scholarly journals A NONSTATIC PLANE-SYMMETRIC SOLUTION OF EINSTEIN EQUATIONS WITH A SPECIAL SCALAR FIELD

1993 ◽  
Vol 42 (2) ◽  
pp. 188
Author(s):  
LI JIAN-ZENG

1970 ◽  
Vol 20 (9) ◽  
pp. 1053-1054
Author(s):  
J. Horský ◽  
M. Lenc


Author(s):  
D. D. Pawar ◽  
S. P. Shahare ◽  
Y. S. Solanke ◽  
V. J. Dagwal


1992 ◽  
Vol 07 (27) ◽  
pp. 2463-2467 ◽  
Author(s):  
SUBENOY CHAKRABORTY

Wormhole solutions are discussed for two different physical situations in the background of a homogeneous anisotropic space-time. In the first case, the wormholes are solutions of the Euclidean Einstein equations with a cosmological constant and a two-index anti-symmetric tensor for monopole configuration on a space with three-surface of topology S1×S2. In the second step, conformal scalar field is coupled to gravity and wormhole are considered for both λ=0 and λ>0. These results are analogous to the wormhole solutions for FRW metric.



2000 ◽  
Vol 15 (36) ◽  
pp. 2205-2218 ◽  
Author(s):  
A. SOLOVYOV

We consider (2+1)-dimensional classical noncommutative scalar field theory. The general ansatz for a radially symmetric solution is obtained. Some exact solutions are presented. Their possible physical meaning is discussed. The case of finite θ is discussed qualitatively and illustrated by some numerical results.







2022 ◽  
Vol 08 (01) ◽  
pp. 164-177
Author(s):  
Arnaud Edouard Yamadjako ◽  
Alain Adomou ◽  
Yélomè J. F. Kpomahou ◽  
Jonas Edou ◽  
Siaka Massou


2020 ◽  
Vol 80 (9) ◽  
Author(s):  
John D. Barrow ◽  
Spiros Cotsakis

AbstractWe generalise Einstein’s formulation of the traceless Einstein equations to f(R) gravity theories. In the case of the vacuum traceless Einstein equations, we show that a non-constant Weyl tensor leads via a conformal transformation to a dimensionally homogeneous (‘no-scale’) theory in the conformal frame with a scalar field source that has an exponential potential. We then formulate the traceless version of f(R) gravity, and we find that a conformal transformation leads to a no-scale theory conformally equivalent to general relativity and a scalar field $$\phi $$ ϕ with a potential given by the scale-invariant form: $$V(\phi )=\frac{D-2}{4D}Re^{-\phi }$$ V ( ϕ ) = D - 2 4 D R e - ϕ , where $$\phi =[2/(D-2)]\ln f^{\prime }(R)$$ ϕ = [ 2 / ( D - 2 ) ] ln f ′ ( R ) . In this theory, the cosmological constant is a mere integration constant, statistically distributed in a multiverse of independent causal domains, the vacuum energy is another unrelated arbitrary constant, and the same is true of the height of the inflationary plateau present in a huge variety of potentials. Unlike in the conformal equivalent of full general relativity, flat potentials are found to be possible in all spacetime dimensions for polynomial lagrangians of all orders. Hence, we are led to a novel interpretation of the cosmological constant vacuum energy problem and have accelerated inflationary expansion in the very early universe with a very small cosmological constant at late times for a wide range of no-scale theories. Fine-tunings required in traceless general relativity or standard non-traceless f(R) theories of gravity are avoided. We show that the predictions of the scale-invariant conformal potential are completely consistent with microwave background observational data concerning the primordial tilt and the tensor-to-scalar ratio.



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