共查询到20条相似文献,搜索用时 359 毫秒
1.
Philip D. Mannheim 《Foundations of Physics》2012,42(3):388-420
We review some recent developments in the conformal gravity theory that has been advanced as a candidate alternative to standard
Einstein gravity. As a quantum theory the conformal theory is both renormalizable and unitary, with unitarity being obtained
because the theory is a PT symmetric rather than a Hermitian theory. We show that in the theory there can be no a priori classical curvature, with all
curvature having to result from quantization. In the conformal theory gravity requires no independent quantization of its
own, with it being quantized solely by virtue of its being coupled to a quantized matter source. Moreover, because it is this
very coupling that fixes the strength of the gravitational field commutators, the gravity sector zero-point energy density
and pressure fluctuations are then able to identically cancel the zero-point fluctuations associated with the matter sector.
In addition, we show that when the conformal symmetry is spontaneously broken, the zero-point structure automatically readjusts
so as to identically cancel the cosmological constant term that dynamical mass generation induces. We show that the macroscopic
classical theory that results from the quantum conformal theory incorporates global physics effects that provide for a detailed
accounting of a comprehensive set of 138 galactic rotation curves with no adjustable parameters other than the galactic mass
to light ratios, and with the need for no dark matter whatsoever. With these global effects eliminating the need for dark
matter, we see that invoking dark matter in galaxies could potentially be nothing more than an attempt to describe global
physics effects in purely local galactic terms. Finally, we review some recent work by ’t Hooft in which a connection between
conformal gravity and Einstein gravity has been found. 相似文献
2.
R. Parentani 《International Journal of Theoretical Physics》2002,41(11):2175-2200
In the semiclassical treatment, i.e. in a classical black hole geometry, Hawking quanta emerge from trans-Planckian configurations because of scale invariance. There is indeed no scale to stop the blueshift effect encountered in the backward propagation toward the event horizon. On the contrary, when taking into account the gravitational interactions neglected in the semiclassical treatment, a new UV scale could be dynamically engendered and could stop the focusing. To show that this is the case, we use the large-N limit, where N is the number of matter fields. In this limit, the semiclassical treatment is the leading contribution. Nonlinear gravitational effects appear in the next orders and in the first of these, the effects are governed by the two-point correlation function of the energy–momentum tensor evaluated in the vacuum. In this case they can also be obtained by considering light propagation in a stochastic ensemble of metrics whose mean fluctuating properties are determined by this two-point function. 相似文献
3.
4.
Anne Magnon 《International Journal of Theoretical Physics》1992,31(6):1015-1023
The notion of local quasi-gauge bundle structure is introduced. We show that general relativity can be recast in a local quasi-SU(2)-bundle framework. In the limit of weak asymptotic gravitational field, this geometrical setup gives rise to spin-2 tensor fields sourcing global charges. If such charges are available, it is shown that the asymptotic geometrical framework is that of aU(1) gauge bundle overS
2, the commutative geometry of the (Dirac) magnetic monopole. 相似文献
5.
A. Benyoussef D. Dohmi A. El Kenz L. Peliti 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,6(4):503-510
Using a replica formalism, a generalization of a recent mean field model corresponding to the observed wrinkling transition
in randomly polymerized membranes is presented. In this model we study the effects of global fluctuations of the surface normals
to the flat membrane, which can be introduced by a random local field. In absence of these global fluctuations, we show that,
the model exhibits both continuous and discontinuous transitions between flat and wrinkled phases, contrary to what has been
predicted by Bensimon et al. and Attal et al. Phase diagrams both in replica symmetry and in breaking of replica symmetry in sense of Almeida and Thouless are given. We
have also investigated the effects of global fluctuations on the replica symmetry phase diagram. We show that, the wrinkled
phase is favored and the flat phase is unstable. For large global fluctuations, the transition between wrinkled and flat phases
becomes first order.
Received: 3 December 1997 / Revised: 31 March 1998 / Accepted: 3 August 1998 相似文献
6.
In Newtonian gravitational theory a system of point charged particles can be arranged in static equilibrium under their mutual gravitational and electrostatic forces provided that for each particle the charge,e, is related to the mass,m, bye=G
1/2
m. Corresponding static solutions of the coupled source free Einstein-Maxwell equations have been given by Majumdar and Papapetrou. We show that these solutions can be analytically extended and interpreted as a system of charged black holes in equilibrium under their gravitational and electrical forces.We also analyse some of stationary solutions of the Einstein-Maxwell equations discovered by Israel and Wilson. If space is asymptotically Euclidean we find that all of these solutions have naked singularities.Alfred P. Sloan Research Fellow, supported in part by the National Science Foundation. 相似文献
7.
Bipin Singh Koranga Rajesh Pandey 《International Journal of Theoretical Physics》2011,50(5):1468-1473
Neutrino mixing lead to a non zero contribution to the dark energy of the universe. We assume that the neutrino masses and
mixing arise through physics at a scale intermediate between Planck Scale and the electroweak scale. The mechanism of neutrino
mixing is a possible candidate to contribute the cosmological dark energy. Quantum gravitational (Planck scale) effects lead
to an effective SU(2)
L
×U(1) invariant dimension-5 Lagrangian involving neutrino and Higgs fields, which gives rise to additional terms in neutrino
mass matrix. There additional term can be considered to be perturbation of the GUT scale bi-maximal neutrino mass matrix.
We assume that the gravitational interaction is flavor. In this paper, we discuss the three flavor neutrino mixing and cosmological
dark energy contributes due to Planck scale effects. 相似文献
8.
Huei Peng 《General Relativity and Gravitation》1990,22(1):33-43
In this paper we propose a set of generalized London equations which can describe the effects of gravitational waves on a superconducting antenna. We point out that a superconducting antenna with large quality factorQ will behave differently from a normal antenna, especially in the resonant case. The expression of the signal-to-noise ratio for a superconducting antenna is derived. 相似文献
9.
The Lanczos Potential is a theoretical useful tool to find the conformal Weyl curvature tensor C
abcd
of a given relativistic metric. In this paper we find the Lanczos potential L
abc
for the van Stockung vacuum gravitational field. Also, we show how the wave equation can be combined with spinor methods
in order to find this important three covariant index tensor. 相似文献
10.
Light traveling through a liquid crystal with disclinations perceives a geometrical background which causes lensing effects
similar to the ones predicted for cosmic objects like global monopoles and cosmic strings. In this paper we explore the effective
geometry as perceived by light in such media. The comparison between both systems suggests that experiments can be done in
the laboratory to simulate optical properties, like gravitational lensing, of cosmic objects. 相似文献
11.
We show that gravitational effects of global cosmic 3-branes can be responsible for compactification from six to four space-time dimensions, naturally producing the observed hierarchy between electroweak and gravitational forces. The finite radius of the transverse dimensions follows from Einstein's equation, and is exponentially large compared with the scales associated with the 3-brane. The space-time ends on a mild naked singularity at the boundary of the transverse dimensions; nevertheless unitary boundary conditions render the singularity harmless. 相似文献
12.
In this review paper, we discuss how gravity and spin can be obtained as the realization of the local Conformal-Affine group
of symmetry transformations. In particular, we show how gravitation is a gauge theory which can be obtained starting from
some local invariance as the Poincaré local symmetry. We review previous results where the inhomogeneous connection coefficients,
transforming under the Lorentz group, give rise to gravitational gauge potentials which can be used to define covariant derivatives
accommodating minimal couplings of matter, gauge fields (and then spin connections). After we show, in a self-contained approach,
how the tetrads and the Lorentz group can be used to induce the spacetime metric and then the Invariance Induced Gravity can be directly obtained both in holonomic and anholonomic pictures. Besides, we show how tensor valued connection forms
act as auxiliary dynamical fields associated with the dilation, special conformal and deformation (shear) degrees of freedom,
inherent to the bundle manifold. As a result, this allows to determine the bundle curvature of the theory and then to construct
boundary topological invariants which give rise to a prototype (source free) gravitational Lagrangian. Finally, the Bianchi
identities, the covariant field equations and the gauge currents are obtained determining completely the dynamics. 相似文献
13.
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
14.
Wen-biao Han 《International Journal of Theoretical Physics》2009,48(3):621-629
In this paper, we calculate the gravitational waveform from free test particles around Schwarzschild black holes immersed
in a uniform strong magnetic field. By comparing with the cases of the Schwarzschild black holes, we find that for stable
circle orbits, magnetic field can amplify amplitude and frequency of gravitational waves (here after GWs). For other general
orbits, the uniform magnetic field also can amplify amplitude of GWs, enhance energy radiation of GWs and make it to shift
to higher frequency. Another obvious influence of magnetic field B is that it can change the form of h
× component of GWs. 相似文献
15.
Mark P Haugan 《Annals of Physics》1979,118(1):156-186
If the equivalence principle is violated, then observers performing local experiments can detect effects due to their position in an external gravitational environment (preferred-location effects) or can detect effects due to their velocity through some preferred frame (preferred-frame effects). We show that the principle of energy conservation implies a quantitative connection between such effects and structure-dependence of the gravitational acceleration of test bodies (violation of the Weak Equivalence Principle). We analyze this connection within a general theoretical framework that encompasses both non-gravitational local experiments and test bodies as well as gravitational experiments and test bodies, and we use it to discuss specific experimental tests of the equivalence principle, including non-gravitational tests such as gravitational redshift experiments, Eötvös experiments, the Hughes-Drever experiment, and the Turner-Hill experiment, and gravitational tests such as the lunar-laser-ranging “Eötvös” experiment, and measurements of anisotropies and variations in the gravitational constant. This framework is illustrated by analyses within two theoretical formalisms for studying gravitational theories: the PPN formalism, which deals with the motion of gravitating bodies within metric theories of gravity, and the TH?μ formalism that deals with the motion of charged particles within all metric theories and a broad class of non-metric theories of gravity. 相似文献
16.
Salvatore Capozziello Giuseppe Basini Mariafelicia De Laurentis 《The European Physical Journal C - Particles and Fields》2011,71(6):1679
We derive a geometrical approach to produce the mass of particles that could be suitably tested at LHC. Starting from a 5D
unification scheme, we show that all the known interactions could be suitably deduced as an induced symmetry breaking of the
non-unitary GL(4)-group of diffeomorphisms. The deformations inducing such a breaking act as vector bosons that, depending on the gravitational
mass states, can assume the role of interaction bosons like gluons, electroweak bosons or photon. The further gravitational
degrees of freedom, emerging from the reduction mechanism in 4D, eliminate the hierarchy problem since generate a cutoff comparable
with electroweak one at TeV scales. In this “economic” scheme, gravity should induce the other interactions in a non-perturbative
way. 相似文献
17.
Linsen Zhang Jialin Zhang Zhiying Zhu Xiangyun Fu Zhengxiang Li 《International Journal of Theoretical Physics》2010,49(5):974-978
In this paper we investigate the mass defect and other gravitational effects in noncommutative Schwarzschild space-time obtained
by considering particles as smeared objects. The effects of space-time noncommutativity on mass defect of a test particle
and a homogeneous spherical shell are calculated. The NC corrections to gravitational redshift, and light-speed in Schwarzschild
field are briefly discussed. The results show that the NC corrections have weakening action on these gravitational effects
comparing with those in commutative cases. 相似文献
18.
Lee Smolin 《General Relativity and Gravitation》1985,17(5):417-437
I show that in linearized general relativity it is impossible to construct a detector by the use of which the quantum state of the linearized gravitational field could be reliably determined. This is because there is no material satisfying the positive energy condition which can serve as a good conductor or absorber of gravitational radiation over a finite range of frequencies. If this property is true of the full theory then one can conclude that a certain proportion of both the energy and information carried by a gravitational wave is irreversibly lost, and that there is a correspondingintrinsic entropy associated with any distribution of gravitational radiation. 相似文献
19.
A geometric model for the quantum nature of interaction fields is proposed. We utilize a trivial fibre bundle whose typical
fibre has a multiconnectivity characterized by a discrete group Γ. By seeing Γ as a gauge group with global action on each
fibre, we show that the corresponding field strength is non-zero only on the future part of the light cone whose vertex is
at the interaction point. When the interaction is submitted to the symmetries of a Lie group G, we consider the gauge group G x Γ. The field strength of the gauge having this group includes a term expressing the quantization of the interaction field
described by G. This geometric interpretation of quantization makes use of topological arguments similar to those applied to explain the
Aharonov-Bohm effect. Two examples show how this interpretation applies to the cases of electromagnetic and gravitational
fields.
相似文献