Gauss-Bonnet Braneworld Research Articles

Modified large distance Newton potential on a Gauss-Bonnet brane world

Gravity on a brane world with higher order curvature terms and a conformally coupled bulk scalar field is investigated. Solutions with non-standard large distance gravity are described. It is not necessary to include a scalar field potential in order to obtain the solutions. The resulting Newton potential is qualitatively similar to that of the Dvali-Gabadadze-Porrati (DGP) model. For suitable parameter choices the model is ghost free. Like many other brane gravity models with modified large distance Newton potentials, the short distance gravity is scalar-tensor. The scalar couples with gravitational strength, and so the model is not compatible with observation.

Gravitational baryogenesis in Gauss-Bonnet braneworld cosmology

The mechanism of gravitational baryogenesis, based on the CPT-violating gravitational interaction between the derivative of the Ricci scalar curvature and the baryon-number current, is investigated in the context of the Gauss-Bonnet braneworld cosmology. We study the constraints on the fundamental five-dimensional gravity scale, the effective scale of B-violation and the decoupling temperature, for the above mechanism to generate an acceptable baryon asymmetry during the radiation-dominated era. The scenario of gravitational leptogenesis, where the lepton-number violating interactions are associated with the neutrino mass seesaw operator, is also considered.

Inflation parameters from Gauss–Bonnet braneworld

We calculate the spectral index and tensor-to-scalar ratio for patch inflation arisen from the Gauss–Bonnet braneworld scenario. The patch cosmological models consist of Gauss–Bonnet (GB), Randall–Sundrum (RS), and 4D general relativistic (GR) cases. In order to compare with the observation data, we perform leading-order calculations for all patch models by choosing large-field, small-field, and hybrid potentials. We show that the large-field potentials are sensitive to a given patch model, while the small-field and hybrid potentials are insensitive to a given patch model. It is easier to discriminates between quadratic potential and quartic potential in the GB model rather than RS and GR models. Irrespective of patch models, it turns out that the small-field potentials are the promising models in view of the observation.

Effective actions of a Gauss–Bonnet brane world with brane curvature terms

We consider a warped brane world scenario with two branes, Gauss–Bonnet gravity in the bulk, and brane localised curvature terms. When matter is present on both branes, we investigate the linear equations of motion and distinguish three regimes. At very high energy and for an observer on the positive tension brane, gravity is four-dimensional and coupled to the brane bending mode in a Brans–Dicke fashion. The coupling to matter and brane bending on the negative tension brane is exponentially suppressed. In an intermediate regime, gravity appears to be five dimensional while the brane bending mode remains four-dimensional. At low energy, matter on both branes couple to gravity for an observer on the positive tension brane, with a Brans–Dicke description similar to the 2-brane Randall–Sundrum setup. We also consider the zero mode truncation at low energy and show that the moduli approximation fails to reproduce the low energy action.

Cosmological constraints on inflation potential: the role of Gauss–Bonnet corrections inbraneworld scenarios

We calculate the spectral index and tensor-to-scalar ratio for patch inflation defined by and , using the slow-roll expansion. The patch cosmology arising from the Gauss–Bonnetbraneworld consists of Gauss–Bonnet (GB), Randall–Sundrum (RS), and 4D generalrelativistic (GR) cosmological models. In this work, we choose large-field potentials ofV = V0ϕp to compare with the observational data. Since second-order corrections are rather small inthe slow-roll limit, the leading-order calculation is sufficient to compare with the data.Finally, we show that it is easier to discriminate between a quadratic potential and quarticpotential in the GB cosmological model rather than the GR or RS cosmological models.

Observational constraints on patch inflation in noncommutative spacetime

We study constraints on a number of patch inflationary models in noncommutative spacetime using a compilation of recent high-precision observational data. In particular, the four-dimensional General Relativistic (GR) case, the Randall-Sundrum (RS) and Gauss-Bonnet (GB) braneworld scenarios are investigated by extending previous commutative analyses to the infrared limit of a maximally symmetric realization of the stringy uncertainty principle. The effect of spacetime noncommutativity modifies the standard consistency relation between the tensor spectral index and the tensor-to-scalar ratio. We perform likelihood analyses in terms of inflationary observables using new consistency relations and confront them with large-field inflationary models with potential V \propto \vp^p in two classes of noncommutative scenarios. We find a number of interesting results: (i) the quartic potential (p=4) is rescued from marginal rejection in the class 2 GR case, and (ii) steep inflation driven by an exponential potential (p \to \infty) is allowed in the class 1 RS case. Spacetime noncommutativity can lead to blue-tilted scalar and tensor spectra even for monomial potentials, thus opening up a possibility to explain the loss of power observed in the cosmic microwave background anisotropies. We also explore patch inflation with a Dirac-Born-Infeld tachyon field and explicitly show that the associated likelihood analysis is equivalent to the one in the ordinary scalar field case by using horizon-flow parameters. It turns out that tachyon inflation is compatible with observations in all patch cosmologies even for large p.

Generalized Israel junction conditions for a Gauss-Bonnet brane world

In spacetimes of dimension greater than four it is natural to consider higher order (in $R)$ corrections to the Einstein equations. In this paper generalized Israel junction conditions for a membrane in such a theory are derived. This is achieved by generalizing the Gibbons-Hawking boundary term. The junction conditions are applied to simple brane world models, and are compared to the many contradictory results in the literature.