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Janusz Garecki

Publications and source records attributed to Janusz Garecki.

30 records · Page 2Linked to original sources
arXiv2006

The averaged tensors of the relative energy-momentum and angular momentum in general relativity and some their applications

There exist at least a few different kind of averaging of the differences of the energy-momentum and angular momentum in normal coordinates {\bf NC(P)} which give tensorial quantities. The obtained averaged quantities are equivalent mathematically because they differ only by constant scalar dimensional factors. One of these averaging was used in our papers [1-8] giving the {\it canonical superenergy and angular supermomentum tensors}. In this paper we present another averaging of the differences of the energy-momentum and angular momentum which gives tensorial quantities with proper dimensions of the energy-momentum and angular momentum densities. But these averaged relative energy-momentum and angular momentum tensors, closely related to the canonical superenergy and angular supermomentum tensors, {\it depend on some fundamental length $L>0$}. The averaged relative energy-momentum and angular momentum tensors of the gravitational field obtained in the paper can be applied, like the canonical superenergy and angular supermomentum tensors, to {\it coordinate independent} analysis (local and in special cases also global) of this field. We have applied the averaged relative energy-momentum tensors to analyze vacuum gravitational energy and momentum and to analyze energy and momentum of the Friedman (and also more general) universes. The obtained results are very interesting, e.g., the averaged relative energy density is {\it positive definite} for the all Friedman universes.

gr-qc↗
arXiv2005

The averaged tensors of the relative energy-momentum and angular momentum in general relativity

There exist at least a few different kind of averaging of the differences of the energy-momentum and angular momentum in normal coordinates {\bf NC(P)} which give tensorial quantities. The obtained averaged quantities are equivalent mathematically because they differ only by constant scalar dimensional factors. One of these averaging was used in our papers [1-8] giving the {\it canonical superenergy and angular supermomentum tensors}. In this paper we present one other averaging of the energy-momentum and angular momentum differences which gives tensorial quantities with proper dimensions of the energy-momentum and angular momentum densities. But these averaged energy-momentum and angular momentum tensors, closely related to the canonical superenergy and angular supermomentum tensors, {\it depend on some fundamental length L}. The averaged energy-momentum and angular momentum tensors of the gravitational field obtained in the paper can be applied, like the canonical superenergy and angular supermomentum tensors, to coordinate independent local (and also global) analysis of this field.

gr-qc↗
arXiv2005

On the gravitational energy of the Bonnor spacetime

In the paper we consider the energy and its flux in the Bonnor spacetime. We construct some non-local expressions from the Einstein canonical energy-momentum pseudotensor of the gravitational field which show that the gravitational energy and its flux in this spacetime are different from zero and do not vanish even outside of the material source (a stationary beam of the null dust) of this spacetime.

gr-qc↗
arXiv2004

Energy-momentum and angular momentum of Goedel universes

We discuss the Einstein energy-momentum complex and the Bergmann-Thomson angular momentum complex in general relativity and calculate them for space-time homogeneous Goedel universes. The calculations are performed for a dust acausal model and for a scalar-field causal model. It is shown that the Einstein pseudotensor is traceless, not symmetric, the gravitational energy is "density" is negative and the gravitational Poynting vector vanishes. Significantly, the total (gravitational and matter) energy "density" fro the acausal model is zero while for the casual model it is negative.The Bergmann-Thomson angular momentum complex does not vanish for both Gödel models.

gr-qc↗
arXiv2003

On Hypothesis of the Two Large Extradimensions

Recently there was proposeda hypothesis about existence of the two large extradimensions. This hypothesis demands, e.g., modification of Newton law at submilimeter scale. In this brief report we show that this hypothesis cannot be correct in presen formulation.

gr-qc↗
arXiv2002

Einsteinian Strengths and Dynamical Degrees of Freedom for Alternative Gravity Theories

In this paper we present the results of our calculations of the Einsteinian strengths S_E(d) and numbers dynamical degrees of freedom N_{DF}(d) for alternative gravity theories in d >= 4 dimensions. In the first part we consider the numbers S_E(d) and N_{DF}(d) for metric-compatible and quadratic in curvature (or quadratic in curvature and in torsion) gravity. We show that in the entire set of the metric-compatible quadratic gravity in d >= 4 dimensions the 2-nd order Einstein-Gauss-Bonnet theory has the smallest numbers S_E(d) and N_{DF}(d), i.e., this quadratic theory of gravity has the strongest field equations. From the physical point of view this theory is the best one quadratic and metric-compatible theory of gravity in d >= 4 dimensions.

gr-qc↗
arXiv2002

A Possible Test for Quadratic Gravity in $d \ge 4$ dimensions

In this letter we consider the Einsteinian strengths and dynamical degrees of freedom for quadratic gravity. We show that purely metric quadratic gravity theories are much stronger in Einsteinian sense than the competitive quadratic gravity theories which admit torsion.

gr-qc↗
arXiv2001

Superenergy and Supermomentum of Goedel Universes

We review the canonical superenergy tensor and the canonical angular supermomentum tensors in general relativity and calculate them for space-time homogeneous Gödel universes to show that both of these tensors do not, in general, vanish. We consider both an original dust-filled pressureless acausal Gödel model of 1949 and a scalar-field-filled causal Gödel model of Rebou\c cas and Tiomno. For the acausal model, the non-vanishing components of superenergy of matter are different from those of gravitation. The angular supermomentum tensors of matter and gravitation do not vanish either which simply reflects the fact that Gödel universe rotates. However, the axial (totally antisymmetric) and vectorial parts of supermomentum tensors vanish. It is interesting that superenergetic quantities are {\it sensitive} to causality in a way that superenergy density $_g S_{00}$ of gravitation in the acausal model is {\it positive}, while superenergy density $_g S_{00}$ in the causal model is {\it negative}. That means superenergetic quantities might serve as criterion of causality in cosmology and prove useful.

gr-qc↗
arXiv2001

Is torsion needed in theory of gravity?

It is known that General Relativity ({\bf GR}) uses Lorentzian Manifold $(M_4;g)$ as a geometrical model of the physical space-time. $M_4$ means here a four-dimensional differentiable manifold endowed with Lorentzian metric $g$. The metric $g$ satisfies Einstein equations. Since the 1970s many authors have tried to generalize this geometrical model of the physical space-time by introducing torsion and even more general metric-affine geometry. In this paper we discuss status of torsion in the theory of gravity. At first, we emphasize that up to now we have no experimental evidence for the existence of torsion in Nature. Contrary, the all experiments performed in weak gravitational field (Solar System) or in strong regime (binary pulsars) and tests of the Einstein Equivalence Principle ({\bf EEP}) confirmed {\bf GR} and Lorentzian manifold $(M_4;g)$ as correct geometrical model of the physical space-time. Then, we give theoretical arguments against introducing of torsion into geometrical model of the physical space-time. At last, we conclude that the general-relativistic model of the physical space-time is sufficient and it seems to be the most satisfactory.

gr-qc↗
arXiv2001

Remarks on the Bergmann-Thomsom Expression on Angular Momentum in General Relativity

Often it is asserted that only by using of the symmetric Landau-Lifschitz energy-momentum complex one is able to formulate a conserved angular momentum complex in General Relativity ({\bf GR}). Obviously, it is an uncorrect statement. For example, years ago, Bergmann and Thomson have given other, very useful expression on angular momentum. This expression is closely joined to the non-symmetric, Einstein canonical energy-momentum complex. In the paper we review the Bergmann-Thomson angular momentum complex and compare it with that of given by Landau and Lifschitz.

gr-qc↗
arXiv2000

Some remarks on the Bel-Robinson Tensor

In this paper we present our point of view on correct physical interpretation of the Bel-Robinson tensor within the framework of the standard General Relativity ({\bf GR}), i.e., within the framework of the {\bf GR} without supplementary elements like arbitrary vector field, distinguished tetrads field or second metric. We show that this tensor arises as a consequence of the Bianchi identities and, in a natural manner, it is linked to the differences of the canonical gravitational energy-momentum calculated in normal coordinates {\bf NC(P)}.

gr-qc↗