FeynMG: A FeynRules extension for scalar-tensor theories of gravity
FeynMG: A FeynRules extension for scalar-tensor theories of gravity
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DOI：
10.1016/j.cpc.2023.109035
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发表时间：
2022-11
期刊：
影响因子：
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通讯作者：
Sergio Sevillano Muñoz;E. Copeland;P. Millington;M. Spannowsky
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作者：
Sergio Sevillano Muñoz;E. Copeland;P. Millington;M. Spannowsky
用简单的图解规则来表示相互作用量子场论的微扰展开的能力已经彻底改变了粒子物理学（和其他地方）的计算。此外，这些规则很容易自动化，这一过程促进了符号代数软件包的兴起。然而，在扩展引力理论的情况下，例如标量张量理论，有必要对拉格朗日量进行预处理以应用这种自动化，或者至少利用现有的软件管道。我们提出了一个MathematicacodeFeynMG，它与著名的包FeynRules一起工作，就是为了做到这一点：FeynMG将非引力理论的FeynRules模型文件和用户提供的引力拉格朗日作为输入。FeynMG提供的功能是插入模型文件中指定的自由度的最小引力耦合，确定额外的张量和标量自由度（引力扇区的度量场和标量场）的耦合，并预先处理得到的拉格朗日，以便它可以直接或通过输出更新的FeynRules模型文件传递给FeynRules。然后可以使用现有的通用输出格式和接口通过FeynRules确定和输出Feynman规则到其他分析软件包。程序摘要程序标题：FeynMGCPC Library程序文件链接：https：//doi.org/10.17632/bjpfmtt55k.1开发人员的存储库链接：https://gitlab.com/feynmg/FeynMGLicensing条款：MIT license编程语言：Mathematica 13.2问题性质：确定标量-张量引力理论在粒子物理标准模型及其扩展的场之间引起的额外相互作用是一项繁琐而耗时的任务，自动化已经成熟。FeynMG是一个提供这种自动化的软件包。它可以在平坦的背景周围展开时空度规，并为给定的理论执行必要的场重定义，以提供可以由费恩规则处理的形式的拉格朗日量[1]。然后可以使用FeynRules的现有功能来确定理论的Feynman规则，并以可以读入其他粒子物理分析软件包的格式输出。解决方法：（1）将FeynRules和FeynMGin加载到Mathematica。(2)加载描述给定物质扇区和拉格朗日量的模型文件。(3)使用FeynMG实现可以：（3a）附加引力扇区，并加入曲率依赖的对象，如度规、曲率标量和张量和协变导数;（3b）在引力子与物质场的相互作用中实现外尔变换或将时空度规扩展到二阶;（3c）对角化质量和动力学混合，并正则归一化动力学场。(4)将输出直接传递给FeynRule或从FeynMG输出一个新的模型文件。
The ability to represent perturbative expansions of interacting quantum field theories in terms of simple diagrammatic rules has revolutionized calculations in particle physics (and elsewhere). Moreover, these rules are readily automated, a process that has catalyzed the rise of symbolic algebra packages. However, in the case of extended theories of gravity, such as scalar-tensor theories, it is necessary to precondition the Lagrangian to apply this automation or, at the very least, to take advantage of existing software pipelines. We present aMathematicacodeFeynMG, which works in conjunction with the well-known packageFeynRules, to do just that:FeynMGtakes as inputs theFeynRulesmodel file for a non-gravitational theory and a user-supplied gravitational Lagrangian.FeynMGprovides functionality that inserts the minimal gravitational couplings of the degrees of freedom specified in the model file, determines the couplings of the additional tensor and scalar degrees of freedom (the metric and the scalar field from the gravitational sector), and preconditions the resulting Lagrangian so that it can be passed toFeynRules, either directly or by outputting an updatedFeynRulesmodel file. The Feynman rules can then be determined and output throughFeynRules, using existing universal output formats and interfaces to other analysis packages.Program summaryProgram title:FeynMGCPC Library link to program files:https://doi.org/10.17632/bjpfmtt55k.1Developer's repository link:https://gitlab.com/feynmg/FeynMGLicensing provisions:MIT licenseProgramming language:Mathematica 13.2Nature of problem:Determining the additional interactions that scalar-tensor theories of gravity induce between the fields of the Standard Model of particle physics and its extensions is a tedious and time-consuming task that is ripe for automation.FeynMGis a package that provides this automation. It can expand the spacetime metric around a flat background and perform the necessary field redefinitions for a given theory in order to provide a Lagrangian that is in a form that can be processed byFeynRules[1]. The Feynman rules for the theory can then be determined using the existing functionality ofFeynRulesand output in formats that can be read into other particle-physics analysis packages.Solution method:(1) Load bothFeynRulesandFeynMGintoMathematica. (2) Load a model file describing a given matter sector and Lagrangian. (3) Use theFeynMGimplementation to: (3a) append the gravitational sector and incorporate curvature-dependent objects, such as the metric, curvature scalars and tensors, and covariant derivatives; (3b) effect a Weyl transformation or expand the spacetime metric up to second order in graviton interactions with the matter fields; and (3c) diagonalize mass and kinetic mixings, and canonically normalize dynamical fields. (4) Pass the output directly toFeynRulesor output a new model file fromFeynMG.