Restrictions on Dilatonic Brane-World Models

We investigate four-dimensional effective theories which are obtained by dimensional reduction of multidimensional cosmological models with factorizable geometry and consider the interaction between conformal excitations of the internal space (geometrical moduli excitations) and Abelian gauge fields. It is assumed that the internal space background can be stabilized by minima of an effective potential. The conformal excitations over such a background have the form of massive scalar fields (gravitational excitons) propagating in the external spacetime. We discuss cosmological and astrophysical implications of the interaction between gravexcitons and four-dimensional photons as well as constraints arising on multidimensional models of the type considered in our paper. In particular, we show that due to the experimental bounds on the variation of the fine structure constant, gravexcitons should decay before nucleosynthesis starts. For a successful nucleosynthesis the masses of the decaying gravexcitons should be m > ∼ 10 4 GeV. Furthermore, we discuss the possible contribution of gravexcitons to UHECR. It is shown that, at energies E ∼ 10 20 eV, the decay length of gravexcitons with masses m > ∼ 10 4 GeV is very small, but that for m < ∼ 10 2 GeV it becomes much larger than the Greisen-Zatsepin-Kuzmin cut-off distance. Finally, we investigate the possibility for gravexciton-photon oscillations in strong magnetic fields of astrophysical objects. The corresponding estimates indicate that even the high magnetic field strengths B of magnetars (special types of pulsars with B > B critical ∼ 4.4 × 10 13 Gauss) are not sufficient for an efficient and copious production of gravexcitons.

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“…Brane-world models with on-brane dilatonic coupling terms have been considered, e.g., in Refs [44,45]…”

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confidence: 99%

Multidimensional cosmological models: Cosmological and astrophysical implications and constraints

2004

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“…It means that Λ ef f > 0, J 11 > 0 and J 22 > 0. From the positivity of J 11 and Λ ef f we obtain respectively 5 : 5 It is interesting to note that (in the case D 0 = d 1 = 4) rela-and Λ ef f > 0 : h > R 1 /16 > U 0 (X)/9 > h/3 > 0 .…”

Section: Decoupling Of Excitations: D1 = D0mentioning

confidence: 80%

“…(see e.g. [5]- [9]) and references therein). There are strong experimental bounds on such variations [10].…”

Section: Introductionmentioning

confidence: 99%

1/Rmultidimensional gravity with form-fields: Stabilization of extra dimensions, cosmic acceleration, and domain walls

Saidov

Zhuk

2007

Phys. Rev. D

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We study multidimensional gravitational models with scalar curvature nonlinearity of the type 1/R and with form-fields (fluxes) as a matter source. It is assumed that the higher dimensional spacetime undergoes Freund-Rubin-like spontaneous compactification to a warped product manifold. It is shown that for certain parameter regions the model allows for a freezing stabilization of the internal space near the positive minimum of the effective potential which plays the role of the positive cosmological constant. This cosmological constant provides the observable late-time accelerating expansion of the Universe if parameters of the model is fine tuned. Additionally, the effective potential has the saddle point. It results in domain walls in the Universe. We show that these domain walls do not undergo inflation.

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“…The field ψ could be associated with geometrical moduli. In brane-world models the similar term describes an interaction between the bulk dilaton and the Standard Model fields on the brane [14]. In Ref.…”

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confidence: 99%

“…Eq. (3) together with Bianchi identity (which is preserved in the considered model due to gaugeinvariance of the tensor, F µν [17]) defines a complete set 1 In the brane-world model the prefactor κ 0 in the expression for κ 0 ψ is replaced by the parameter proportional to M −1 EW [14]. Thus, the smallness condition holds for ψ < M EW .…”

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confidence: 99%

Extra dimensions and Lorentz invariance violation

2007

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We consider effective model where photons interact with scalar field corresponding to conformal excitations of the internal space (geometrical moduli/gravexcitons). We demonstrate that this interaction results in a modified dispersion relation for photons, and consequently, the photon group velocity depends on the energy implying the propagation time delay effect. We suggest to use the experimental bounds of the time delay of gamma ray bursts (GRBs) photons propagation as an additional constrain for the gravexciton parameters.PACS numbers: 04.50.+h, 11.25.Mj, Lorentz invariance (LI) of physical laws is one of the corner stone of modern physics. There is a number of experiments confirming this symmetry at energies we can approach now. For example, on a classical level, the rotation invariance has been tested in Michelson-Morley experiments, and the boost invariance has been tested in Kennedy-Torhndike experiments [1]. Although, up to now, LI is well established experimentally, we cannot say surely that at higher energies it is still valid. Moreover, modern astrophysical and cosmological data (e.g. UHECR, dark matter, dark energy, etc) indicate for a possible LI violation (LV). To resolve these challenges, there are number of attempts to create new physical models, such as M/string theory, Kaluza-Klein models, brane-world models, etc. [1].In this paper we investigate LV test related to photon dispersion measure (PhDM). This test is based on the LV effect of a phenomenological energy-dependent speed of photon [2,3,4,5,6,7,8], for recent studies see Ref.[9] and references therein.The formalism that we use is based on the analogy with electromagnetic waves propagation in a magnetized medium, and extends previous works [8,10,11]. In our model, instead of propagation in a magnetized medium, the electromagnetic waves are propagating in vacuum filled with a scalar field ψ. LV occurs because of an interaction term f(ψ)F 2 where F is an amplitude of the electromagnetic field. Such an interaction might have different origins. In the string theory ψ could be a dilaton field [12,13]. The field ψ could be associated with geometrical moduli. In brane-world models the similar term describes an interaction between the bulk dilaton and the Standard Model fields on the brane [14]. In Ref.[15], such an interaction was obtained in N = 4 * Electronic address: bauch˙vGR@ukr.net † Electronic address: zhuk@paco.net ‡ Electronic address: tinatin@phys.ksu.edu super-gravity in four dimensions. In Kaluza-Klein models the term f(ψ)F 2 has the pure geometrical origin, and it appears in the effective, dimensionally reduced, four dimensional action (see e.g. [16,17]). In particular, in reduced Einstein-Yang-Mills theories, the function f (ψ) coincides (up to a numerical prefactor) with the volume of the internal space. Phenomenological (exactly solvable) models with spherical symmetries were considered in Refs. [18]. To be more specific, we consider the model which is based on the reduced Einstein-Yang-Mills theory [17], where the term ∝ ψF 2 de...

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Restrictions on Dilatonic Brane-World Models

Cited by 5 publications

References 29 publications

Multidimensional cosmological models: Cosmological and astrophysical implications and constraints

Multidimensional cosmological models: Cosmological and astrophysical implications and constraints

1/Rmultidimensional gravity with form-fields: Stabilization of extra dimensions, cosmic acceleration, and domain walls

Extra dimensions and Lorentz invariance violation

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