Convergence of scalar–tensor theories towards general relativity and primordial nucleosynthesis

Serna, A.; Alimi, Jean‐Michel; Navarro, A.

doi:10.1088/0264-9381/19/5/302

Cited by 39 publications

(79 citation statements)

References 29 publications

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“…Although the action (1) describes correctly what can be observed in the presence of an abnormally weighting sector, this Dicke − Jordan observable frame somehow hide the underlying theory of gravitation due to the admixture of scalar and tensor degrees of freedom and is consequently not convenient for studying the dynamics of the gravitational coupling Φ [22]. It is therefore insightful to rewrite action (1) in the so-called Einstein frame where the tensorialg µν and scalar Φ gravitational degrees of freedom separate into a bare metric g µν and a screening field ϕ.…”

Section: Cosmological Dynamics In Tensor-scalar Anomalous Gravitymentioning

confidence: 99%

The abnormally weighting energy hypothesis: the missing link between dark matter and dark energy

Alimi

Füzfa

2008

J. Cosmol. Astropart. Phys.

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Abstract. We generalize tensor-scalar theories of gravitation by the introduction of an abnormally weighting type of energy. This theory of tensor-scalar anomalous gravity is based on a relaxation of the weak equivalence principle that is now restricted to ordinary visible matter only. As a consequence, the convergence mechanism toward general relativity is modified and produces naturally cosmic acceleration as an inescapable gravitational feedback induced by the mass-variation of some invisible sector. The cosmological implications of this new theoretical framework are studied. From the Hubble diagram cosmological test alone, this theory provides an estimation of the amount of baryons and dark matter in the Universe that is consistent with the independent cosmological tests of Cosmic Microwave Background (CMB) and Big Bang Nucleosynthesis (BBN). Cosmic coincidence is naturally achieved from a equally natural assumption on the amplitude of the scalar coupling strength. Finally, from the adequacy to supernovae data, we derive a new intriguing relation between the spacetime dependences of the gravitational coupling and the dark matter mass, providing an example of crucial constraint on microphysics from cosmology. This glimpses at an enticing new symmetry between the visible and invisible sectors, namely that the scalar charges of visible and invisible matter are exactly opposite.

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Section: Cosmological Dynamics In Tensor-scalar Anomalous Gravitymentioning

confidence: 99%

The abnormally weighting energy hypothesis: the missing link between dark matter and dark energy

Alimi

Füzfa

2008

J. Cosmol. Astropart. Phys.

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“…In the Jordan frame this amounts to defining a new time variable, dp = h c dt ≡ H +Ψ 2Ψ dt , and deriving from Eqs. (2)- (4) a "master" equation for the scalar field [15,16]. It can be written in a form of a dynamical system for variables Ψ ≡ x, Ψ ′ ≡ z (f ′ ≡ df /dp)…”

Section: Fixed Points For Matter Domination (Vmentioning

confidence: 99%

Scalar-Tensor Cosmologies: General Relativity as a Fixed Point of the Jordan Frame Scalar Field

Kuusk

Järv

Saal

2009

Int. J. Mod. Phys. A

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We study the evolution of homogeneous and isotropic, flat cosmological models within the general scalar-tensor theory of gravity with arbitrary coupling function and potential and scrutinize its limit to general relativity. Using the methods of dynamical systems for the decoupled equation of the Jordan frame scalar field we find the fixed points of flows in two cases: potential domination and matter domination. We present the conditions on the mathematical form of the coupling function and potential which determine the nature of the fixed points (attractor or other). There are two types of fixed points, both are characterized by cosmological evolution mimicking general relativity, but only one of the types is compatible with the Solar System PPN constraints.

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“…A possible candidate for dark energy can therefore be an AWE type of matter which has recently altered the well-known convergence mechanism toward general relativity during the matter-dominated epoch (Damour & Nordtvedt 1993 ;Serna, Alimi & Navarro 2002) due to its violation of the WEP. Such a recent modification of GR can result in an accelerated expansion and a variation of the gravitational constant.…”

Section: An Awe Born-infeld Gauge Interactionmentioning

confidence: 99%

Is Dark Energy Abnormally Weighting?

Alimi

Füzfa

2009

From Quantum to Cosmos

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Abstract. We present a new interpretation of dark energy in terms of an Abnormally Weighting Energy (AWE). This means that dark energy does not couple to gravitation in the same way as ordinary matter, yielding a violation of the weak and strong equivalence principles on cosmological scales. The resulting cosmological mechanism accounts for the Hubble diagram of type Ia supernovae in terms of both cosmic acceleration and variation of the gravitational constant while still accounting for the present tests of general relativity. This explanation allows to build dark energy models (i) without violation of the strong energy condition p < −ρc 2 /3 (ii) with non-negligible direct couplings to gravitation and (iii) natural convergence mechanism toward general relativity. Motivations for an abnormally weighting energyMaybe the most helpful astrophysical evidence for determining the nature of dark energy is the dimmed magnitude of type Ia supernovae (see Astier et al. 2006 and references therein). This tell us that either the recent cosmic expansion has accelerated or (and) these objects are not standard candles, which could have happened if, for instance, fundamental constants of physics have recently varied. This is the first explanation that is retained in the so-called concordance model ΛCDM in which a positive cosmological constant constitutes the dark energy sector of cosmology. This convenient explanation does not require to give up neither general relativity (GR) nor the cosmological principle and furthermore allows to account for dark energy effects with only one additional parameter. However, the cosmological constant is usually interpreted as the stress-energy term associated to the vacuum state which has non-vanishing energy due to quantum fluctuations. Doing so, one recovers the old problem of the overestimation of the cosmological constant. Indeed, if one assumes that the cut-off energy scale at which GR is no longer valid is the Planck length, then the vacuum energy density acting as a cosmological constant is ρ Λ ≈ m 4 P l ≈ 10 76 GeV 4 (in geometrical units whereh = c = 1, G = m −2 P l ). Which mechanism can be so precise to make such a huge quantity vanishing? This constitutes the so-called fine-tuning problem of the cosmological constant. What is worst now with the astrophysical evidences for the cosmological constant, is that the vacuum energy density is indeed not vanishing but is of cosmological order of magnitude:We have therefore a huge disagreement between theory and experiment of more than 120 orders of magnitude! Why is the vacuum energy density, something that should be set once for all in the universe and should depend on quantum mechanics, is of the order of the critical density today? Such a value suggests a cosmological mechanism behind the value of the cosmological constant... Even worst, this means that we live in a very particular epoch in the history of the universe : the time when the cosmological constant, whose value has a priori nothing to do with cosmology if it is fixed by quantu...

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Convergence of scalar–tensor theories towards general relativity and primordial nucleosynthesis

Cited by 39 publications

References 29 publications

The abnormally weighting energy hypothesis: the missing link between dark matter and dark energy

The abnormally weighting energy hypothesis: the missing link between dark matter and dark energy

Scalar-Tensor Cosmologies: General Relativity as a Fixed Point of the Jordan Frame Scalar Field

Is Dark Energy Abnormally Weighting?

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