Higher derivative scalar-tensor monomials and their classification
作者:XianGao 单位:SchoolofPhysicsandAstronomy,SunYat-senUniversity 本文刊于: 《Science China(Physics,Mechanics & Astronomy)》 2021年第0期
关键词:
scalar-tensortheory higher-derivativegraKeywords:
scalar-tensor theory,higher-derivative gravity,modified gravity
摘要
We make a full classification of scalar monomials built of the Riemann curvature tensor up to the quadratic order and of the covariant derivatives of the scalar field up to the third order. From the point of view of the effective field theory, the third or even higher order covariant derivatives of the scalar field are of the same importance as the higher curvature terms, and thus should be taken into account. Moreover, the higher curvature terms and the higher order derivatives of the scalar field are complementary to each other, of which novel ghostfree combinations may exist. We make a systematic classification of all the possible monomials,according to the numbers of the Riemann tensor and the higher derivatives of the scalar field in each monomial. A complete basis of monomials at each order is derived, of which the linear combinations may yield novel ghostfree Lagrangians. We also develop diagrammatic representations for the monomials, which may help to simplify the analysis.
基金项目:
supportedbytheNationalNaturalScienceFoundationofChina(GrantNo.11975020)