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1.
Hernando Quevedo 《General Relativity and Gravitation》2011,43(4):1141-1152
We present the Ernst potential and the line element of an exact solution of Einstein’s vacuum field equations that contains
as arbitrary parameters the total mass, the angular momentum, and the quadrupole moment of a rotating mass distribution. We
show that in the limiting case of slowly rotating and slightly deformed configuration, there exists a coordinate transformation
that relates the exact solution with the approximate Hartle solution. It is shown that this approximate solution can be smoothly
matched with an interior perfect fluid solution with physically reasonable properties. This opens the possibility of considering
the quadrupole moment as an additional physical degree of freedom that could be used to search for a realistic exact solution,
representing both the interior and exterior gravitational field generated by a self-gravitating axisymmetric distribution
of mass of perfect fluid in stationary rotation. 相似文献
2.
Static spherically-symmetric vacuum solutions of gravitation theory equations with Lagrangian f(R) are examined, where R is
a scalar curvature and f is an arbitrary function. Equations of f(R)-theories are reduced to the Einstein scenario — general
relativity theory (GRT) equations with a source in the form of a scalar field with potential — with the use of the well-known
conformal transformation. The necessary and sufficient conditions of existence of solutions admitting conformal continuations
are formulated. This means that the central singularity of the Einstein scenario is mapped into a regular sphere Strans of the Jordan scenario (that is, into the manifold corresponding to the initial formulation of the theory), and a solution
of the field equations can be smoothly continued through it. The value of curvature R on the sphere Strans corresponds to an extremum of the function f(R). Concrete examples are considered.
__________
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 46–51, September, 2005. 相似文献
3.
D. V. Karlovets 《Journal of Experimental and Theoretical Physics》2011,113(1):27-45
Polarization radiation generated when a point charge moves uniformly along a straight line in vacuum in the vicinity of media
with a finite permittivity ɛ(ω) = ɛ′ + iɛ″ and sharp boundaries is considered. A method is developed in which polarization radiation is represented as the field of
the current induced in the substance by the field of the moving charge. The solution to the problem of radiation induced when
a charge moves along the axis of a cylindrical vacuum channel in a thin screen with a finite radius and a finite permittivity
is obtained. Depending on the parameters of the problem, this solution describes various types of radiation (Cherenkov, transition,
and diffraction radiation). In particular, when the channel radius tends to zero and the outer radius of the screen tends
to infinity, the expression derived for the emitted energy coincides with the known solution for transition radiation in a
plate. In another particular case of ideal conductivity (ɛ″ → ∞), the relevant formula coincides with the known results for
diffraction radiation from a circular aperture in an infinitely thin screen. The solution is obtained to the problem of radiation
generated when the charge flies near a thin rectangular screen with a finite permittivity. This solution describes the diffraction
and Cherenkov mechanisms of radiation and takes into account possible multiple re-reflections of radiation in the screen.
The solution to the problem of radiation generated when a particles flies near a thin grating consisting of a finite number
of strips having a rectangular cross section and a finite permittivity and separated by vacuum gaps (Smith-Purcell radiation)
is also obtained. In the special case of ideal conductivity, the expression derived for the emitted energy coincides with
the known result in the model of surface currents. 相似文献
4.
An analytical solution of the Vlasov equation for the electrons and the hydrodynamic equations for the ions in a self-consistent
electric field is constructed in the quasineutral approximation. This solution is valid for a finite electron-to-ion mass
ratio. It permits describing the expansion into vacuum of a collisionless plasma with cold ions and arbitrary initial electron
velocity distribution, forming a plasmoid that is bounded and, in the general case, spherically asymmetric in space.
Pis’ma Zh. éksp. Teor. Fiz. 67, No. 8, 543–547 (25 April 1998) 相似文献
5.
When the Brans-Dicke theory is formulated in terms of the Jordan scalar field φ, the amount of dark energy is related to the mass of this field. We investigate a solution which is relevant to the late
universe. We show that if φ is taken to be a complex scalar field, then an exact solution to the vacuum equations requires that the Friedmann equation
possesses both a constant term and one which is proportional to the inverse sixth power of the scale factor. Possible interpretations
and phenomenological implications of this result are discussed. 相似文献
6.
Carlos Castro 《Foundations of Physics》2007,37(3):366-409
Two different derivations of the observed vacuum energy density are presented. One is based on a class of proper and novel
generalizations of the (Anti) de Sitter solutions in terms of a family of radial functions R(r) that provides an explicit
formula for the cosmological constant along with a natural explanation of the ultraviolet/infrared (UV/IR) entanglement required
to solve this problem. A nonvanishing value of the vacuum energy density of the order of is derived in agreement with the experimental observations. A correct lower estimate of the mass of the observable universe
related to the Dirac–Eddington–Weyl’s large number N = 1080 is also obtained. The presence of the radial function R(r) is instrumental to understand why the cosmological constant is
not zero and why it is so tiny. Finally, we rigorously prove why the proper use of Weyl’s Geometry within the context of Friedman–Lemaitre–Robertson–Walker
cosmological models can account for both the origins and the value of the observed vacuum energy density (dark energy). The
source of dark energy is just the dilaton-like Jordan–Brans–Dicke scalar field that is required to implement Weyl invariance
of the most simple of all possible actions. The full theory involving the dynamics of Weyl’s gauge field Aμ is very rich and may explain also the anomalous Pioneer acceleration and the temporal variations (over cosmological scales)
of the fundamental constants resulting from the expansion of the Universe. This is consistent with Dirac’s old idea of the
plausible variation of the physical constants but with the advantage that it is not necessary to invoke extra dimensions.
Dedicated to the loving memory of Rachael Bowers. 相似文献
7.
Ramadan M. Ali 《International Journal of Theoretical Physics》2009,48(5):1454-1458
A regular static interior solution of Einstein’s field equations representing a perfect fluid cylinder of finite radius is
presented. The solution is matched to the Levi-Civita vacuum solution at a boundary where the pressure vanishes. The density
and pressure are finite and positive inside the cylinder for a specific range of the mass parameter. The solution could thus
represent a reasonable source for the Levi-Civita metric. 相似文献
8.
T Padmanabhan 《Pramana》1991,36(3):253-269
The quantisation of a charged scalar field in an externally specified electromagnetic field, described by the vector potentialA
i=∂if withf(t,r,θ,z)=Bθ is discussed. The electromagnetic field is zero everywhere except at the origin; a singular magnetic field (Aharonov-Bohm
field) exists at the origin. The vacuum polarization around such a magnetic field is computed and the non-local behaviour
is discussed. 相似文献
9.
The role that the auxiliary scalar field φ plays in Brans–Dicke cosmology is discussed. If a constant vacuum energy is assumed
to be the origin of dark energy, then the corresponding density parameter would be a quantity varying with φ; and almost all
of the fundamental components of our universe can be unified into the dynamical equation for φ. As a generalization of Brans–Dicke
theory, we propose a new gravity theory with a complex scalar field ϕ which is coupled to the cosmological curvature scalar.
Through such a coupling, the Higgs mechanism is naturally incorporated into the evolution of the universe, and a running density
of the field vacuum energy is obtained which may release the particle standard model from the rigorous cosmological constant
problem in some sense. Our model predicts a running mass scale of the fundamental particles in which the gauge symmetry breaks
spontaneously. The running speed of the mass scale in our case could survive all existing experiments. 相似文献
10.
Y. Kimura Y. Kitahama K. Takazawa 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,38(1):203-208
Experimental set-up for studying effects of a strong magnetic field on a structure and a decay dynamics of molecules, was
designed and constructed. A vacuum chamber, in which a molecular beam propagated, was mounted in a bore of a superconducting
magnet. Laser light crossed the molecular beam in the magnetic field and excited the molecules. Fragment or parent ions produced
through sequential decay processes, were extracted by an electric field parallel to the magnetic field and detected by a microchannel
plate. By measuring the time-of-flight from the photo-excitation to the ion-detection, a species of ions —mass and charge
state— was identified. A performance of the set-up was demonstrated using the resonance enhanced multiphoton ionization process
through the
X2Π-A2Σ+ transition of nitric oxide (NO) molecules. A mass resolution m/Δm ≥180±6 was obtained in the field up to 10 T. This was
the first successful result demonstrating the sufficient mass resolution obtained by the time-of-flight technique in the strong
magnetic field up to 10 T. Parent NO+ ions were selectively detected by the mass spectrometer and the ion current was measured as a function of the frequency of
the laser light. Rotational transition lines were measured with a sufficient S/N ratio in the field up to 10 T. 相似文献
11.
It is shown that a conformally invariant scalar field can have anomalous vacuum expectation values in a Tolman universe of any kind: closed, quasi-Euclidean, or open. The anomalous vacuum expectation values lead in the initial stages of evolution of the universe to the existence of negative energy in the closed and quasi-Euclidean models if the square of the unrenormalized mass is negative and, in the open model, if the square of the unrenormalized mass is less than the square of the Planck mass. The influence of the negative energy on cosmological models of any type with and without term is investigated. It is shown that there is no singular state.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 17–20, July, 1980.We are very grateful to K. A. Bronnikov for valuable comments. 相似文献
12.
A. F. Yukin 《Russian Physics Journal》2006,49(7):699-705
A scalar field Lagrangian is considered in the curved space-time to which a Hamiltonian determining nonzero vacuum field value
is added. The initial Lagrangian can be expressed as a sum of Lagrangians for the constant scalar field component and perturbation.
The first Lagrangian can be considered as a Lagrangian for the Einstein gravitational field in vacuum. The problem of renormalization
of the constant scalar field component is investigated. It is demonstrated that in the case of conformal relation of the scalar
field to the space-time curvature, there exists a unique value of the scalar space curvature for which the field can be considered
constant (field perturbations do not result in renormalization of the constant component). This curvature value determines
the unique value of the equilibrium nuclide density. A correlation of the examined Lagrangian parameters with the integral
parameters of the Solar system is discussed.
__________
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 18–34, July, 2006. 相似文献
13.
J. Dimock 《Communications in Mathematical Physics》1998,198(2):247-281
We study the Euclidean sine-Gordon field theory on the plane with β > 16π/3 and an interaction density confined to a finite
square. For β= 4 π we construct correlation functions for the field : sin φ \colon; and show that they are equal to the pseudoscalar
―ψΓψ correlation functions for a free fermion theory with mass term confined to the finite square.
Received: 19 May 1997 / Accepted: 30 March 1998 相似文献
14.
Anatoliy K. Prykarpatsky Nikolai N. Bogolubov 《International Journal of Theoretical Physics》2012,51(1):237-245
R. Feynman’s “heretical” approach (Dyson in Am. J. Phys. 58:209–211, 1990; Dyson in Phys. Today 42(2):32–38, 1989) to deriving the Lorentz force based Maxwell electromagnetic equations is revisited, the its complete legacy is argued both
by means of the geometric considerations and its deep relation with the vacuum field theory approach devised (Prykarpatsky
et al. in Int. J. Theor. Phys. 49:798–820, 2010; Prykarpatsky et al. in Preprint ICTP, 2008, ). Being completely classical, we reanalyze the Feynman’s derivation from the classical Lagrangian and Hamiltonian points
of view and construct its nontrivial relativistic generalization compatible with the vacuum field theory approach. 相似文献
15.
A.S. Joshipura S.D. Rindani 《The European Physical Journal C - Particles and Fields》2000,14(1):85-89
We discuss an extended model which naturally leads to mass scales and mixing angles relevant for understanding both the solar and atmospheric neutrino
anomalies in terms of the vacuum oscillations of the three known neutrinos. The model uses a softly broken –– symmetry and contains a heavy scale GeV. The –– symmetric neutrino masses solve the atmospheric neutrino anomaly while breaking of –– generates the highly suppressed radiative mass scale needed for the vacuum solution of the solar neutrino problem. All the neutrino masses in the model are inversely related
to , thus providing seesaw-type of masses without invoking any heavy right-handed neutrinos. The possible embedding of the model
into an SU(5) grand unified theory is discussed.
Received: 5 August 1999 / Revised version: 18 November 1999 / Published online: 6 April 2000 相似文献
16.
17.
We have obtained a generalization of the hydrodynamic theory of vacuum in the context of general relativity. While retaining
the Lagrangian character of general relativity, the new theory provides a natural alternative to the view that the singularity
is inevitable in general relativity and the theory of a hot Universe. We show that the macroscopic source-sink motion as a
whole of ordinary (dark) matter that emerges during the production of particles out of the vacuum can be a new source of gravitational
vacuum polarization (determining the variability of the cosmological term in general relativity). We have removed the well-known
problems of the cosmological constant by refining the physical nature of dark energy associated precisely with this hydrodynamically
initiated variability of the vacuum energy density. A new exact solution of the modified general relativity equations that
contains no free (fitting) parameter additional to those available in general relativity has been obtained. It corresponds
to the continuous and metric-affecting production of ultralight dark matter particles (with mass m
0 = (ħ/c
2) $
\sqrt {12\rho _0 k}
$
\sqrt {12\rho _0 k}
≈ 3 × 10−66 g, k is the gravitational constant) out of the vacuum, with its density ρ0, constant during the exponential expansion of a spatially flat Universe, being retained. This solution is shown to be stable
in the regime of cosmological expansion in the time interval −∞ < t < t
max, when t = 0 corresponds to the present epoch and t
max= 2/3H
0
cΩ0m
≈ 38 × 109 yr at Ω0m
= ρ0/ρc ≈ 0.28 (H
0 is the Hubble constant, ρc is the critical density). For t > t
max, the solution becomes exponentially unstable and characterizes the inverse process of dark matter particle absorption by
the vacuum in the regime of contraction of the Universe. We consider the admissibility of the fact that scalar massive photon
pairs can be these dark matter particles. Good quantitative agreement of this exact solution with the cosmological observations
of SnIa, SDSS-BAO, and the decrease in the acceleration of the expansion of the Universe has been obtained. 相似文献
18.
Donato Bini Christian Cherubini Simonetta Filippi Andrea Geralico 《General Relativity and Gravitation》2009,41(12):2781-2795
An exact solution of Einstein’s equations representing the static gravitational field of a quasi-spherical source endowed
with both mass and mass quadrupole moment is considered. It belongs to the Weyl class of solutions and reduces to the Schwarzschild
solution when the quadrupole moment vanishes. The geometric properties of timelike circular orbits (including geodesics) in
this spacetime are investigated. Moreover, a comparison between geodesic motion in the spacetime of a quasi-spherical source
and non-geodesic motion of an extended body also endowed with both mass and mass quadrupole moment as described by Dixon’s
model in the gravitational field of a Schwarzschild black hole is discussed. Certain “reciprocity relations” between the source
and the particle parameters are obtained, providing a further argument in favor of the acceptability of Dixon’s model for
extended bodies in general relativity. 相似文献
19.
The existence of force-free magnetic fields in the exterior domain of some compact simply connected surface S is proved via an iteration scheme. The iteration starts with an arbitrary exterior vacuum field, which contains flux tubes
originating and ending on S. At one cross-section of such a flux tube with S an arbitrary function α is prescribed. For small values of α (in the H?lder-norm 1, λ; 0 < λ < 1) the iteration is shown
to converge to a force-free field with the prescribed values of α in a flux tube which is close to the vacuum flux tube and
α≡ 0 outside. The force-free field is close (in the H?lder- norm 1,λ) to the starting vacuum field, in particular, it has
the same field line topology, the same boundary values on S and satisfies the same decay conditions in spatial infinity. It is in general three-dimensional and requires no continuous
symmetries.
Received: 20 June 1999 / Accepted: 25 October 1999 相似文献
20.
We find an exact solution for the space-time of a global monopole by using the vacuum expectation value of the stress energy
tensor due to an arbitrary collection of conformal mass less free quantum fields as a source. In a particular situation, the
solution is shown to possess an interesting feature like ‘wormholes’ space-time. The monopole exerts no gravitational force
on the surrounding matter. 相似文献