共查询到18条相似文献,搜索用时 156 毫秒
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认为物质的质量(能量)存在形式可分为两部分,一部分是以纯物质形式存在的,另一部分是以纯重力场形式存在的.物质质量(能量)这两种形式各自对应着相应的能量 动量张量,物质总的能量-动量张量可表示为Tμν=T(Ⅰ)μν+T(Ⅱ)μν,这里,T(Ⅰ)μν,T(Ⅱ)μν分别代表物质纯物质部分和纯重力场部分的能量-动量张量.通过类比电磁理论,定义:ωμ≡-c2gμ0/g00,并引入一个反对称张量Dμν=ωμ/xν-ων/xμ,则物质纯重力场部分的能量-动量张量为T(Ⅱ)μν=(DμρDρν-gμνDαβDαβ/4
关键词:
能量-动量张量
纯重力场
重力场方程
标量重力势
矢量重力势 相似文献
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本文把作者在前面两篇文章导出的Tc公式推广成下面形式:Tc=αωlog(ωlog/ωc)(μ*/(λ-μ*))exp{-(1+λ)/(λ-μ*)},并从线性Eliashberg方程出发,导出了计算α的方程组。α一般是λ和μ*的函数。在弱耦合极限下,由上述方程组解得,α=2γ/π,其中lnγ=C=0.5772是Euler常数。这个结果表明了,前面两篇文章得到的Tc公式在弱耦合极限下是正确的。作者进而在Einstein谱和μ*=0情形,用数值计算方法从定α的方程组算出当λ=0.23,0.25,0.38和0.48时,a的数值。结果表明,至少在0.23≤λ≤0.45区间中,α变化很小,近似等于1/1.30。此时,本文的Tc公式实际上就是Allen及Dynes修改后的经验的McMillan Tc公式。
关键词: 相似文献
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实验研究了温度对液相外延石榴石磁泡薄膜中条状普通硬磁畴壁内的垂直布洛赫线(VBL)链解体临界面内磁场区间的影响。发现存在一对特征温度T(1)0 和 T(2)0(前者比后者略低但均高于室温),在从室温到T(2)0的每个温度T下,使VBL逐渐消失的面内磁场Hip都分布于一个与T有关的区间[Hip(1)(T), Hip(2)(T)]内,称为临界面内磁场区间:Hip<Hip(1)(T)时,VBL链保持不变;Hip(1)(T)< Hip < Hip(2)(T)时,随着Hip的增加,越来越多的VBL消失;Hip > Hip(2)(T)时,所有VBL都消失。Hip(1)(T),Hip(2)(T)及Hip(2)(T)-Hip(1)(T)均随T的升高而下降,前二者分别于T(1)0 和 T(2)0降为零。比值Hip(2)(T)/Hip(1)(T)随T的升高而升高,在低温段(包括室温)升高缓慢且约为21/2,在T(1)0附近急剧升高且至T(1)0时趋于∞。对以上结果做了理论分析。
关键词: 相似文献
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给出了包含重力场贡献在内具有宇宙因子项最普遍形式的重力场方程为Rμν-gμνR/2+λgμν=8πG(T(Ⅰ)μν+T(Ⅱ)μν)/c4,这里λ为Einstein宇宙常数,T(Ⅰ)μν,T(Ⅱ)μν分别代表物质纯物质部分和纯重力场部分的能量-动量张量.物质纯重力场部分的能量-动量张量表述为T(Ⅱ)μν=(DμρDρν-gμνDαβDαβ/4)/4πG,式中Dμν的定义为Dμν=ωμ/xν-ων/xμ,ωμ≡-c2gμ0/g00.并用重力场贡献在内最普遍形式的重力场方程分别研究了几个大家所熟悉的静态和稳态重力场,像带有Einstein宇宙因子λ项球对称纯物质球外部静态度规、静态荷电球外部度规、匀速转动星体外部度规及理想纯物质星体内部静态平衡等,并进行了讨论.
关键词:
能量动量张量
重力场方程
静态重力场
稳态重力场 相似文献
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由物质场和引力场的较为广泛的拉氏函数密度及其在(εmn,ξμ)变换下的不变性出发,导出了引力场方程和自由粒子运动方程的一般形式。它们有着较为广泛的适用性。已表明广义相对论、ECSK理论及R+R2+T2型有挠引力理论等均可作为特殊情况纳入这个体系之中。
关键词: 相似文献
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作者在μ*=0情形,从Eliashberg方程解析地导出如下的Tc公式:Tc=αωlogexp{-b((1+cλ)/λ)},式中α=2γ/π,b=c=1;Inγ=C=0.5772是Euler常数。这个Tc公式只有在Tc=0.36/α(k)以下才是正确的,α是个大于1并随材料而异的常数。我们推测,当Tc超过上述范围后,Tc公式的函数结构很可能不同于McMillan Tc公式,至少α,b和c等参量不再是些不依赖于材料的常数了。
关键词: 相似文献
11.
Riccardo Goldoni 《General Relativity and Gravitation》1976,7(9):743-755
On the basis of the results of Paper I and guided by a Machian view of nature, we find new gravitational equations which are background dependent. Such equations describe a purely geometrical theory of gravitation, and their dependence on the background structure is through the total energy-momentum tensor on the past sheet of the light cone of each space-time pointx [θμν x, say], i.e., through the integral on the past sheet of the light cone ofx of the parallel transport of the energy-momentum tensor from the space-time point in which it is defined tox along the geodesic connecting the two space-time points. Following Gürsey, we assume that the source of the De Sitter metric is not the cosmological term, but, rather, the energy-momentum tensor of a “uniform distribution of mass scintillations” [T μν x, say].T μν x, indeed, turns out to be equal to the metric tensor times a constant factor. As a consequence, in any local inhomogeneity A of a space-time whose background structure is determined by the Perfect Cosmological Principle,θ μν turns out to be approximately equal to the metric tensor times a constant factor, providedT=g αβ T αβ is sufficiently small and the structure of the past sheet of the light cones of the space-time points belonging to Λ is not too much perturbed by the local gravitational field. As a consequence, in Λ the new equations approximately reduce to Einstein's equations. If one considers a “superuniverse model” in which our universe is considered as a local inhomogeneity in a De Sitter background, then from the above result there follows a fortiori the agreement of the new gravitational equations with the classical tests of gravitation. Furthermore, the dependence on the background structure is such that the new equations (i) incorporate the idea that the frame has to be fixeddirectly in connection with cosmological observations, and (ii) are singular in the absence of matter in the whole space-time. Moreover, (iii) the coupling constant turns out to be dimensionless in natural units (c=1=?), and (iv) a local inertial frame in a De Sitter background is determined by the condition that with respect to it the background structure is homogeneous in space and in time and is Lorentz invariant. 相似文献
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We consider the renormalization of Green's functions of λφ4 quantum field theory in an external gravitational field specified by the metric tensor gμν(y). Green's functions Γ(n,3) describing the interaction of j scalar particles to arbitrary order n in the gravitational field are shown to be made finite by the standard renormalizations of the flatspace theory and a renormalization of the coefficient of the improvement term in the action functional. These results in φ4 theory can be extended to all renormalizable field theories. 相似文献
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The energy-momentum tensor in spontaneously broken non-Abelian gauge field theories is studied. The motivation is to show that recent results on the finiteness and gauge independence of S-matrix elements in gauge theories extends to observable amplitudes for transitions in a gravitational field. Path integral methods and dimensional regularization are used throughout. Green's functions Γμν(j)(q; p1,…,pj) involving the energy-momentum tensor and j particle fields are proved finite to all orders in perturbation theory to zero and first order in q, and finite to one loop order for general q. Amputated Green's functions of the energy momentum tensor are proved to be gauge independent on mass shell. 相似文献
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We derive the solutions of conformally covariant coupled Dirac and scalar fields including a nonlinear fermion self-coupling term for which the conformally covariant (not the canonical, nor the symmetric) energy-momentum tensor θμν vanishes. This “vacuum” state is degenerate. 相似文献
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Eckhard Kreisel 《Annalen der Physik》1982,494(5):380-396
Conservation Laws and Topology It is shown, that for every conserved matter tensor Tνμ there exists a frame of reference haμ, orthonormalized in a given gravitational field, such that the components haνTνμ are four conserved currents. The definition of global energy-momentum connected with these currents contains as special causes the definition of inertial frames in Minkowski space as well as the definition of energy in a comoving system in presence of Killing vectors in general relativity. Given on the other hand four closed 3-forms in a space-time with non-trivial topology, one can introduce an orthonormal frame of reference haμ in such a way, that the space-time- components of the 1-forms, dual to the given 3-forms, define a symmetric matter tensor, which generates according to Einstein's equations the gravitional field. This means a partly topological definition of matter, since the non-trivially closed part of the 3-forms is determined by the topology of the manifold. 相似文献
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A previous study of the energy-momentum tensor in ?4 theory and spontaneously broken non-Abelian gauge field theories is extended here to show finiteness to all orders in perturbation theory. Divergences of Green's functions Γμν(j) (q; p1, …, pj) involving the energy-momentum tensor θμν and j particle fields are removed by counterterms of the ordinary Lagrangian plus a renormalization of the coefficient of the Callan-Coleman-Jackiw improvement term in θμν. Physically the extra renormalization means that the mean square “mass radius” of elementary spin zero particles must be specified from experiment. 相似文献
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本文求出了Eliashberg方程在T=Tc时的解,得到了下面的临界温度级数表示式:Tc=α0(μ*)(λ〈ω2〉)1/2{1+1/λα1(μ*)〈ω4>/〈ω2>2+1/λ2(α21(μ*)〈ω6>/〈ω2>3+α22(μ*)〈ω4>2/〈ω2>4) +1/λ3(α31(μ*)〈ω8>/〈ω2>4+α32(μ*)(〈ω4>〈ω6>)/〈ω2>5)+α33(μ*)〈ω4>3/〈ω2>6+…},其中α0(μ*),α1(μ*)等仅是μ*的函数。新的Tc公式表明了,Tc不仅依赖于λ、μ*和〈ω2〉,而且依赖于有效声子谱α2F(ω)的各级矩〈ω2n〉。 相似文献