引力子三顶点与引力自能的曲率激发

基于微扰展开,计算了联络场三点Green函数及单圈引力子自能对量子Wilson圈的贡献.结果表明,引力子三顶点及引力自能将使Einstein引力获得定域曲率的激发.     

经典与量子Wilson圈泛函的计算

用微扰方法计算了Kerr联络的Wilson圈泛函(WLF)及全曲率平方型高导数引力的WLF,结果表明在h级该类型的高导数引力存在定域曲率激发.     

根据行星轨道分析引力子质量上限

按照爱因斯坦的广义相对论,引力可与无质量的引力子相联系。一种检验引力子是否真的无质量的方法,是通过对太阳系中行星运动的详细观测来计算引力子质量的上限。如果引力子质量不为零,可能意味着需要超出广义相对论的新理论。若引力以光速传播,引力子的质量mg应为零。但是如果引力子具有微小的质量,引力将具有由引力子的康普顿波长λg标志的有限力程。     

非定域夸克真空的结构和Kisslinger函数

夸克的真空凝聚是量子色动力学(QCD)研究中一个非常重要的问题.用完全穿衣服的夸克传播子研究了QCD真空性质和夸克的真空结构.计算了定域夸克的真空凝聚值,预言了夸克的真空结构.其结果与文献中的经验值相符合,也与Dyson-Schwinger方程解一致.说明参数化的夸克传播子是成功和可靠的.     

挠率、曲率及强引力模型

本文在Eeinstein方程中,引入曲率和挠率所产生的能-动张量,证明了,曲率修正导致场方程的不相容.而挠率修正强引出一个强引力的模型.这一结果与通常Poincare规范引力论认为曲率与强耦合成正比之观点大不相同.     

诱导引力理论中宇宙场的三次量子化

诱导引力与爱因斯坦引力难以用目前的实验来区分.在研究诱导引力的宇宙量子场论时,通过对宇宙场的三次量子化,发现在希格斯场的真空期待值附近,即使无任何其它物质场存在,宇宙也可以从“无”(nothing)通过量子隧道过程而创生,其创生宇宙遵从Planck分布.但这种从无到有的宇宙创生过程是无法从真空经典爱因斯坦引力理论中得到的. 关键词：     

量子引力扩展圈表象中微分同胚约束的作用

以不同方法将微分同胚约束(D约束)对扩展圈表象抽象波函数的作用特殊化到圈表象上.以Chern–Simons两点传播子乘积项为量子引力态基本片段,构造出了满足齐次D约束作用的扩展knot不变量引力态(*φ_G)ⁿ.对其中n=1,2之引力态分别进行了满足齐次D约束的具体证明;对n>2之引力态给出了一般证明.     

引力波探测展望

早在1916年，爱因斯坦在发表广义相对论时就预言引力辐射的存在．但在初期，大多数人都怀疑引力波（Gravitational　Waves）仅仅是爱因斯坦提出的引力场方程的一个近似解…而没有实质的物理效应．直到1950年代末期，从理论上证明引力波是携带能量的并可以被探测到，引力波的存在才在理论上得到了充分的确认．广义相对论预言引力波的主要特性有：在真空中以光速传播；     

爱因斯坦固体模型中的化学势疑难及其解决

一般而言,固体系统具有单一的自由能和其它热力学函数,但是有两个化学势,一个来自振子一个来自声子,前者非零而后者为零.爱因斯坦利用的是玻尔兹曼统计,发现固体原子的单个振动的配分函数可以解释成为单一频率声子气体的配分函数,其中声子的化学势为零,但是固体原子的化学势却不能解释成为声子的化学势.本文采用微正则系综,同时给出了固体原子和声子的化学势.     

曲率与运动界面发展

对界面传播速度依赖于曲率的界面发展问题进行研究,传播速度包括法向和切向,并且,在界面传播过程中全变差的变化仅依赖在曲率为零处的法向速度对曲率的导数,切向速度对全变差的变化没有影响.     

Vacuum Correlations in Quantized Gravity

The leading terms of some curvature vacuum correlation functions in n dimensional quantized higher-derivative gravity are calculated, resulting in that these correlation functions are not zero, and the relations on the graviton propagator and the vacuum correlations between the higher-derivative gravity and the R-gravity are discussed.     

Strong-Coupled Relativity Without Relativity

GR can be interpreted as a theory of evolving 3-geometries. A recent such formulation, the 3-space approach of Barbour, Foster and Ó'Murchadha, also permits the construction of a limited number of other theories of evolving 3-geometries, including conformal gravity and strong gravity. In this paper, we use the 3-space approach to construct a 1-parameter family of theories which generalize strong gravity. The usual strong gravity is the strong-coupled limit of GR, which is appropriate near singularities and is one of very few regimes of GR which is amenable to quantization. Our new strong gravity theories are similar limits of scalar-tensor theories such as Brans–Dicke theory, and are likewise appropriate near singularities. They represent an extension of the regime amenable to quantization, which furthermore spans two qualitatively different types of inner product.We find that these strong gravity theories permit coupling only to ultralocal matter fields and that they prevent gauge theory. Thus in the classical picture, gauge theory breaks down (rather than undergoing unification) as one approaches the GR initial singularity.     

Small amplitude forced fluid dynamics from gravity at T=0

The usual derivative expansion of gravity duals of charged fluid dynamics is known to break down in the zero temperature limit. In this case, fluid–gravity duality is not understood precisely. We explore this problem for a zero temperature charged fluid driven by a low frequency, small amplitude and spatially homogeneous external force. In the gravity dual, this corresponds to a time dependent boundary value of the dilaton. We calculate the bulk solution for the dilaton and the leading back reaction to the metric and the gauge fields using the modified low frequency expansion of Faulkner et al. (arXiv:0907.2694 [hep-th]). The resulting solutions are regular everywhere, establishing fluid–gravity duality to this order.     

Energy Momentum of Marder Universe in Teleparallel Gravity

In order to evaluate the energy distribution (due to matter and fields including gravitation) associated with a space-time model of cylindrically-symmetric Marder universe, we consider the Møller, Einstein, Bergmann–Thomson and Landau–Lifshitz energy and momentum definitions in the teleparallel gravity (TG). The energy-momentum distributions are found to be zero. These results are the same as a previous works of Aygün et al., they investigated the same problem in general relativity (GR) by using the Einstein, Møller, Bergmann–Thomson, Landau–Lifshitz (LL), Papapetrou, Qadir–Sharif and Weinberg’s definitions. These results support the viewpoints of Banerjee–Sen, Xulu, Radinschi and Aydo?du–Salt?. Another point is that our study agree with previous works of Cooperstock–Israelit, Rosen, Johri et al. This paper indicates an important point that these energy-momentum definitions agree with each other not only in general relativity but also in teleparallel gravity. It is also independent of the teleparallel dimensionless coupling constants, which means that it is valid not only in the teleparallel equivalent of general relativity, but also in any teleparallel model.     

On the Domain of Applicability of General Relativity

We consider the domain of applicability of general relativity (GR), as a classical theory of gravity, by considering its applications to a variety of settings of physical interest as well as its relationship with real observations. We argue that, as it stands, GR is deficient whether it is treated as a microscopic or a macroscopic theory of gravity. We briefly discuss some recent attempts at removing this shortcoming through the construction of a macroscopic theory of gravity. We point out that such macroscopic extensions of GR are likely to be nonunique and involve non-Riemannian geometrical frameworks.     

Towards constraining of the Horava–Lifshitz gravities

Recently a renormalizable model of gravity has been proposed, which might be a UV completion of General Relativity (GR) or its infra-red modification, probably with a strongly coupled scalar mode. Although the generic vacuum of the theory is anti-de Sitter one, particular limits of the theory allow for the Minkowski vacuum. In this limit (though without consideration of the strongly coupled scalar field) post-Newtonian coefficients of spherically symmetric solutions coincide with those of the General Relativity. Thus the deviations from the convenient GR should be tested beyond the post-Newtonian corrections, that is for a system with strong gravity at astrophysical scales. In this Letter we consider potentially observable properties of black holes in the deformed Horava–Lifshitz gravity with Minkowski vacuum: the gravitational lensing and quasinormal modes. We have showed that the bending angle is seemingly smaller in the considered Horava–Lifshitz gravity than in GR. The quasinormal modes of black holes are longer lived and have larger real oscillation frequency in the Horava–Lifshitz gravity than in GR. These corrections should be observable in the near future experiments on lensing and by gravitational antennas, helping to constrain parameters of the Horava–Lifshitz gravity or to discard it.     

Comprehensive solution to the cosmological constant,zero-point energy,and quantum gravity problems

We present a solution to the cosmological constant, the zero-point energy, and the quantum gravity problems within a single comprehensive framework. We show that in quantum theories of gravity in which the zero-point energy density of the gravitational field is well-defined, the cosmological constant and zero-point energy problems solve each other by mutual cancellation between the cosmological constant and the matter and gravitational field zero-point energy densities. Because of this cancellation, regulation of the matter field zero-point energy density is not needed, and thus does not cause any trace anomaly to arise. We exhibit our results in two theories of gravity that are well-defined quantum-mechanically. Both of these theories are locally conformal invariant, quantum Einstein gravity in two dimensions and Weyl-tensor-based quantum conformal gravity in four dimensions (a fourth-order derivative quantum theory of the type that Bender and Mannheim have recently shown to be ghost-free and unitary). Central to our approach is the requirement that any and all departures of the geometry from Minkowski are to be brought about by quantum mechanics alone. Consequently, there have to be no fundamental classical fields, and all mass scales have to be generated by dynamical condensates. In such a situation the trace of the matter field energy-momentum tensor is zero, a constraint that obliges its cosmological constant and zero-point contributions to cancel each other identically, no matter how large they might be. In our approach quantization of the gravitational field is caused by its coupling to quantized matter fields, with the gravitational field not needing any independent quantization of its own. With there being no a priori classical curvature, one does not have to make it compatible with quantization.     

On the role of radiation and dimensionality in predicting flow opposed flame spread over thin fuels

In this work a flame-spread model is formulated in three dimensions to simulate opposed flow flame spread over thin solid fuels. The flame-spread model is coupled to a three-dimensional gas radiation model. The experiments [1] on downward spread and zero gravity quiescent spread over finite width thin fuel are simulated by flame-spread models in both two and three dimensions to assess the role of radiation and effect of dimensionality on the prediction of the flame-spread phenomena. It is observed that while radiation plays only a minor role in normal gravity downward spread, in zero gravity quiescent spread surface radiation loss holds the key to correct prediction of low oxygen flame spread rate and quenching limit. The present three-dimensional simulations show that even in zero gravity gas radiation affects flame spread rate only moderately (as much as 20% at 100% oxygen) as the heat feedback effect exceeds the radiation loss effect only moderately. However, the two-dimensional model with the gas radiation model badly over-predicts the zero gravity flame spread rate due to under estimation of gas radiation loss to the ambient surrounding. The two-dimensional model was also found to be inadequate for predicting the zero gravity flame attributes, like the flame length and the flame width, correctly. The need for a three-dimensional model was found to be indispensable for consistently describing the zero gravity flame-spread experiments [1] (including flame spread rate and flame size) especially at high oxygen levels (>30%). On the other hand it was observed that for the normal gravity downward flame spread for oxygen levels up to 60%, the two-dimensional model was sufficient to predict flame spread rate and flame size reasonably well. Gas radiation is seen to increase the three-dimensional effect especially at elevated oxygen levels (>30% for zero gravity and >60% for normal gravity flames).     

Energy Distributions of the Szekeres Universes in Teleparallel Gravity

In order to evaluate the energy distribution (due to matter and fields including gravitation) associated with a space-time model of Szekeres class I and II metrics, we consider the Einstein, Bergmann–Thomson and Landau–Lifshitz energy definitions in the teleparallel gravity (the tetrad theory of gravitation (TG)). We have found that Einstein and Bergmann–Thomson energy distributions give the same results, Landau–Lifshitz distribution is disagree in TG with these definitions. These results are the same as a previous works of Aygün et al., they investigated the same problem by using Einstein, Bergmann–Thomson, Landau–Lifshitz (LL) and Møller energy-momentum complexes in GR. However, both GR and TG are equivalent theories that is the energy densities are the same using different energy-momentum complexes in both theories. Also, our results are support the Cooperstock’s hypothesis.     

Mapping nonlinear gravity into General Relativity with nonlinear electrodynamics

We show that families of nonlinear gravity theories formulated in a metric-affine approach and coupled to a nonlinear theory of electrodynamics can be mapped into general relativity (GR) coupled to another nonlinear theory of electrodynamics. This allows to generate solutions of the former from those of the latter using purely algebraic transformations. This correspondence is explicitly illustrated with the Eddington-inspired Born–Infeld theory of gravity, for which we consider a family of nonlinear electrodynamics and show that, under the map, preserve their algebraic structure. For the particular case of Maxwell electrodynamics coupled to Born–Infeld gravity we find, via this correspondence, a Born–Infeld-type nonlinear electrodynamics on the GR side. Solving the spherically symmetric electrovacuum case for the latter, we show how the map provides directly the right solutions for the former. This procedure opens a new door to explore astrophysical and cosmological scenarios in nonlinear gravity theories by exploiting the full power of the analytical and numerical methods developed within the framework of GR.