摘要
We attempt to clarify several aspects concemi ng the recently presented four-dimensional Ein stein-Gauss-Bonnet gravity.We argue that the limiting procedure outlined in[Phys.Rev.Lett.124,081301(2020)]generally involves ill-defined terms in the four dimensional field equations.Potential ways to circumvent this issue are discussed,alongside remarks regarding specific solutions of the theory.We prove that,although linear perturbations are well behaved around maximally symmetric backgrounds,the equations for second-order perturbations are illdefined even around a Minkowskia n background.Additi on ally,we perform a detailed analysis of the spherically symmetric solutions and find that the central curvature singularity can be reached within a finite proper time.
基金
supported by PhD contracts of the program FPU 2015 with references FPU15/02864 and FPU15/05406(Spanish Ministry of Economy and Competitiveness),respectively
supported by the Spanish Projects(FIS2017-84440-C2-1-P)(MINECO/FEDER,EU)and FIS2016-78198-P(MINECO)
the Project No.H2020-MSCA-RISE-2017 Grant No.Fun Fi CO-777740
Project No.SEJI/2017/042(Generalitat Valenciana)
the Consolider Program CPANPHY-1205388
the Severo Ochoa Grant No.SEV-2014-0398(Spain)
financial support from the Spanish Government through the project FIS2017-86497-C2-2-P(with FEDER contribution)
from the State Agency for Research of the Spanish MCIU through the"Center of Excellence Severo Ochoa"award to the Instituto de Astrofísica de Andalucía(SEV-2017-0709)。
