Brans–dicke Theory:  Jordan Versus Einstein Frame

Bhadra, Arunava; Sarkar, Kabita; Datta, Dilip; Nandi, K. K.

doi:10.1142/s021773230702261x

Cited by 49 publications

(55 citation statements)

References 31 publications

(46 reference statements)

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“…A viable cosmological model must accommodate all these features. Although the F(R) theory of gravity and its extended versions claim to have unified early inflation with late-time cosmic acceleration, this requires scalar-tensor equivalence at both ends [5][6][7], which might be misleading, since physical equivalence has been questioned over decades [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22]. An attempt of unification has been made with a non-minimally coupled dark energy model for the first time by Faraoni [23].…”

Section: Introductionmentioning

confidence: 99%

Unified cosmology with scalar–tensor theory of gravity

Tajahmad

Sanyal

2017

Eur. Phys. J. C

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Unlike the Noether symmetry, a metric independent general conserved current exists for non-minimally coupled scalar-tensor theory of gravity if the trace of the energymomentum tensor vanishes. Thus, in the context of cosmology, a symmetry exists both in the early vacuum and radiation dominated era. For slow roll, symmetry is sacrificed, but at the end of early inflation, such a symmetry leads to a Friedmann-like radiation era. Late-time cosmic acceleration in the matter dominated era is realized in the absence of symmetry, in view of the same decayed and redshifted scalar field. Thus, unification of early inflation with late-time cosmic acceleration with a single scalar field may be realized.

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Section: Introductionmentioning

confidence: 99%

Unified cosmology with scalar–tensor theory of gravity

Tajahmad

Sanyal

2017

Eur. Phys. J. C

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“…Scalar-tensor equivalence is a mathematical artifact, and it gives totally different quantum description [66] in comparison to one discussed earlier [62,63]. The difference at the classical level has also been established to some extent [67,68]. Thus, the prospect of ( ) theory of gravity appears to be at stake, unless one can find a better way out to handle the theory.…”

Section: On the Absence Of Noether Symmetry Andmentioning

confidence: 98%

Field Independent Cosmic Evolution

Sanyal

2013

Journal of Astrophysics

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It has been shown earlier that Noether symmetry does not admit a form of ( ) corresponding to an action in which ( ) is coupled to scalar-tensor theory of gravity or even for pure ( ) theory of gravity taking anisotropic model into account. Here, we prove that ( ) theory of gravity does not admit Noether symmetry even if it is coupled to tachyonic field and considering a gauge in addition. To handle such a theory, a general conserved current has been constructed under a condition which decouples higherorder curvature part from the field part. This condition, in principle, solves for the scale-factor independently. Thus, cosmological evolution remains independent of the form of the chosen field, whether it is a scalar or a tachyon.

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“…Singularity theorems and energy conditions have been studied in connection with Brans-Dicke theory, perhaps the most popular scalar-tensor gravity theories. However, their meaning remains still controversial due to the question of whether or not the Einstein frame and the Jordan frame are physically equivalent [37,38]. In the present geometrical approach, this controversy does not arise, as the physical entities defined in the theory are naturally invariant under frame transformations [39][40][41][42] (Table 2).…”

Section: Final Remarksmentioning

confidence: 99%