排序方式: 共有18条查询结果,搜索用时 156 毫秒
1.
A cosmological scenario with two branes (A and B) moving in a 5-dimensional bulk is considered. As in the case of ecpyrotic and born-again braneworld models it is possible that the branes collide. The energy-momentum tensor is taken to describe a perfect barotropic fluid on the A-brane and a phenomenological time-dependent cosmological constant on the B-brane. The A-brane is identified with our Universe and its cosmological evolution in the approximation of a homogeneous and isotropic brane is analysed. The dynamics of the radion (a scalar field on the brane) contains information about the proper distance between the branes. It is demonstrated that the deSitter type solutions are obtained for late time evolution of the braneworld and accelerative behaviour is anticipated at the present time. 相似文献
2.
We derive the low energy effective action for the dilatonic braneworld. In the case of the single-brane model, we find the effective theory is described by the Einstein-scalar theory coupled to the dark radiation. Remarkably, the dark radiation is not conserved in general due to a coupling to the bulk scalar field. The effective action incorporating Kaluza-Klein (KK) corrections is obtained and the role of the AdS/CFT correspondence in the dilatonic braneworld is revealed. In particular, it is shown that CFT matter would not be confined to the braneworld in the presence of the bulk scalar field. The relation between our analysis and the geometrical projection method is also clarified. In the case of the two-brane model, the effective theory reduces to a scalar-tensor theory with a non-trivial coupling between the radion and the bulk scalar field. 相似文献
3.
Benedict?M.?N.?CarterEmail author Alex?B.?Nielsen 《General Relativity and Gravitation》2005,37(9):1629-1634
The static potential for a massless scalar field shares the essential features of the scalar gravitational mode in a tensorial
perturbation analysis about the background solution. Using the fluxbrane construction of [8] we calculate the lowest order
of the static potential of a massless scalar field on a thin brane using series solutions to the scalar field's Klein Gordon
equation and we find that it has the same form as Newton's Law of Gravity. We claim our method will in general provide a quick
and useful check that one may use to see if their model will recover Newton's Law to lowest order on the brane. 相似文献
4.
Bulk antisymmetric tensor fields of different ranks have been studied in the context of a generalized Randall–Sundrum model with a non-vanishing induced cosmological constant on the visible brane. It is shown that instead of the usual exponential suppression of the couplings of the zero modes of these bulk fields with the brane fermions in the original Randall–Sundrum model, here the couplings are proportional to the brane cosmological constant. Thus in an era of large cosmological constant these fields have significant role in physical phenomena because of their enhanced couplings with the visible brane fermions. 相似文献
5.
It has been shown recently that the normal branch of a DGP braneworld scenario self-accelerates if the induced gravity on the brane is modified in the spirit of f(R) modified gravity. Within this viewpoint, we investigate cosmological viability of the Hu-Sawicki type modified induced gravity. Firstly, we present a dynamical system analysis of a general f(R)-DGP model. We show that in the phase space of the model, there exist three standard critical points; one of which is a de Sitter point corresponding to accelerating phase of the universe expansion. The stability of this point depends on the effective equation of state parameter of the curvature fluid. If we consider the curvature fluid to be a canonical scalar field in the equivalent scalar-tensor theory, the mentioned de Sitter phase is unstable, otherwise it is an attractor, stable phase. We show that the effective equation of state parameter of the model realizes an effective phantom-like behavior. A cosmographic analysis shows that this model, which admits a stable de Sitter phase in its expansion history, is a cosmologically viable scenario. 相似文献
6.
Everton M.C. Abreu 《Physics letters. [Part B]》2011,704(4):322-325
Rubakov and Shaposhnikov (RSH), in a seminal paper, discussed the possibility that particles are confined in a potential well. This is considered as the first mention to the today?s idea that we live in a brane, i.e., the braneworld concept. In this work we show precisely that the proposed RSH model has a gauge invariant equivalent action and we discuss it in the light of braneworld structure. We analyzed the intrinsic features of both models trying to disclose new properties within RSH braneworld theory. 相似文献
7.
In the framework of the braneworld models, rotating black holes can be described by the Kerr metric with a tidal charge representing
the influence of the non-local gravitational (tidal) effects of the bulk space Weyl tensor onto the black hole spacetime.
We study the influence of the tidal charge onto profiled spectral lines generated by radiating tori orbiting in vicinity of
a rotating black hole. We show that with lowering the negative tidal charge of the black hole, the profiled line becomes to
be flatter and wider keeping their standard character with flux stronger at the blue edge of the profiled line. The extension
of the line grows with radius falling and inclination angle growing. With growing inclination angle a small hump appears in
the profiled lines due to the strong lensing effect of photons coming from regions behind the black hole. For positive tidal
charge (b > 0) and high inclination angles two small humps appear in the profiled lines close to the red and blue edge of the lines
due to the strong lensing effect. We can conclude that for all values of b, the strongest effect on the profiled lines shape (extension) is caused by the changes of the inclination angle. 相似文献
8.
Edmundo M. Monte 《International Journal of Theoretical Physics》2009,48(2):409-413
The braneworlds models were inspired partly by Kaluza-Klein’s theory, where both the gravitational and the gauge fields are
obtained from the geometry of a higher dimensional space. The positive aspects of these models consist in perspectives of
modifications it could bring in to particle physics, such as: unification in a TeV scale, quantum gravity in this scale and
deviation of Newton’s law for small distances. One of the principles of these models is to suppose that all space-times can
be embedded in a bulk of higher dimension. The main result in these notes is a theorem showing a mathematical inconsistency
of the Randall-Sundrum braneworld model, namely that the Schwarzschild space-time cannot be embedded locally and isometrically
in a five dimensional bulk with constant curvature (for example AdS-5). From the point of view of semi-Riemannian geometry
this last result represents a serious restriction to the Randall-Sundrum’s braneworld model. 相似文献
9.
Homogeneous cosmology in the braneworld can be studied without solving bulk equations of motion explicitly. The reason is
simply because the symmetry of the spacetime restricts possible corrections in the 4-dimensional effective equations of motion.
It would be great if we could analyze cosmological perturbations without solving the bulk. For this purpose, we combine the
geometrical approach and the low energy gradient expansion method to derive the 4-dimensional effective action. Given our
effective action, the standard procedure to obtain the cosmological perturbation theory can be utilized and the temperature
anisotropy of the cosmic background radiation can be computed without solving the bulk equations of motion explicitly. 相似文献
10.
We consider a Vaidya-type radiating spacetime in Einstein gravity with the Gauss-Bonnet combination of quadratic curvature
terms. Simply generalizing the known static black hole solutions in Einstein-Gauss-Bonnet gravity, we present an exact solution
in arbitrary dimensions with the energy-momentum tensor given by a null fluid form. As an application, we derive an evolution
equation for the “dark radiation” in the Gauss-Bonnet braneworld. 相似文献