We obtain new results for consistent braneworld Kaluza-Klein reductions, showing how we can derive four-dimensional N = 2 gauged supergravity " localised on the AdS 4 brane " as an exact embedding in five-dimensional N = 4 gauged supergravity. Similarly, we obtain five-dimensional N = 2 gauged supergravity localised on an AdS 5 brane as a consistent Kaluza-Klein reduction from six-dimensional N...

We consider fluid perturbations close to the ‘‘phantom divide’’ characterized by p and discuss the conditions under which divergencies in the perturbations can be avoided. We find that the behavior of the perturbations depends crucially on the prescription for the pressure perturbation p. The pressure perturbation is usually defined using the dark energy rest-frame, but we show that this frame ...

Some braneworld models may have observable consequences that, if detected, would validate a requisite element of string theory. In the infinite Randall-Sundrum model (RS2), the AdS radius of curvature, l, of the extra dimension supports a single bound state of the massless graviton on the brane, thereby reproducing Newtonian gravity in the weak-field limit. However, using the AdS/CFT correspond...

Observations exploring the contemporary cosmic acceleration have sparked interest in dark energy models possessing equations of state with w < −1. We review how the cosmic expansion history of a Dvali–Gabadadze–Porrati (DGP) braneworld model with a standard brane cosmological constant can mimic that of ordinary 4–dimensional gravity with w < −1 “phantom” dark energy for observationally relevant...

In this work we investigate a braneworld scenario where a Kalb-Ramond field propagates, together with gravity, in a five dimensional AdS slice. The rank-2 Kalb-Ramond field is associated with torsion. We study the compactification of the Kalb-Ramond field to four dimensional space-time without gauge fixing, focusing on the effects of torsion. On the brane the Kalb-Ramond field interacts with Aμ...

Observations exploring the contemporary cosmic acceleration have sparked interest in dark energy models possessing equations of state with w < −1. We review how the cosmic expansion history of a Dvali–Gabadadze–Porrati (DGP) braneworld model with a standard brane cosmological constant can mimic that of ordinary 4–dimensional gravity with w < −1 “phantom” dark energy for observationally relevant...

We consider a single Minkowski brane sandwiched in between two copies of anti-de Sitter space. We allow the bulk Planck mass and cosmological constant to differ on either side of the brane. Linearised perturbations about this background reveal that gravity can be modified in the infra-red. At intermediate scales, the braneworld propagator mimics four-dimensional GR in that it has the correct mo...

Braneworld models of dark energy are examined in the light of observations of high redshift type Ia supernovae. Braneworld models admit several novel and even exotic possibilities which include: (i) The effective equation of state of dark energy can be more negative than in LCDM: w ≤ −1; (ii) A class of braneworld models can encounter a ‘quiescent’ future singularity at which the energy density...

We propose a cosmological braneworld scenario in which two branes collide and emerge as reborn branes whose tensions have signs opposite to the original tensions of the respective branes. In this scenario, gravity on each of the branes is described by a scalar-tensor-type theory in which the radion plays the role of the gravitational scalar, and the branes are assumed to be inflating. However, ...

We study tunneling of massless and massive particles through the smeared quantum horizon of the extra-dimensional Schwarzschild black holes. The emission rate of the particles’ tunneling is modified by noncommutativity effects in a bulk spacetime of dimension d. The issues of information loss and possible correlations between emitted particles are discussed. We show that even by considering bot...