论文标题
$φ$敌对:用有限元方法筛选Vainshtein
$φ$enics: Vainshtein screening with the finite element method
论文作者
论文摘要
在修改后的重力理论的景观中,了解筛查机制的行为和开发测试的进展受到所涉及的田间方程的复杂性的阻碍,这些场方程在本质上是非线性的,并以较大的规模层次结构进行了表征。 Vainshtein筛选尤其如此,其中第五力被高阶导数项所抑制,该术语占主导地位,而在半径内占主导地位,远大于源的尺寸,即称为Vainshtein Radius。 在这项工作中,我们介绍了基于Fenics Library建立的数值代码$φ$ enics,以从两种感兴趣的筛选理论中求解全部运动方程:一种在运动方程中包含高阶导数操作员的模型,一个模型在两个耦合标量场中以非线性自我互动为特征。我们还包括允许标量字段的高阶运算符在后处理中计算的功能,使我们能够检查我们发现的配置文件是否是有效字段理论中的一致解决方案。这两个示例说明了试图以数值模拟这些理论时经历的不同挑战,我们展示了这些代码中如何解决这些理论。本文中的示例假设球形对称性,但是这些技术可以直接推广到非对称配置。因此,本文还提供了一个有效的示例,说明了如何使用有限元方法求解筛选的运动方程。 $φ$ enics已公开可用,可以改编以解决其他筛选理论。
Within the landscape of modified theories of gravity, progress in understanding the behaviour of, and developing tests for, screening mechanisms has been hindered by the complexity of the field equations involved, which are nonlinear in nature and characterised by a large hierarchy of scales. This is especially true of Vainshtein screening, where the fifth force is suppressed by high-order derivative terms which dominate within a radius much larger than the size of the source, known as the Vainshtein radius. In this work, we present the numerical code $φ$enics, building on the FEniCS library, to solve the full equations of motion from two theories of interest for screening: a model containing high-order derivative operators in the equation of motion and one characterised by nonlinear self-interactions in two coupled scalar fields. We also include functionalities that allow the computation of higher-order operators of the scalar fields in post-processing, enabling us to check that the profiles we find are consistent solutions within the effective field theory. These two examples illustrate the different challenges experienced when trying to simulate such theories numerically, and we show how these are addressed within this code. The examples in this paper assume spherical symmetry, but the techniques may be straightforwardly generalised to asymmetric configurations. This article therefore also provides a worked example of how the finite element method can be employed to solve the screened equations of motion. $φ$enics is publicly available and can be adapted to solve other theories of screening.