Abstract
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 scalartensor 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 a Mathematica code FeynMG, which works in conjunction with the wellknown package FeynRules, to do just that: FeynMG takes as inputs the FeynRules model file for a nongravitational theory and a usersupplied gravitational Lagrangian. FeynMG provides 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 to FeynRules, either directly or by outputting an updated FeynRules model file. The Feynman rules can then be determined and output through FeynRules, using existing universal output formats and interfaces to other analysis packages.
Original language  English 

Article number  109035 
Journal  Computer Physics Communications 
Volume  296 
Early online date  6 Dec 2023 
DOIs  
Publication status  Published  1 Mar 2024 
Keywords
 Feynman rules
 Symbolic algebra
 Scalartensor theories
 High energy physics
 FeynRules
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FeynMG: A FeynRules extension for scalartensor theories of gravity
Sevillano Muñoz, S. (Contributor), Copeland, E. J. (Contributor), Millington, P. (Contributor) & Spannowsky, M. (Contributor), Mendeley Data, 19 Dec 2023
DOI: 10.17632/bjpfmtt55k.1, https://data.mendeley.com/datasets/bjpfmtt55k
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