Covariant Energy-momentum Tensor Research Articles

Chiral torsional effects in anomalous fluids in thermal equilibrium

Using the similarity between spacetime torsion and axial gauge couplings, we study torsional contributions to the equilibrium partition function in a stationary background. In the case of a charged fluid minimally coupled to torsion, we spot the existence of linear torsional magnetic and vortical effects, while the axial-vector current and the spin energy potential do not receive corrections in the torsion at linear order. The covariant energy-momentum tensor, on the other hand, does contain terms linear in the torsion tensor. The case of a two-flavor hadronic superfluid is also analyzed, and the torsional contributions to the constitutive relations computed. Our results show the existence of a torsional electric chiral effect mediated by the charged pions.

Mathbf {O}(D,D) completion of the Friedmann equations

In string theory the closed-string massless NS-NS sector forms a multiplet of mathbf {O}(D,D) symmetry. This suggests a specific modification to General Relativity in which the entire NS-NS sector is promoted to stringy graviton fields. Imposing off-shell mathbf {O}(D,D) symmetry fixes the correct couplings to other matter fields and the Einstein field equations are enriched to comprise D^{2}+1 components, dubbed recently as the Einstein Double Field Equations. Here we explore the cosmological implications of this framework. We derive the most general homogeneous and isotropic ansatzes for both stringy graviton fields and the mathbf {O}(D,D)-covariant energy-momentum tensor. Crucially, the former admits space-filling magnetic H-flux. Substituting them into the Einstein Double Field Equations, we obtain the mathbf {O}(D,D) completion of the Friedmann equations along with a generalized continuity equation. We discuss how solutions in this framework may be characterized by two equation-of-state parameters, w and lambda , where the latter characterizes the relative intensities of scalar and tensor forces. When lambda +3w=1, the dilaton remains constant throughout the cosmological evolution, and one recovers the standard Friedmann equations for generic matter content (i.e. for any w). We further point out that, in contrast to General Relativity, neither an mathbf {O}(D,D)-symmetric cosmological constant nor a scalar field with positive energy density gives rise to a de Sitter solution.

Heat kernel approach to the relations between covariant and consistent currents in chiral gauge theories

We apply the heat kernel method to relations between covariant and consistent currents in anomalous chiral gauge theories. Banerjee et al. have shown that the relation between these currents is expressed by a "functional curl" of the covariant current. Using the heat kernel method, we evaluate the functional curl explicitly in arbitrary even dimensions. We also apply the heat kernel method to evaluate Osabe and Suzuki's results of the difference between covariant and consistent currents in two and four dimensions. Applying the arguments of Banerjee et al. to gravitational anomalies, we investigate the relationship between the covariant and consistent energy-momentum tensors. The relation is found to be expressed by a functional curl of the covariant energy-momentum tensor.

An almost Einsteinian theory of gravitation

A new version of relativistic theory of gravitation is proposed, in which the GR is supplemented with two postulates. Owing to these postulates it turns possible to introduce into consideration a covariant energy-momentum tensor of gravitational field. Additionally the influence of Universe on the gravitating system under consideration is taken into account. The equations describing the gravitation field in the framework of proposed tensor mono-metric theory of gravitation are derived. In its simplest version the proposed theory contains nine free parameters. At a particular choice of these parameters the theory is reduced to GR with a cosmological term.

Hydrodynamics in 1+1 dimensions with gravitational anomalies

The constraints imposed on hydrodynamics by the structure of gauge and gravitational anomalies are studied in two dimensions. By explicit integration of the consistent gravitational anomaly, we derive the equilibrium partition function at second derivative order. This partition function is then used to compute the parity-violating part of the covariant energy-momentum tensor and the transport coefficients.

Anomalies, Hawking Radiation in Taub-NUT Black Hole

In this paper, we mainly investigate the anomalous effective action of the rotating Taub-NUT black hole and show that the flux of Hawking radiation can be determined by anomaly cancellation conditions and regularity requirement at the event horizon. With the method of a dimensional reduction technique, that is, the (1+1) dimensional quantum anomalies equation, we successfully obtain the simplified metric near the horizon. In addition, the covariant energy-momentum tensor that is related with Hawking temperature are calculated in this black hole.

Hawking Radiation from NUT Kerr Newman Kusuya Black Hole via Effective Action and Covariant Anomalies

Using the theory of the anomalous (chiral) effective action and covariant anomalies method, the Hawking radiation from NUT-Kerr-Newman-Kusuya black hole is researched. In this paper, the electric charge parameter and magnetic monopole parameter are rewritten as equivalent parameter. In addition, we simplify the metric as 1+1 dimensional effective metric. Finally, with the method of anomalous effective action and covariant anomalies respectively, we calculate the chiral covariant current and covariant energy-momentum tensor.

Hawking radiation from black holes in de Sitter spaces via covariant anomalies

We apply the covariant anomaly cancellation method to compute the Hawking fluxes from the event and cosmic horizons of the Schwarzschild–de Sitter black hole. The derivation is new from the existing ones as we split the space in three different regions (near to and away from the event and cosmic horizons) and write down the covariant energy–momentum tensor using three step functions which covers the whole region leading elegantly to the conditions required to compute the Hawking fluxes from the event and cosmic horizons.

Energy-Momentum of a Cosmological Brane Model and the Gauge Hierarchy

We analyze in this paper the general covariant energy-momentum tensor of the gravitational system in general five-dimensional cosmological brane-world models. Then through calculating this energy-momentum for the cosmological generalization of the Randall-Sundrum model, which includes the original RS model as the static limit, we are able to show that the weakness of the gravitation on the “visible” brane is a general feature of this model. This is the origin of the gauge hierarchy from a gravitational point of view. Our results are also consistent with the fact that a gravitational system has vanishing total energy.

A covariant gravitational field equation including the contribution of gravitational field

Using the four-leg metric tensor λ(α)μ, a gravitational field 4-vector potential for index μ is defined as ω(α)μ≡-cλ(α)μ, and a covariant gravitational field equation that includes the gravitational field contribution is proposed as Rμν-gμνR/2+Λgμν=8πG(T(Ⅰ)μν+T(Ⅱ)μν)/c4, where Λ is Einstein's cosmic constant， T(Ⅰ)μν and T(Ⅱ)μν are energy-momentum tensor of pure matter part and pure gravitational field part, respectively. The covariant energy-momentum tensor of gravitational field that belongs to the part of the gravitational source can be constructed as T(Ⅱ)μν=c2(D(α)μρDρν(α)-gμνD(α)τγDτγ(α)/4)/4πG, where D(α)μν≡ω(α)μ;ν-ω(α)ν;μ. The static spherically symmetric gravitational field, the missing mass and the gravitational field quantization are discussed.

Conformally Covariant Theory of Second Rank Antisymmetric Tensor Field

The conformally covariant field equation on second rank antisymmetric tensor is derived and its conformally covariant energy-momentum tensor is also obtained.

On the Conformally Covariant Energy-Momentum Tensor

A method is proposed with which one can easily obtain the conformally covariant energy-momentum tensors for various fields from the canonical ones.

New type of vacuum solutions of nonlinear conformally covariant coupled field equations

A six-parameter family of new solutions of conformally covariant nonlinear coupled scalar and spinor field equations is given for which the conformally covariant energy-momentum tensor vanishes. The previously known solutions are special cases of this family of solutions.

Derivation and uniqueness of vacuum solutions of conformally covariant coupled nonlinear field equations

We derive the solutions of conformally covariant coupled Dirac and scalar fields including a nonlinear fermion self-coupling term for which the conformally covariant (not the canonical, nor the symmetric) energy-momentum tensor θ μν vanishes. This “vacuum” state is degenerate.

On the general expression of the conformally covariant energy-momentum tensor

Derives a general expression of the conformally covariant energy-momentum tensor by starting from the general form of the Lagrangian from which the field equations are conformally covariant. The conformal group consists of inhomogeneous Lorentz transformations, dilatation transformations, and special conformal transformations.

On the conformal covariant energy-momentum tensor

In a conformal symmetric theory the author proposes a conformal covariant energy-momentum tensor, in terms of which other conformal currents are expressed.

On the energy-momentum tensor of the gravitional field

In a previous note it was suggested that x-1Λgμν, with Λ>0 fulfills the basic requirements of a generally covariant energy-momentum tensor for the gravitational field. Some further justification is given for this hypothesis bya) studying the character of the field equations in the absence of the cosmological term;b) a re-interpretation of the line element based on Mach’s principle;c) calculating the gravitational proper energy for de Sitter static universe with and without a Schwarzschild field present and showing that the difference is proportional to the Schwarzschild mass. Finally an attempt is made to define a true tensor for the angular momentum density. It is shown that in this way one is led to a definition of « physical co-ordinates ». These co-ordinates are determined in such a way that in the weak-field limit they approach the usual Lorentz co-ordinates. However it is not possible to arrive at these co-ordinates by imposing co-ordinate conditions, since they form the components of a vector. To the extent that the angular momentum of the gravitational field is covariantly conserved, the co-ordinates may be obtained as the gradient of a world scalar which satisfies an inhomogeneous d’Alembertian equation.