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A self-similar solution of a fluid with spherical distribution in general relativity
Indian Journal of Physics ( IF 2 ) Pub Date : 2021-01-03 , DOI: 10.1007/s12648-020-01959-1
Víctor Medina

The purpose of this article is to use an algorithm to obtain a non-static solution to the Einstein–Euler equations of a spherically symmetric matter distribution of a perfect fluid. The equations obtained make up a nonlinear system of partial derivative equations (PDE), which in the vast majority of cases is quite difficult to solve, either analytically or numerically. In this context, the spherical symmetry of space-time is very useful since it allows to establish the self-similarity of the solutions. This assumption reduces the PDEs to a set of ordinary differential equations (ODE). Therefore, the self-similarity hypothesis is very powerful in the search for non-static analytical or numerical solutions. The ODEs thus established allow defining a set of variables adjusted to the boundary conditions of the spherical distribution of matter, together with an equation of state (EOS). In this work, Tolman’s V solution has been selected as EOS. Once the numerical integration has been carried out, the variables established in the ODE and some other physical variables determined in the algorithm (density, pressure, radiation, etc.) can present damped oscillations (rebounds), depending on the initial values. This behavior is similar to that found near phase transitions in condensed matter physics, but now the mass distribution plays the role of an order parameter. This result has been obtained in other simulations of numerical relativity, where the PDE obtained from the gravitational field equations are integrated and the expression of an ultrarelativistic fluid \(\left( P=\kappa \,\rho \right) \). It is important to note that there is the possibility of carrying out simulations with other EOS (with electrical charge, anisotropy, etc.) with this algorithm. Many of the calculations to obtain the field equations, such as the conservation equations, were performed using the GRTensorIII computational algebra package, running on Maple 2017; as well as some Maple routines that have been used for these types of problems.



中文翻译:

广义相对论中具有球形分布的流体的自相似解

本文的目的是使用一种算法来获得理想流体的球对称物质分布的Einstein-Euler方程的非静态解。所获得的方程组构成了偏导数方程组(PDE)的非线性系统,在绝大多数情况下,无论是解析上还是数值上,都很难解决。在这种情况下,时空的球对称性非常有用,因为它可以建立解的自相似性。该假设将PDE简化为一组常微分方程(ODE)。因此,自相似假设在寻找非静态解析或数值解中非常有力。这样建立的ODE允许定义一组变量,以适应​​物质的球形分布的边界条件,以及状态方程(EOS)。在这项工作中,托尔曼的V解决方案已被选为EOS。一旦进行了数值积分,取决于初始值,在ODE中建立的变量和在算法中确定的其他物理变量(密度,压力,辐射等)会呈现阻尼振荡(回弹)。此行为类似于在凝聚态物理中发现的接近相变的行为,但是现在,质量分布起着阶数参数的作用。在数值相对论的其他模拟中也获得了此结果,其中对从重力场方程获得的PDE进行了积分,并提出了超相对论流体的表达式 一旦进行了数值积分,取决于初始值,在ODE中建立的变量和在算法中确定的其他物理变量(密度,压力,辐射等)会呈现阻尼振荡(回弹)。此行为类似于在凝聚态物理中发现的接近相变的行为,但是现在,质量分布起着阶数参数的作用。在数值相对论的其他模拟中也获得了此结果,其中对从重力场方程获得的PDE进行了积分,并提出了超相对论流体的表达式 一旦进行了数值积分,取决于初始值,在ODE中建立的变量和在算法中确定的其他物理变量(密度,压力,辐射等)会呈现阻尼振荡(回弹)。此行为类似于在凝聚态物理中发现的接近相变的行为,但是现在,质量分布起着阶数参数的作用。在数值相对论的其他模拟中也获得了此结果,其中对从重力场方程获得的PDE进行了积分,并提出了超相对论流体的表达式 此行为类似于在凝聚态物理中发现的接近相变的行为,但是现在,质量分布起着阶数参数的作用。在数值相对论的其他模拟中也获得了此结果,其中对从重力场方程获得的PDE进行了积分,并提出了超相对论流体的表达式 此行为类似于在凝聚态物理中发现的接近相变的行为,但是现在,质量分布起着阶数参数的作用。在数值相对论的其他模拟中也获得了此结果,其中对从重力场方程获得的PDE进行了积分,并提出了超相对论流体的表达式\(\ left(P = \ kappa \,\ rho \ right)\)。重要的是要注意,使用此算法可能会与其他EOS(带电荷,各向异性等)一起进行仿真。使用GRTensorIII计算代数软件包(在Maple 2017上运行)执行了许多用于获得场方程的计算,例如守恒方程。以及一些用于此类问题的Maple例程。

更新日期:2021-01-03
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