If two DGP branes carry U(1) gauge theories and overlap, particles of one brane can interact with the photons from the other brane. This coupling modifies in particular the Coulomb potentials between charges from the same brane in the overlapping regions. The coupling also introduces Coulomb interactions between charges from the different branes which can generate exotic bound states.
The effective modification of the fine structure constant in the overlap region generates a trough in signals at the redshift of the overlap region and an increase at smaller or larger redshift, depending on the value of the crosstalk parameter. This implies potentially observable perturbations in the Lyman-alpha forest if our 3-brane overlapped with another 3-brane in a region with redshift z<6. Crosstalk can also affect structure formation by enhancing or suppressing radiative cooling.
We analyse a DGP brane filled with a k-essence field and assume the k-field evolving linearly with the cosmic time of the brane. We then solve analytically the Friedmann equation and deduce the different behaviour of the brane at the low and the high energy regimes. The asymptotic behaviour can be quite different involving accelerating branes, big bangs, big crunches, big rips or quiescent singularities. The latter correspond to a type of sudden singularity.
In this paper, the cosmological dynamics of a modified holographic dark energy which is derived from the UV/IR duality by considering the black hole mass in higher dimensions as UV cutoff, is investigated in Dvali-Gabadaze-Porrati (DGP) brane world model. We choose Hubble horizon and future event horizon as IR cutoff respectively. And the two branches of the DGP model are both taken into account. When Hubble horizon is considered as IR cutoff, the modified holographic dark energy (HDE) behaves like an effect dark energy that modification of gravity in pure DGP brane world model acts and it can…
We consider scenario in which our $(3+1)$-dim universe is actually a dense stack of multiple parallel $(2+1)$-dim branes. For this purpose, we generalize the DGP model to a multi-brane case. We solve for the propagation of the scalar field and gravity in this setup. At short distances (high momenta) along the branes interactions follow the $(2+1)$-dim laws, while at large distances (low momenta) interactions follow the usual $(3+1)$-dim laws. This feature is inherited from the original DGP model. In the direction perpendicular to the brane, we show that interactions become $(3+1)$-dim at low m…
We consider charged rotating black holes localized on a three-brane in the DGP model. Assuming a $Z_2$-symmetry across the brane and with a stationary and axisymmetric metric ansatz on the brane, a particular solution is obtained in the Kerr-Schild form. This solution belongs to the accelerated branch of the DGP model and has the characteristic of the Kerr-Newman-de Sitter type solution in general relativity. Using a modified version of Boyer-Lindquist coordinates we examine the structures of the horizon and ergosphere.
The self-accelerating branch of the Dvali-Gabadadze-Porrati (DGP) five-dimensional braneworld has provided a compelling model for the current cosmic acceleration. Recent observations, however, have not favored it so much. We discuss the solutions which contain a de Sitter 3-brane in the cascading DGP braneworld model, which is a kind of higher-dimensional generalizations of the DGP model,where a $p$-dimensional brane is placed on a $(p+1)$-dimensional one and the $p$-brane action contains the $(p+1)$-dimensional induced scalar curvature term. In the simplest six-dimensional model, we derive th…
We consider a DGP brane scenario where a scalar field is present on the brane through the introduction of a scalar potential, itself motivated by the notion of modified gravity. This theory predicts that the mass appearing in the gravitational potential is modified by the addition of the mass of the scalar field. The cosmological implications that such a scenario entails are examined and shown to be consistent with a universe expanding with power-law acceleration.
A DGP brane-world framework is picked out to study quark-hadron phase transition problem. The model also includes a bulk scalar field in agreement with string theory prediction. The work is performed utilizing two formalisms as: smooth crossover approach and first order approach, and the results are plotted for both branches of DGP model. General behavior of temperature is the same in these two approaches and it decrease by passing time and expanding Universe. Phase transition occurs at about micro-second after the big bang. The results show that transition time depends on brane tension value …
We find an exact solution on the brane for static black hole in the DGP model. In the appropriate limit we recover the 2 known solutions, the Schwarzschild and the Reissner-Nordstrom solutions with tidal charge. The solution has 2 branches, which correspond asymptotically to de-Sitter or flat Universe. Also we study the linear stability of the solutions. We find that the Regge-Wheeler and the Zerilli potential are positive. Finally the dipole perturbation is derived which corresponds to a linearization of a rotating black hole solution on the brane.
The braneworld model of Dvali, Gabadadze and Porrati (DGP) provides an intriguing modification of gravity at large distances and late times. By embedding a three-brane in an uncompactified extra dimension with separate Einstein-Hilbert terms for both brane and bulk, the DGP model allows for an accelerating universe at late times even in the absence of an explicit vacuum energy. We examine the evolution of cosmological perturbations on large scales in this theory. At late times, perturbations enter a DGP regime in which the effective value of Newton's constant increases as the background densit…
By studying a tachyon field on the DGP brane model, in order to embed the 4D standard Friedmann equation with a brane tachyon field in 5D bulk, the metric of the 5D spacetime is presented. Then, adopting the inverse square potential of tachyon field, we obtain an expanding universe with power-law on the brane and an exact 5D solution.
We consider charged black holes localized on a three-brane in the DGP model. With a spherically symmetric metric ansatz on the brane and assuming a Z_2-symmetry across the brane, we find two types of solutions which correspond to the so-called regular and accelerated branches in the DGP model. When the charge of the black hole vanishes, our solutions agree with the Schwarzschild solutions obtained by Gabadadze and Iglesias.
We study dynamics of equation of state parameter for a non-minimally coupled quintom dark energy component on the warped DGP brane. We investigate crossing of the cosmological constant line in this scenario. This crossing occurs in both DGP$^{\pm}$ branches of the model.
We consider a five dimensional DGP-brane scenario endowed with a non-minimally coupled scalar field within the context of Brans-Dicke theory. This theory predicts that the mass appearing in the gravitational potential is modified by the addition of the mass of the effective intrinsic curvature on the brane. We also derive the effective four dimensional field equations on a 3+1 dimensional brane where the fifth dimension is assumed to have an orbifold symmetry. Finally, we discuss the cosmological implications of this setup, predicting an accelerated expanding universe with a value of the Brans…
We consider a DGP inspired brane scenario where the action on the brane is augmented by a function of the Ricci scalar, ${\cal L}(R)$. The cosmological implications that such a scenario entails are examined for $R^{n}$ and shown to be consistent with a universe expanding with power-law acceleration. It is shown that two classes of solutions exist for the usual FRW metric and small Hubble radii. When the Hubble radius becomes larger, we either have a transition to a fully 5D regime or to a self-inflationary solution which produces a late accelerated expansion such that the radius becomes a func…
We give blueprints of the Schwinger-DeWitt technique for the covariant curvature expansion of quantum effective action for the DGP type models in curved spacetime.
We find an exact solution of Kerr-Newman-de Sitter type on the braneworld(4D) of the DGP model. When a constant 4D Ricci scalar is assumed, only zero(flat) and a positive(de-Sitter) values satisfy the Hamiltonian constraint equation coming from the extra dimension. With a Z_2-symmetry across the brane and a stationary and axisymmetric metric ansatz on the brane, we solve the constraint equation exactly in the Kerr-Schild form with de-Sitter background. In the de-Sitter background this Kerr-Schild solution is well behaved under Boyer-Lindquist transformation: the constraint equation is preserve…
A thin limit description of the 6D Cascading DGP model is derived, starting from a configuration where both the codimension-1 and the codimension-2 branes are thick. Postulating that the thicknesses of the two branes obey a hierarchic relation, the thin limit is executed in two steps. First the thin limit of the codimension-1 brane is executed, obtaining a system where a "ribbon" codimension-2 brane is embedded inside a thin codimension-1 brane with induced gravity, and then the thin limit of the ribbon brane is considered. By proposing a geometric ansatz on the limit configuration, the juncti…
We study the static, analytical solution of black holes in the warped DGP braneworld scenario. We show that the linearized field equations and matching conditions lead to solutions that are not compatible with Schwarzschild-(A)dS$_{(4)}$ solutions on the brane. This incompatibility is similar to vDVZ discontinuity in massive gravity theory. Following the standard procedure to remove this discontinuity, which firstly was proposed by Vainshtein, we keep some appropriate nonlinear terms in the field equations. This strategy has its origin in the fact that the spatial extrinsic curvature of the br…
We construct a warm inflation model with inflaton field non-minimally coupled to induced gravity on a warped DGP brane. We incorporate possible modification of the induced gravity on the brane in the spirit of $f(R)$-gravity. We study cosmological perturbations in this setup. In the case of two field inflation such as warm inflation, usually entropy perturbations are generated. While it is expected that in the case of one field inflation these perturbations to be removed, we show that even in the absence of the radiation field, entropy perturbations are generated in our setup due to non-minima…
We construct a DGP inspired braneworld scenario where a scalar field non-minimally coupled to the induced Ricci curvature is present on the brane. We show that this model allows for an embedding of the standard Friedmann cosmology in the sense that the cosmological evolution of the background metric on the brane can be described by the standard Friedmann equation. The relation between our framework and the dark-energy formalism is explored.
We investigate the cosmological consequences of a two brane system embedded in a higher dimensional background spacetime with a compactified extra dimension described with an action that include the intrinsic curvature for each brane. We find that the dynamics of each brane is related to the other by means of cosmological restrictions that involve the scale factors, the equation of state parameters and the Hubble parameters of the two branes. We analyze the evolution of the scale factor and the equation of state parameter for the hidden brane when in the visible brane is present a cosmological…
We examine brane induced gravity on codimension-1 branes, a.k.a DGP gravity, as a theory of five-dimensional gravity containing a certain class four-dimensional branes. From this perspective, the model suffers from a number of pathologies which went unnoticed before. By generalizing the 5D geometry from Minkowski to Schwarzschild, we find that when the bulk mass is large enough, the brane hits a pressure singularity at finite radius. Further, on the self-accelerating branch, the five-dimensional energy is unbounded from below, implying that the self-accelerating backgrounds are unstable. Even …
Warm inflationary universe models on a warped Dvali-Gabadadze-Porrati brane are studied. General conditions required for these models to be realizable are derived and discussed. By using an effective exponential potential we develop models for constant and variable dissipation coefficient ratio $r=\fracΓ{3 H}$. We use recent astronomical observations for constraining the parameters appearing in our models.
Using the data coming from the new 182 Gold type Ia supernova samples, the baryon acoustic oscillation measurement from the Sloan Digital Sky Survey and the H(z) data, we have performed a statistical joint analysis of the DGP brane-world model with a high curvature Gauss-Bonnet term in the bulk. Consistent parameters estimations show that the Gauss-Bonnet-Induced Gravity model is a viable candidate to explain the observed acceleration of our universe.
We construct exact solutions with the bubble of nothing in the Dvali-Gabadadze-Porrati braneworld model. The configuration with a single brane can be constructed, unlike in the Randall-Sundrum braneworld model. The geometry on the single brane looks like the Einstein-Rosen bridge. We also discuss the junction of multibranes. Surprisingly, even without any artificial matter fields on the branes such as three-dimensional tension of the codimension-two objects, two branes can be connected in certain configurations. We investigate solutions of multibranes too. The presence of solutions may indicat…
We study how the DGP (Dvali-Gabadadze-Porrati) brane affects particle dynamics in linearized approximation. We find that once the particle is removed from the brane it is repelled to the bulk. Assuming that the cutoff for gravitational interaction is $M_*\sim 1/ε$, we calculate the classical self energy of a particle as the function of its position. Since the particle wants to go to the region where its self energy is lower, it is repelled from the brane to the bulk where it gains its 5D self energy. Cases when mass of the particle $m<8π^2M_*$ and $m>8π^2M_*$ are qualitatively different, and i…
We revisit the 5D gravity model by Dvali, Gabadadze, and Porrati (DGP). Within their framework it was shown that even in 5D non-compact Minkowski space $(x^μ,z)$, the Newtonian gravity can emerge on a brane at short distances by introducing a brane-localized 4D Einstein-Hilbert term $δ(z)M_4^2\sqrt{|\bar{g}_4|}\bar{R}_4$ in the action. Based on this idea, we construct simple setups in which graviton standing waves can arise, and we introduce brane-localized $z$ derivative terms as a correction to $δ(z)M_4^2\sqrt{|\bar{g}_4|}\bar{R}_4$. We show that the gravity potential of brane matter becomes…
Large extra dimensions provide interesting extensions of our parameter space for gravitational theories. There exist now brane models which can perfectly reproduce standard four-dimensional Friedmann cosmology. These models are not motivated by observations, but they can be helpful in developing new approaches to the dimensionality problem in string theory. I describe the embedding of standard Friedmann cosmology in the DGP model, and in particular the realization of our current (dust+Lambda)-dominated universe in this model.
An impressed feature of inflation on warped Dvali-Gabadadze-Porrati (DGP) brane is that the inflationary phase exits spontaneously for a scalar inflaton field with exponential potential, which presents a graceful exit mechanism for the inflation. But its reheating mechanism leaves open. We investigate the curvaton reheating in inflation on warped DGP brane model. The reheating may occur in effctively 5 dimensional or 4 dimensional stage. We study the permitted parameter space of the curvaton field in detail. We demonstrate how the inflation model of the warped DGP brane is improved by the curv…
In the present paper, we present an extra dimensions inspired model that is built on the DGP brane-world scenario, then we take the dark energy component on the brane to be a Chaplygin gas. After that we consider a holographic model of Chaplygin gas in the framework of DGP cosmology. We show that the holographic Chaplygin gas can mimic a phantom fluid and cross the phantom divide in a DGP brane-world setup.
In this paper we first obtain Friedmann equations for the $(n-1)$-dimensional brane embedded in the $(n+1)$-dimensional bulk, with intrinsic curvature term of the brane included in the action (DGP model). Then, we show that one can always rewrite the Friedmann equations in the form of the first law of thermodynamics, $dE=TdS+WdV$, at apparent horizon on the brane, regardless of whether there is the intrinsic curvature term on the brane or a cosmological constant in the bulk. Using the first law, we extract the entropy expression of the apparent horizon on the brane. We also show that in the ca…
We study quasi-static perturbations in a cosmological background in the Dvali-Gabadadze-Porrati (DGP) braneworld model. We identify the Vainshtein radius at which the non-linear interactions of the brane bending mode become important in a cosmological background. The Vainshtein radius in the early universe is much smaller than the one in the Minkowski background, but in a self-accelerating universe it is the same as the Minkowski background. Our result shows that the perturbative approach is applicable beyond the Vainshtein radius for weak gravity by taking into account the second order effect…
We investigate how the laws of gravity change in the DGP model, if we add a second, parallel 3-brane, endowed with a localized gravitational curvature term. We calculate the gravitational potential energy between two static point sources localized on different branes. We discover a new length scale, which is equal to the geometric mean of the DGP cross-over scale and the separation of the two branes in the extra dimension. For distances, which are larger than this new length scale, we recover the original DGP result, but for smaller distances the gravitational potential is weaker. Furthermore,…
We construct a DGP inspired braneworld scenario where a scalar field non-minimally coupled to the induced Ricci curvature is present on the brane. First we investigate the status of gravitational potential with non-minimal coupling and observational constraints on this non-minimal model. Then we further deepen the idea of embedding of FRW cosmology in this non-minimal setup. Cosmological implications of this scenario are examined with details and the quintessence and late-time expansion of the universe within this framework are examined. Some observational constraints imposed on this non-minim…
We construct an inflation model with inflaton non-minimally coupled to gravity on a warped DGP brane. Using an exponential potential, we calculate scalar power spectrum, spectral index and the running of the spectral index. We show that for a suitable range of non-minimal coupling it is possible to exit the inflationary phase spontaneously and without any mechanism, even in the case that minimal inflation can not exit spontaneously. By a detailed analysis of parameter space, we study the constraints imposed on the non-minimal coupling from recent observational data.
We investigate the Dvali-Gabadadze-Porrati (DGP) model corrected by higher curvature brane terms. We show that these corrections have a dramatic impact on the spectrum of the model at the linearized level. Owing to the presence of higher derivatives in the field equations very massive ghost excitations with mass of order of Planck mass are generated in the ordinary branch of the model. These excitations describe an instability of Minkowski vacuum with time-scale of order of the Hubble time. At large distances these tachyonic excitations are expected to decouple from brane-localized matter. Our…
We construct a quintom dark energy model with two non-minimally coupled scalar fields, one quintessence and the other phantom field, confined on the warped DGP brane. We study some important issues such as phantom divide line crossing, existence of the bouncing solutions and the stability of the solutions in this framework. We show that this model accounts for crossing of the phantom divide line and realization of the bouncing solutions. This model allows for stability of the solutions in separate regions of the $ω$-$ω'$ phase-plane.
We propose a generalised induced gravity brane-world model where the brane action contains an arbitrary f(R) term, R being the scalar curvature of the brane. We show that the effect of the f(R)term on the dynamics of a homogeneous and isotropic brane is twofold: (i) an evolving induced gravity parameter and (ii) a shift on the energy density of the brane. This new shift term, which is absent on the Dvali, Gabadadze and Porrati (DGP) model, plays a crucial role to self-accelerate the generalised normal DGP branch of our model. We analyse as well the stability of de Sitter self-accelerating solu…
The braneworld model of Dvali-Gabadadze-Porrati (DGP) provides an interesting alternative to a positive cosmological constant by modifying gravity at large distances. We investigate the asymptotic behavior of homogeneous and anisotropic cosmologies on the DGP brane. It is shown that all Bianchi models except type IX isotropize, as in general relativity, if the so called $E_{μν}$ term satisfies some energy condition. Isotropization can proceed slower in DGP gravity than in general relativity.
Newton potential for DGP brane-world scenario is examined when the extra dimension is semi-infinite. The final form of the potential involves a self-adjoint extension parameter $α$, which plays a role of an additional mass (or distance) scale. The striking feature of Newton potential in this setup is that the potential behaves as seven-dimensional in long range when $α$ is nonzero. For small $α$ there is an intermediate range where the potential is five-dimensional. Five-dimensional Newton constant decreases with increase of $α$ from zero. In the short range the four-dimensional behavior is re…
We present a higher codimension generalization of the DGP scenario which, unlike previous attempts, is free of ghost instabilities. The 4D propagator is made regular by embedding our visible 3-brane within a 4-brane, each with their own induced gravity terms, in a flat 6D bulk. The model is ghost-free if the tension on the 3-brane is larger than a certain critical value, while the induced metric remains flat. The gravitational force law `cascades' from a 6D behavior at the largest distances followed by a 5D and finally a 4D regime at the shortest scales.
Braneworld models with induced gravity have the potential to replace dark energy as the explanation for the current accelerating expansion of the Universe. The original model of Dvali, Gabadadze and Porrati (DGP) demonstrated the existence of a ``self--accelerating'' branch of background solutions, but suffered from the presence of ghosts. We present a new large class of braneworld models which generalize the DGP model. Our models have negative curvature in the bulk, allow a second brane, and have general brane tensions and localized curvature terms. We exhibit three different kinds of ghosts,…
In this paper, the Dvali-Gabadadze-Porrati (DGP) brane model is confronted by current cosmic observational data sets from geometrical and dynamical perspectives. On the geometrical side, the recent released Union2 $557$ of type Ia supernovae (SN Ia), the baryon acoustic oscillation (BAO) from Sloan Digital Sky Survey and the Two Degree Galaxy Redshift Survey (transverse and radial to line-of-sight data points), the cosmic microwave background (CMB) measurement given by the seven-year Wilkinson Microwave Anisotropy Probe observations (shift parameters $R$, $l_a(z_\ast)$ and redshift at the last…
The braneworld model of Dvali-Gabadadze-Porrati realizes the self-accelerating universe. However, it is known that this cosmological solution contains a spin-2 ghost. We study the possibility of avoiding the appearance of the ghost by slightly modifying the model, introducing the second brane. First we consider a simple model without stabilization of the separation of the brane. By changing the separation between the branes, we find we can erase the spin-2 ghost. However, this can be done only at the expense of the appearance of a spin-0 ghost instead. We discuss why these two different types …
In the decoupling limit of DGP, Pi describes the brane-bending degree of freedom. It obeys second order equations of motion, yet it is governed by a higher derivative Lagrangian. We show that, analogously to the Einstein-Hilbert action for GR, the Pi-Lagrangian requires Gibbons-Hawking-York type boundary terms to render the variational principle well-posed. These terms are important if there are other boundaries present besides the DGP brane, such as in higher dimensional cascading DGP models. We derive the necessary boundary terms in two ways. First, we derive them directly from the brane-loc…
We address the vDVZ discontinuity of the 5D DGP model which consists of a 3-brane residing in a flat, infinite-volume bulk. Following a suggestion by Gabadadze [hep-th/0403161], we implement a constrained perturbative expansion parametrized by brane gauge parameters. We explore the parameter space and show that the DGP solution exhibiting the vDVZ discontinuity corresponds to a set of measure zero.
In the standard picture of cosmology it is predicted that a phase transition, associated with chiral symmetry breaking after the electroweak transition, has occurred at approximately 10 μseconds after the Big Bang to convert a plasma of free quarks and gluons into hadrons. We consider the quark-hadron phase transition in a DGP brane world scenario within an effective model of QCD. We study the evolution of the physical quantities useful for the study of the early universe, namely, the energy density, temperature and the scale factor before, during, and after the phase transition. Also, due to …
We study the behaviour of weak gravitational fields in the 6D Cascading DGP model using a bulk-based approach. To deal with the ambiguity in the thin limit of branes of codimension higher than one, we consider a specific regularization of the internal structure of the branes where the 5D brane can be considered thin with respect to the 4D one. We consider the solutions corresponding to pure tension sources on the 4D brane, and study perturbations at first order around these background solutions. We adopt a 4D scalar-vector-tensor decomposition, and focus on the scalar sector of perturbations. …
We consider the asymmetric branes model of modified gravity, which can produce late time acceleration of the universe and compare the cosmology of this model to the standard $Λ$CDM model and to the DGP braneworld model. We show how the asymmetric cosmology at relevant physical scales can be regarded as a one-parameter extension of the DGP model, and investigate the effect of this additional parameter on the expansion history of the universe.
We investigate the validity of the generalized second law of thermodynamics on the $(n-1)$-dimensional brane embedded in the $(n+1)$-dimensional bulk. We examine the evolution of the apparent horizon entropy extracted through relation between gravitational equation and the first law of thermodynamics together with the matter field entropy inside the apparent horizon. We find that the apparent horizon entropy extracted through connection between gravity and the first law of thermodynamics satisfies the generalized second law of thermodynamics. This result holds regardless of whether there is th…
The Dvali-Gabadadze-Porrati brane-world model provides a possible approach to address the late-time cosmic acceleration. However, it has subsequently been pointed out that a ghost instability will arise on the self-accelerating branch. Here, we carefully investigate whether this ghost problem could be possibly cured by introducing the Gauss-Bonnet term in the five-dimensional bulk action, a natural generalization to the Dvali-Gabadadze-Porrati model. Our analysis is carried out for a background where a de Sitter brane is embedded in an anti-de Sitter bulk. Our result shows that the ghost excit…
We develop the Schwinger-DeWitt technique for the covariant curvature expansion of the quantum effective action for brane induced gravity models in curved spacetime. This expansion has a part nonanalytic in DGP type scale parameter, leading to the cutoff scale which is given by the geometric average of the mass of the quantum field in the bulk and DGP scale. This cutoff is much higher than the analogous strong coupling scale of the DGP model treated by weak field expansion in the tree-level approximation. The lowest orders of this curvature expansion are calculated for the case of the scalar f…
We develop a scaling ansatz for the master equation in Dvali, Gabadadze, Porrati cosmologies, which allows us to solve the equations of motion for perturbations off the brane during periods when the on-brane evolution is scale-free. This allows us to understand the behavior of the gravitational potentials outside the horizon at high redshifts and close to the horizon today. We confirm that the results of Koyama and Maartens are valid at scales relevant for observations such as galaxy-ISW correlation. At larger scales, there is an additional suppression of the potential which reduces the growth…
The Dvali-Gabadadze-Porrati model introduces a parameter, the cross-over scale $r_c$, setting the scale where higher dimensional effects are important. In order to agree with observations and to explain the current acceleration of the Universe, $r_c$ must be of the order of the present Hubble radius. We discuss a mechanism to generate a large $r_c$, assuming that it is determined by a dynamical field and exploiting the quantum effects of the graviton. For simplicity, we consider a scalar field $Ψ$ with a kinetic term on the brane instead of the full metric perturbations. We compute the Green f…
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 redshifts. We reinterpret the effective phantom nature of the dark energy as arising from dynamical-screening of the brane cosmological constant in DGP. This unusual variety of expansion history is thus…
The DGP-model with additional terms in the action is considered. These terms have a special form and include auxiliary scalar fields without kinetic terms, which are non-minimally coupled to gravity. The use of these fields allows one to exclude the mode, which corresponds to the strong coupling effect, from the theory. Effective four-dimensional theory on the brane appears to be the same, as in the original DGP-model.
We derive the modified Friedmann equations for a generalization of the Dvali-Gabadadze-Porrati (DGP) model in which the brane has one additional compact dimension. The main new feature is the emission of gravitational waves into the bulk. We study two classes of solutions: First, if the compact dimension is stabilized, the waves vanish and one exactly recovers DGP cosmology. However, a stabilization by means of physical matter is not possible for a tension-dominated brane, thus implying a late time modification of 4D cosmology different from DGP. Second, for a freely expanding compact directio…
