共查询到20条相似文献,搜索用时 468 毫秒
1.
Subenoy Chakraborty Soma Nath Tanwi Bandyopadhyay 《International Journal of Theoretical Physics》2009,48(1):29-35
In this letter, we have obtained static, spherically symmetric solutions of the effective vacuum Einstein field equations
on a brane embedded in a five dimensional space time. The effective stress tensor is induced by the interaction with the bulk
gravitational field and is given by the electric part of the five dimensional Weyl tensor. Due to traceless nature of this
non-local effect of the bulk, any solution of (4)
R=0 is a possible solution of the vacuum brane. We have derived a class of solutions, which corresponds to wormhole solution.
Physical properties and characteristics of the wormhole are studied. 相似文献
2.
3.
K. Saaidi S. W. Rabiei A. Aghamohammadi 《International Journal of Theoretical Physics》2011,50(8):2514-2519
We study spherically symmetric static empty space solutions in R+ε/R model of f(R) gravity. We show that the Schwarzschild metric is an exact solution of the resulted field equations and consequently there
are general solutions which are perturbed Schwarzschild metric and viable for solar system. Our results for large scale contains
a logarithmic term with a coefficient producing a repulsive gravity force which is in agreement with the positive acceleration
of the universe. 相似文献
4.
We study in a self-consistent way the impact of the emission of bulk gravitons on the (homogeneous) cosmology of a three-brane embedded in a five-dimensional spacetime. In the low energy regime, we recover the well known result that the bulk affects the Friedmann equation only via a radiationlike term C/a(4), called dark or Weyl radiation. In the high energy regime, we find that the Weyl parameter C is no longer constant but grows rapidly. Consequently, C today is determined by the past history of the brane universe and depends on the number of relativistic degrees of freedom at the high/low energy transition. 相似文献
5.
In this paper, we examine the possibility of static, spherically symmetric gravitational geons on a 3 dimensional brane embedded
in a 4+1 dimensional space-time. We choose a specific g
tt
for the brane-world space-time metric. We then calculate g
rr
analytically in the weak field limit and numerically for stronger fields. We show that the induced field equations on the
brane do admit gravitational geon solutions. 相似文献
6.
The modified gravitational equations to describe a four-dimensional braneworld in the case with the Lorentz invariant violation
in a bulk spacetime is presented. It contains a trace part of the brane energy-momentum tensor and the coefficients of all
terms describe the Lorentz violation effects from the bulk spacetime. As an application, we apply this formalism to study
cosmology. In respect to standard effective Friedmann equations on the brane, Lorentz invariance violation in the bulk causes
a modification of this equations that can lead to significant physical consequences. In particular, the effective Friedmann
equation on the brane explicitly depends on the equation of state of the brane matter and the Lorentz violating parameters.
We show that the components of five-dimensional Weyl curvature are related to the matter on brane even at low energies. We
also find that the constraints on the theory parameters are depend on the equation of state of the energy components of the
brane matter. Finally, the stability of the model depend on the specific choices of initial conditions and the parameters
β
i
. 相似文献
7.
We obtain exact cosmological solutions of a higher derivative theory described by the Lagrangian L=R+2αR
2 in the presence of interacting scalar field. The interacting scalar field potential required for a known evolution of the
FRW universe in the framework of the theory is obtained using a technique different from the usual approach to solve the Einstein
field equations. We follow here a technique to determine potential similar to that used by Ellis and Madsen in Einstein gravity.
Some new and interesting potentials are noted in the presence of R
2 term in the Einstein action for the known behaviours of the universe. These potentials in general do not obey the slow rollover
approximation. 相似文献
8.
T. R. P. Caramês E. R. Bezerra de Mello 《The European Physical Journal C - Particles and Fields》2009,64(1):113-121
In this paper we investigate spherically symmetric vacuum solutions of f(R) gravity in a higher-dimensional spacetime. With this objective we construct a system of non-linear differential equations
whose solutions depend on the explicit form assumed for the function
F(R)=\fracdf(R)dRF(R)=\frac{df(R)}{dR}
. We explicit show that for specific classes of this function exact solutions from the field equations are obtained; also
we find approximated results for the metric tensor for more general cases admitting F(R) close to the unity. 相似文献
9.
Dan N. Vollick 《General Relativity and Gravitation》2002,34(1):1-7
It has recently been proposed that our universe is a three-brane embedded in a higher dimensional spacetime. Here I show that black holes on the brane, black strings intersecting the brane, and gravitational waves propagating in the bulk induce an effective energy-momentum tensor on the brane that contains negative energy densities. 相似文献
10.
B. Mieck 《Fortschritte der Physik》2005,53(9):1072-1082
The Skyrme model is generalized for a noncommutative spacetime with the Weyl‐operators of SU(2) matrices and the corresponding star‐product. The unitary condition and the topological current can be extended to star‐exponential matrices. The Wess‐Zumino term which breaks unphysical symmetries of the Skyrme action is gauged with the U*(1) group to allow for electromagnetic processes in a noncommutative spacetime. Apart from corrections to the anomalous decay γ→π0π+π– in commuting spacetime, the additional anomalous process γ→π0π0π0 is found in the U*(1) gauged Wess‐Zumino action for a noncommutative spacetime. 相似文献
11.
Considering an inhomogeneous brane embedded in a five dimensional constant curvature bulk, we find the non-static and spherically symmetric exact solutions of the Einstein equations on the brane. With different choices of the parameters, one interesting case/solution is studied. We show that an inhomogeneous brane model can explain the accelerated expansion of the universe at large distance scales and also the galaxy rotation curves of spiral galaxies without assuming the existence of dark matter or new modified theories at the galactic scales. 相似文献
12.
Based on the group theory powerful techniques, as a rigorous tool for treating fields on S
3 × R spacetime, which is the manifold of SU(2), we put the supersymmetric Wess–Zumino model on the S
3 × R background. After deriving the system of Klein–Gordon–Dirac-type equations, for the scalar and Majorana fields, we get in the corresponding current, besides the supercurrent, an additional term due to the coupling of spin to gravity. Finally, considerations on the solutions of the fields equations are made, pointing out significant differences from the Minkowskian case. 相似文献
13.
Samad Khakshournia 《General Relativity and Gravitation》2008,40(8):1791-1796
Within our thick brane approach previously used to obtain the cosmological evolution equations on a thick brane embedded in
a five-dimensional Schwarzschild Anti-de Sitter spacetime it is explicitly shown that the consistency of these equations with
the energy conservation equation requires that, in general, the thickness of the brane evolves in time. This varying brane
thickness entails the possibility that both Newton’s gravitational constant G and the effective cosmological constant Λ4 are time dependent. 相似文献
14.
Rommel Guerrero R. Omar Rodriguez Rafael Torrealba R. Ortiz 《General Relativity and Gravitation》2006,38(5):845-855
A new method to obtain thick domain wall solutions to the coupled Einstein scalar field system is presented. The procedure allows the construction of irregular walls from well known ones, such that the spacetime associated to them are physically different. As consequence of the approach, we obtain two irregular geometries corresponding to thick domain walls with dS expansion and topological double kink embedded in AdS spacetime. In particular, the double brane can be derived from a fake superpotential. 相似文献
15.
G. S. Khadekar Gopal L. Kondawar Cenap Ozel 《International Journal of Theoretical Physics》2008,47(7):1844-1852
The field equations with variable cosmological and gravitational constants are consider in the presence of perfect fluid for
Kaluza-Klein type cosmological model. The exact solutions of the field equations are obtained by using the gamma law equation
of state p=(γ−1)ρ in which the parameter γ depends on scale factor R. The functional form of γ(R) is used to analyze a wide range of cosmological solution at early universe for two phases in cosmic history: inflationary phase and radiation dominated phase. The corresponding physical interpretation of cosmological solution are also discussed in the framework of higher dimensional
space time. 相似文献
16.
S. K. Srivastava 《International Journal of Theoretical Physics》2008,47(7):1966-1978
Using modified gravity with non-linear terms of curvature, R
2 and R
(2+r) (with r being a positive real number and R being the scalar curvature), cosmological scenario, beginning at the Planck scale, is obtained. Here a unified picture of
cosmology is obtained from f(R)-gravity. In this scenario, universe begins with power-law inflation followed by deceleration and acceleration in the late universe
as well as possible collapse of the universe in future. It is different from f(R)-dark energy models with non-linear curvature terms assumed as dark energy. Here, dark energy terms are induced by linear as well as non-linear
terms of curvature in Friedmann equation being derived from modified gravity. It is also interesting to see that, in this
model, dark radiation and dark matter terms emerge spontaneously from the gravitational sector. It is found that dark energy,
obtained here, behaves as quintessence in the early universe and phantom in the late universe. Moreover, analogous to brane-tension
in brane-gravity inspired Friedmann equation, a tension term λ arises here being called as cosmic tension, It is found that, in the late universe, Friedmann equation (obtained here) contains
a term −ρ
2/2λ (ρ being the phantom energy density) analogous to a similar term in Friedmann equation with loop quantum effects, if λ>0 and brane-gravity correction when λ<0. 相似文献
17.
We investigate shear-free, perfect fluid solutions of Einstein's field equations in which the perfect fluid satisfies a barotropic equation of state p = p(w) such that w + p 0. We find that if the electric part of the Weyl tensor (with respect to the fluid flow) vanishes and the spacetime is not conformally flat then the fluid volume expansion is zero but the vorticity is necessarily nonzero. In addition, we show that if p = –w/3 then necessarily either the fluid expansion is zero or the fluid vorticity is zero. 相似文献
18.
19.
Lu-Xin Liu 《Physics of Atomic Nuclei》2011,74(12):1684-1689
In this paper a Weyl scale-invariant p = 3-brane scenario is introduced, with the brane embedded in a higher-dimensional bulk space with N = 1, 5D Super-Weyl symmetry. Its action, which describes its long wave oscillation modes into the ambient superspace and
breaks the target symmetry down to the lower dimensional Weyl W(1, 3) symmetry, is constructed by the approach of coset method. 相似文献
20.
K. A. Bronnikov S. B. Fadeev A. V. Michtchenko 《General Relativity and Gravitation》2004,36(7):1527-1535
For a static, spherically symmetric brane in the framework of the RS2 concept, we study the conditions under which the 4D tensor E
v, arising from the 5D Weyl tensor, vanishes on the brane. Gravity on the brane is then decoupled from the bulk geometry, it is the so-called minimally coupled brane world (MCBW). Assuming E
v =0 in the whole bulk, we try to solve the 5D Einstein equations G
AB
+ 5gAB
=0 and obtain an overdetermined set of equations for functions of the radial coordinate. Some special solutions are found, among which are the well-known black string solution with the Schwarzschild metric on the brane and its generalizations with Schwarzschild–(A)dS on-brane metrics. It is concluded that a MCBW can be embedded, in general, in a bulk where Ev is not identically zero but only vanishes on the brane. We also present some previous results on the general properties of scalar fields on the brane and give an example of a wormhole supported by a scalar field in a MCBW. 相似文献