共查询到20条相似文献,搜索用时 328 毫秒
1.
M. Farasat Shamir 《International Journal of Theoretical Physics》2011,50(3):637-643
The main purpose of this paper is to study the exact solution of Bianchi type III spacetime in the context of metric f(R) gravity. The field equations are solved by taking expansion scalar θ proportional to shear scalar σ which gives C=A
n
, where A and C are the metric coefficients. The physical behavior of the solution has been discussed using some physical quantities. Also,
the function of the Ricci scalar is evaluated. 相似文献
2.
Xiong-Wei Liu Shu-Zheng Yang Shi-Wu Chen Wen-Fu Wang 《International Journal of Theoretical Physics》2009,48(5):1478-1484
We find a new exact inflationary solution to non-minimally coupled scalar field from a specific H(φ). The inflation is driven by the evolution of the scalar field with a new inflation potential. The spectral index of the
scalar density fluctuations n
s
is consistent with the result of WMAP3 for the power-law flat ΛCDM model. Our solution relaxes the constraint to the quartic
coupling constant, e.g. when ξ=103, λ≤8.9×10−11. 相似文献
3.
S. Habib Mazharimousavi M. Halilsoy Z. Amirabi 《General Relativity and Gravitation》2010,42(2):261-280
We find large classes of non-asymptotically flat Einstein–Yang–Mills–Dilaton and Einstein–Yang–Mills–Born–Infeld–Dilaton black
holes in N-dimensional spherically symmetric spacetime expressed in terms of the quasilocal mass. Extension of the dilatonic
YM solution to N-dimensions has been possible by employing the generalized Wu-Yang ansatz. Another metric ansatz, which aided
in finding exact solutions is the functional dependence of the radius function on the dilaton field. These classes of black
holes are stable against linear radial perturbations. In the limit of vanishing dilaton we obtain Bertotti–Robinson type metrics
with the topology of AdS
2×S
N–2. Since connection can be established between dilaton and a scalar field of Brans–Dicke type we obtain black hole solutions
also in the Brans–Dicke–Yang–Mills theory as well. 相似文献
4.
K S Virbhadra 《Pramana》1995,44(4):317-322
A nonstatic and circularly symmetric exact solution of the Einstein equations (with a cosmological constant Λ and null fluid)
in 2 + 1 dimensions is given. This is a nonstatic generalization of the uncharged spinless BTZ metric. For Λ = 0, the spacetime
is though not flat, the Kretschmann invariant vanishes. The energy, momentum, and power output for this metric are obtained.
Further a static and circularly symmetric exact solution of the Einsteinmassless scalar equations is given, which has a curvature
singularity atr = 0 and the scalar field diverges atr = 0 as well as at infinity. 相似文献
5.
A spinor field interacting with a zero-mass neutral scalar field is considered for the case of the simplest type of direct
interaction, where the interaction Lagrangian has the formL
int
=1/2 ϕαϕ,α
F(S) whereF(S) is an arbitrary function of the spinor field invariantS=ψψ. Exact solutions of the corresponding systems of equations that take into account the natural gravitational field in a
plane-symmetric metric are obtained. It is proved that the initial system of equations has regular localized soliton-type
solutions only if the energy density of the zero-mass scalar field is negative as it “disengages” from interaction with the
spinor field. In two-dimensional space-time the system of field equations we are studying describes the configuration of fields
with constant energy densityT
00
, i.e., no soliton-like solutions exist in this case.
Russian People’s Friendship University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 69–75,
July, 1998. 相似文献
6.
V. I. Ritus 《Journal of Experimental and Theoretical Physics》2006,102(4):582-602
The symmetry manifests itself in exact relations between the Bogoliubov coefficients for processes induced by an accelerated
point mirror in 1 + 1 dimensional space and the current (charge) densities for the processes caused by an accelerated point
charge in 3 + 1 dimensional space. The spectra of pairs of Bose (Fermi) massless quanta emitted by the mirror coincide with
the spectra of photons (scalar quanta) emitted by the electric (scalar) charge up to the factor e
2/ħc. The integral relation between the propagator of a pair of oppositely directed massless particles in 1 + 1 dimensional space
and the propagator of a single particle in 3 + 1 dimensional space leads to the equality of the vacuum-vacuum amplitudes for
the charge and the mirror if the mean number of created particles is small and the charge e = √ħc. Due to the symmetry, the mass shifts of electric and scalar charges (the sources of Bose fields with spin 1 and 0 in 3 +
1 dimensional space) for the trajectories with a subluminal relative velocity β12 of the ends and the maximum proper acceleration w
0 are expressed in terms of the heat capacity (or energy) spectral densities of Bose and Fermi gases of massless particles
with the temperature w
0/2π in 1 + 1 dimensional space. Thus, the acceleration excites 1-dimensional oscillation in the proper field of a charge,
and the energy of oscillation is partly deexcited in the form of real quanta and partly remains in the field. As a result,
the mass shift of an accelerated electric charge is nonzero and negative, while that of a scalar charge is zero. The symmetry
is extended to the mirror and charge interactions with the fields carrying spacelike momenta and defining the Bogoliubov coefficients
αB,F. The traces trαB,F, which describe the vector and scalar interactions of the accelerated mirror with a uniformly moving detector, were found
in analytic form for two mirror trajectories with subluminal velocities of the ends. The symmetry predicts one and the same
value e
0
= √ħc for the electric and scalar charges in 3 + 1 dimensional space. Arguments are adduced in favor of the conclusion that this
value and the corresponding value α0 = 1/4π of the fine structure constant are the bare, nonrenormalized values.
The text was submitted by the author in English. 相似文献
7.
Eloy Ayón-Beato Cristián Martínez Jorge Zanelli 《General Relativity and Gravitation》2006,38(1):145-152
A nontrivial scalar field configuration of vanishing energy-momentum is reported. These matter configurations have no influence
on the metric and therefore they are not be “detected" gravitationally. This phenomenon occurs for a time–dependent nonminimally
coupled and self-interacting scalar field on the 2+1 (BTZ) black hole geometry. We conclude that such stealth configurations
exist for the static 2+1 black hole for any value of the nonminimal coupling parameter ζ≠0 with a fixed self-interaction potential
U
ζ(Φ). For the range 0 < ζ≤1/2 potentials are bounded from below and for the range 0 < ζ < 1/4 the stealth field falls into
the black hole and is swallowed by it at an exponential rate, without any consequence for the black hole. 相似文献
8.
J. Socorro Luis O. Pimentel C. Ortiz M. Aguero 《International Journal of Theoretical Physics》2009,48(12):3567-3585
Using the ADM formalism in the minisuperspace, we obtain the commutative and noncommutative exact classical solutions and
exact wave function to the Wheeler-DeWitt equation with an arbitrary factor ordering, for the anisotropic Bianchi type I cosmological
model, coupled to a scalar field, cosmological term and barotropic perfect fluid. We introduce noncommutative scale factors,
considering that all minisuperspace variables q
i
do not commute, so the symplectic structure was modified. In the classical regime, it is shown that the anisotropic parameter
β
±nc
and the field φ, for some value in the λ
eff cosmological term and noncommutative θ parameter, present a dynamical isotropization up to a critical cosmic time t
c
; after this time, the effects of isotropization in the noncommutative minisuperspace seems to disappear. In the quantum regimen,
the probability density presents a new structure that corresponds to the value of the noncommutativity parameter. 相似文献
9.
The Bethe-Salpeter formalism is used to incorporate the valence Regge behavior into the total DIS amplitude. For a special
case of scalar quarks with massless scalar exchange, the model is solved both analytically and numerically and exact scaling
is found for the valence quark contribution F
2(x) ∼ (1/x)
l(0)−1 which mimicks the ρ-trajectory term. The solution solves a long-standing problem by showing that the coefficient in the Regge
pole expansion is indeed fine-tuned to give the expected scaling. The method allows for generalization to the region of nonzero
momentum transfer and calculation of the DVCS amplitude.
The text was submitted by the authors in English. 相似文献
10.
Motivated by Kaluza-Klein theory and modern string theories, the class of exact solutions yielding product manifolds M
2 × S
2 in general relativity is investigated. The compact submanifold homeomorphic to S
2 is chosen to be a very small sphere. Choosing an anisotropic fluid as the particular physical model, it is proved that very large mass density and tension provide the mechanism of compactification. In case the transverse pressure is chosen to be zero, the corresponding spacetime is homeomorphic to 2 × S
2, and thus provides a tractable non-flat metric. In this simple metric, the geodesic equations are completely solved, yielding motions of massive test particles. Next, the corresponding wave mechanics (given by the Klein-Gordon equation) is explored in the same curved background. A general class of exact solutions is obtained. Four conserved quantities are explicitly computed. The scalar particles exhibit a discrete mass spectrum. 相似文献
11.
Satoshi Ikeda 《Annalen der Physik》1987,499(8):558-562
Some structural considerations are made on the Finslerian gravitational field: A Finslerian metrical structure such as gλχ(x, y) = γλχ(x) + hλχ(x, y) is proposed, where γλχ denotes the Riemann metric of Einstein's gravitational field, while hλχ the Finsler metric induced by the Riemann metric hij(y) of the internal field; The intrinsic behaviour of the internal variable y, which is expressed as ?i = K(x, y) yj in the internal field, is grasped by the Finslerian parallelism δyi (=0), which is reflected in the spatial structure of the external gravitational field by the mapping relation δyχ = e(x) δyi. The whole metrical Finsler connection D for gλχ(i.e., Dgλχ = 0) is determined by taking account of the intrinsic behaviour δyχ. 相似文献
12.
Fan Zhao 《International Journal of Theoretical Physics》2011,50(11):3509-3514
Taking WKB approximation to solve the scalar field equation in the Schwarzschild black hole spacetime, we can get the classical
momenta. Substituting the classical momenta into state density equation corrected by the modified dispersion relation, we
will obtain the number of quantum states with energy less than ω. Then, it is used to calculate the statistical-mechanical entropy of the scalar field in the Schwarzschild black hole spacetime.
By taking exact method, we obtained the leader term of entropy which is proportional to the event horizon area and correction
terms take the forms of ln A, A
−1ln A, A
−1 and so on. 相似文献
13.
Defining a spin connection is necessary for formulating Dirac's bispinor equation in a curved space-time. Hestenes has shown
that a bispinor field is equivalent to an orthonormal tetrad of vector fields together with a complex scalar field. In this
paper, we show that using Hestenes' tetrad for the spin connection in a Riemannian space-time leads to a Yang-Mills formulation
of the Dirac Lagrangian in which the bispinor field Ψ is mapped to a set of SL(2,R)× U(1) gauge potentials FαK and a complex scalar field ρ. This result was previously proved for a Minkowski space-time using Fierz identities. As an
application we derive several different non-Riemannian spin connections found in the literature directly from an arbitrary
linear connection acting on the tensor fields (FαK, ρ). We also derive spin connections for which Dirac's bispinor equation is form invariant. Previous work has not considered
form invariance of the Dirac equation as a criterion for defining a general spin connection. 相似文献
14.
By definition, the metric of N-dimensional 1-form Finsler space is constructed proceeding from, in general arbitrary, Minkowskian metric by means of an N-dimensional reference frame, i.e., in other words, by means of N independent linear 1-forms. In the present paper, the attention is drawn to the fact that a preferred osculating Riemannian space with simple but interesting properties exists for a 1-form Finsler space. Then, some significant simplifications are emphasized which are imposed by the conditions Ci=0 in a 1-form Finsler space. The T- condition and S3-likeness give rise to additional simplifications. Since the 1-form Berwald- Moór's metric exhibits all three properties mentioned above, a fairly simple expression for the curvature scalar H = Hijij of this metric may be calculated. In conclusion, the attention is drawn to the fact that the assumption of a 1-form structure of the space-time is certainly expedient in obtaining a deeper insight into the Finslerian relativity. 相似文献
15.
16.
The issue of whether teleparallel nonlinear connections exist is resolved by their explicit construction on Finslerian metrics
that arise in the Robertson test theory of special relativity (RTTSR), and on the Minkowski metric in particular. The method
is an adaptation to the Finsler bundle of a similar construction for teleparallel linear connections. It suggests the existence
of a concept of metric compatibility alternative toω
μλ
+ω
λμ
= 0 for teleparallel nonlinear connections. A sophisticated system of partial differential equations whose solutions have
been discussed in the computing literature is interpreted in geometric terms. The characteristics of the solutions are checked
against compliance with the conditionω
μλ
+ω
λμ
= 0, an issue whose relevance for this theory derives from the fact that nonantisymmetric connections repeatedly appear in
teleparallel geometry. 相似文献
17.
In this article, our aim is to consider inflation, dark energy and dark matter in the framework of a real scalar field. To
this end, we use the quintessence approach. We have tried a real scalar field with a specific self-interaction potential in
a spacially flat universe. Numerical results indicate that this potential can drive the expansion of the universe in three
distinct phases. The first phase behaves as an inflationary expansion. For this stage, setting the scalar field’s initial
value to ϕ
0≥1.94 leads to N 3 68\mathcal{N}\geq 68 favored by observation. After the inflationary phase, the scalar field starts an oscillatory behavior which averages to a
=0\bar{w}=0 fluid. This stage can be taken as a cold dark matter (p≈0) epoch expected from works on the structure formation issue. Observations and cosmological models indicate that t
inf
≈10−35 s and the matter dominated lasts for t
m
≈1017 s, hence
(\fractmtinf)obs ? 1052(\frac{t_{m}}{t_{inf}})_{obs}\approx10^{52}. We have shown that the present model can satisfy such a constraint. Finally, the scalar field leaves the oscillatory behavior
and once again enters a second inflationary stage which can be identified with the recent accelerated expansion of the universe.
We have also compared our model with the ΛCDM model and have found a very good agreement between the equation of state parameter of both of models during the DM and DE
era. 相似文献
18.
Shuvendu Chakraborty Ujjal Debnath 《International Journal of Theoretical Physics》2010,49(8):1693-1698
We have considered N-dimensional Einstein field equations in which four-dimensional space-time is described by a FRW metric and that of extra
dimensions by an Euclidean metric. We have supposed that the higher dimensional anisotropic universe is filled with only normal
scalar field or tachyonic field. Here we have found the nature of potential of normal scalar field or tachyonic field. From
graphical representations, we have seen that the potential is always decreases with field φ increases. 相似文献
19.
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
20.
K. A. Bronnikov B. E. Meierovich 《Journal of Experimental and Theoretical Physics》2008,106(2):247-264
We consider (d
0 + 2)-dimensional configurations with global strings in two extra dimensions and a flat metric in d
0 dimensions, endowed with a warp factor e
2γ depending on the distance l from the string center. All possible regular solutions of the field equations are classified by the behavior of the warp
factor and the extradimensional circular radius r(l). Solutions with r → ∞ and r → const > 0 as l → ∞ are interpreted in terms of thick brane-world models. Solutions with r → 0 as l → l
c > 0, i.e., those with a second center, are interpreted as either multibrane systems (which are appropriate for large enough
distances l
c between the centers) or as Kaluza-Klein-type configurations with extra dimensions invisible due to their smallness. In the
case of the Mexican-hat symmetry-breaking potential, we build the full map of regular solutions on the (ɛ, Γ) parameter plane,
where ɛ acts as an effective cosmological constant and Γ characterizes the gravitational field strength. The trapping properties
of candidate brane worlds for test scalar fields are discussed. Good trapping properties for massive fields are found for
models with increasing warp factors. Kaluza-Klein-type models are shown to have nontrivial warp factor behaviors, leading
to matter particle mass spectra that seem promising from the standpoint of hierarchy problems.
The text was submitted by the authors in English. 相似文献