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1
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Discrete Space-Time by Means of the Weyl-Dirac Theory

100%
Agop M., Chicos L., Gîrţu M.
Acta Physica Polonica A
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2007
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vol. 112
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issue 1
3-12
EN
A connection between the Weyl-Dirac theory and scale relativity theory through the hydrodynamic models (relativistic and non-relativistic approaches) is established. In such conjecture, considering that the motions of the microparticles take place on continuous but non-differentiable curves i.e. on fractals, a Weyl-Dirac type equation was found. Some correspondences with known hydrodynamic models, particularly Białynicki-Birula's approach, are analyzed. All these results reflect the fractal structure of the space-time (a concept in agreement with the new ideas on the space-time)
2
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Super-energy and Killing-Yano tensors

80%
Tintareanu-Mircea O., Popa F.
Open Physics
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2005
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vol. 3
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issue 2
258-269
EN
In this paper we investigate a class of basic super-energy tensors, namely those constructed from Killing-Yano tensors, and give a generalization of super-energy tensors for cases when we start not with a single tensor, but with a pair of tensors.
3
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Wormhole Solution and Energy in Teleparallel Theory of Gravity

80%
Nashed G.
Acta Physica Polonica A
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2007
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vol. 111
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issue 2
201-213
EN
An exact solution is obtained in the tetrad theory of gravitation. This solution is characterized by two parameters k_1, k_2 of spherically symmetric static Lorentzian wormhole which is obtained as a solution of the equation ρ= ρ_t=0 with ρ=T_{i,j}u^iu^j, ρ_t =(T_{ij}-1/2Tg_{ij}) u^iu^j, where u^iu_i=-1. From this solution which contains an arbitrary function we can generate the other two solutions obtained before. The associated metric of this space-time is a static Lorentzian wormhole and it includes the Schwarzschild black hole, a family of naked singularity and a disjoint family of Lorentzian wormholes. Calculating the energy content of this tetrad field and using the gravitational energy momentum given by Møller in the teleparallel space-time we find that the resulting form depends on the arbitrary function and does not depend on the two parameters k_1 and k_2 characterizing the wormhole. Using the regularized expression of the gravitational energy momentum we get the value of energy which does not depend on the arbitrary function.
4
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Stability of Reissner-Nordström Black Hole

80%
Nashed G.
Acta Physica Polonica A
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2007
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vol. 112
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issue 1
13-21
EN
The singularity of the solutions obtained before in the teleparallel theory of gravitation is studied. Also the stability of these solutions is studied using the equations of geodesic deviation. The condition of stability is obtained. From this condition the stability of the Schwarzschild solution can be obtained.
5
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Centrifugal (centripetal) and Coriolis' velocities and accelerations in $$ (\bar L_n ,g) $$ -spaces

51%
Manoff S.
Open Physics
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2003
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vol. 1
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issue 4
669-694
EN
The notions of centrifugal (centripetal) and Coriolis' velocities and accelerations are introduced and considered in spaces with affine connections and metrics [ $$ (\bar L_n ,g) $$ -spaces] as velocities and accelerations of flows of mass elements (particles) moving in space-time. It is shown that these types of velocities and accelerations are generated by the relative motions between the mass elements. They are closely related to the kinematic characteristics of the relative velocity and relative acceleration. The centrifugal (centripetal) velocity is found to be in connection with the Hubble law. The centrifugal (centripetal) acceleration could be interpreted as gravitational acceleration as has been done in the Einstein theory of gravitation. This fact could be used as a basis for workingout new gravitational theories in spaces with affine connections and metrics.
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