useful tensor expressions have been worked out, which considerably ease various calculations using the sequential approximation in Einstein's GR. Based upon these expressions, compact and explicit formulae have been worked out for the covariant and contravariant components of the metric tensor and its determinant.

Energy-Momentum Tensor Valued Distributions for the Schwarzschild and Reissner-Nordstrom Geometries

Abstract: An approach to computing, withing the framework of distribution theory, the distributional valued energy-momentum tensor for the Schwarzschild spacetime is disscused. This approach avoids the problems associated with the regularization of singularities in the curvature tensors and shares common features with the by now standard treatment of discontinuities in General Relativity. Finally, the Reissner-Nordstrom spacetime is also considered using the same approach.

Stress-energy tensor of an electromagnetic field in Schwarzschild spacetime

Abstract: The approximate stress tensors of an electromagnetic field in the Unruh and Hartle-Hawking vacua in the Schwarzschild spacetime are constructed It is shown that by solving the conservation equation in conformal space and utilizing the regularity conditions in a physical metric one obtains the stress tensors that are in excellent agreement with the exact numerical calculations

Type N spacetimes whose invariant classifications require the fourth covariant derivative of the Riemann tensor

Abstract: We describe a pure radiation spacetime of Petrov type N whose invariant classification requires the fourth covariant derivative of the Riemann tensor. The spacetime is the first non-conformally flat example which exhibits this quality and shows that spacetimes with matter and non-zero Weyl tensor can also require high-order derivatives in their invariant classification.

Approximate stress tensor of massless scalar field for an evaporating black hole

Abstract: The approximate stress tensor of a massless, conformally invariant scalar field in the Unruh vacuum in the Schwarzschild spacetime is constructed. It satisfies all regularity and consistency conditions and properly reproduces exact numerical calculations.

Gauge Theory of Massive Tensor Field. II. Covariant Expressions.

Abstract: Covariant forms are given to a gauge theory of massive tensor field. This is accomplished by introducing another auxiliary field of scalar type to the system composed of a symmetric tensor field and an auxiliary field of vector type. The situation is compared to the case of the theory in which a tensor field describes a scalar ghost as well as an ordinary massive tensor. In this case only an auxiliary vector field is needed to give covariant expressions for the gauge theory.