Conserved quantities and the formation of black holes in the Brans-Dicke theory of gravitation

In Part I, we construct a symmetric stress-energy-momentum pseudo-tensor for the gravitational fields of Brans-Dicke theory, and use this to establish rigorously conserved integral expressions for energy-momentum Pⁱ and angular momentum J^ik. Application of the two-dimensional surface integrals to the exact static spherical vacuum solution of Brans leads to an identification of our conserved mass with the active gravitational mass. Application to the distant fields of an arbitrary stationary source reveals that Pⁱ and J^ik have the same physical interpretation as in general relativity. For gravitational waves whose wavelength is small on the scale of the background radius of curvature, averaging over several wavelengths in the Brill-Hartle-Isaacson manner produces a stress-energy-momentum tensor for gravitational radiation which may be used to calculate the changes in Pⁱ and J^ik of their source.

In Part II, we develop strong evidence in favor of a conjecture by Penrose--that, in the Brans-Dicke theory, relativistic gravitational collapse in three dimensions produce black holes identical to those of general relativity. After pointing out that any black hole solution of general relativity also satisfies Brans-Dicke theory, we establish the Schwarzschild and Kerr geometries as the only possible spherical and axially symmetric black hole exteriors, respectively. Also, we show that a Schwarzschild geometry is necessarily formed in the collapse of an uncharged sphere.

Appendices discuss relationships among relativistic gravity theories and an example of a theory in which black holes do not exist.

Gravitational constraints of dS branes in an AdS Einstein-Brans-Dicke bulk

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Brane cosmic string compactification in Brans-Dicke theory

We investigate an alternative compactification of extra dimensions using local cosmic string in the Brans-Dicke gravity framework. In the context of dynamical systems it is possible to show that there exist a stable field configuration for the Einstein-Brans-Dicke equations. We explore the analogies between this particular model and the Randall-Sundrum scenario.

Gauss-Codazzi formalism to brane-world within Brans-Dicke theory

We apply the Gauss-Codazzi formalism to brane-worlds within the framework of Brans-Dicke gravity. The compactification is taken from six to five dimensions in order to formalize brane-world models with hybrid compactification in scalar tensor theories.

Introdução à gravitação de Brans-Dicke

The cosmological standard model needs a deep improvement when compared to recent observational data and also when contrasted with a broad theorical context. Al- ternative theories to General Relativity are possible candidates to reach the expectation Physics of Elementary Particles and Gravitation. Scalar-tensor theories seem to reappear from the ashes of the old work by Jordan corresponding appropriately low power limits of unifying theories. Being the Brans Dicke theory a scalar tensor is conducted a comprehensive study starting from its rst motivations to it s current one it is re flections

Compactificação alternativa de dimensões extras em gravitação de Brans-Dicke

After a brief introduction of some gravitational aspects of the Randall-Sundrum braneworld model as well as of the Brans-Dicke (BD) gravity, we propose two braneworld models using the, local and global, cosmic strings in the BD framework in order to generate all the bulk/brane structure. The final scenario is composed, in both cases, of a warped 4-brane with topology 'R POT. 4' x 'S POT. 1' and one extra dimension transverse to the brane. After that, we analyze the founded models in the scope of the Gauss-Codazzi formalism, with and without the imposition of 'Z IND. 2' symmetry on the brane

On the consistency conditions to braneworlds in scalar-tensor gravity for arbitrary dimensions

We derive an one-parameter family of consistency conditions to braneworlds in the Brans-Dicke gravity. The General Relativity case is recovered by taking a correct limit of the Brans-Dicke parameter. We show that it is possible to build a multiple AdS brane scenario in a six-dimensional bulk only if the brane tensions are negative. Besides, in the five-dimensional case, it is showed that no fine tuning is necessary between the bulk cosmological constant and the brane tensions, in contrast to the Randall-Sundrum model. Copyright © owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial- ShareAlike Licence.

Um estudo sobre teorias de dimensões extras: modelos de branas geradas por campos escalares

In this work we study extra dimensional theories, taking emphasis in braneworld models generated by real scalar fields. Firstly, we revise the Randall-Sundrum models and we discuss about some thick braneworld scenarios already considered in the literature. We introduce a new thick brane model in order to address the Standard Model hierarchy problem. Furthermore, we show that there exists a class of scalar fields models which are very interesting for analytical studies of thick brane scenarios. Finally, we analyze the braneworld consistency conditions in the context of f(R) and Brans-Dicke gravities, where we show that it is possible to evade a no-go theorem regarding thick brane scenarios

Conformal invariance and scalar-tensor theories

A new generalisation of Einstein’s theory is proposed which is invariant under conformal mappings. Two scalar fields are introduced in addition to the metric tensor field, so that two special choices of gauge are available for physical interpretation, the ‘Einstein gauge’ and the ‘atomic gauge’. The theory is not unique but contains two adjustable parameters ζ anda. Witha=1 the theory viewed from the atomic gauge is Brans-Dicke theory (ω=−3/2+ζ/4). Any other choice ofa leads to a creation-field theory. In particular the theory given by the choicea=−3 possesses a cosmological solution satisfying Dirac’s ‘large numbers’ hypothesis.

A parity-violatingU4-gravitation theory

The general structure of a metric-torsion theory of gravitation allows a parity-violating contribution to the complete action which is linear in the curvature tensor and vanishes identically in the absence of torsion. The resulting action involves, apart from the constant ¯K E =8pgr/c4, a coupling (B) which governs the strength of the parity interaction mediated by torsion. In this model the Brans-Dicke scalar field generates the torsion field, even though it has zero spin. The interesting consequence of the theory is that its results for the solar-system differ very little from those obtained from Brans-Dicke (BD) theory. Therefore the theory is indistinguishable from BD theory in solar-system experiments.

A new theory of gravitation with parity-violating propagating torsion

A new theory of gravitation has been proposed in a more general space-time than Riemannian. It is a generalization of the ECSK and Brans-Dicke (BD) theory of gravitation. It is found that, in contrast to the standard the ECSK theory, a parity-violating propagating torsion is generated by the BD scalar field. The interesting consequence of the theory is that it can successfully predict solar system experimental results to desired accuracy.

Positive tension 3-branes in an AdS(5) bulk

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Non-Z(2) symmetric braneworlds in scalar tensorial gravity

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Towards a hybrid compactification with a scalar-tensor global cosmic string

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)