A matter-coupled scalar field model is presented in obtaining a scalar fifth force when the constraint of the current cosmological constant is satisfied. The interaction potential energy density between the scalar field and matter has a symmetry-breaking form with two potential wells. The cosmological constant is proven to be a value of the scalar-field's self-interaction potential energy density at the minimum of an effective matter-density-dependent potential energy density. The effective potential is a sum of the interaction potential and the self-interaction potential of the scalar field. The scalar field can stably sit at the minimum and then the time-dependent cosmological `constant' behaves like a constant. The observed cosmic acceleration can be accounted for the scalar field. The scalar field is also extrapolated to account for inflation at the inflationary era of the Universe. In this era matter fluid is relativistic and then the interaction potential wells vanish. The unconfined quintessence therefore dominates the evolution of the Universe. It is concluded that `Planck 2018 results' favour the closed space of the Universe. The reasons are not only the measured value of the current Hubble constant, but also the observed feature of a concave potential in the framework of single-field inflationary models. By invoking a pseudo-potential in the inflationary era, the concave feature can be attributed to the pseudo-potential although the self-interaction potential is a convex function. The pseudo-potential is defined by a sum of the self-interaction potential and the energy density scale of the curvature of the Universe. It is that the positive curvature leads to the concave feature of the pseudo-potential.
Fifth-Force Constraints from UV-Complete Scalar-Tensor Gravity
INAF – Osservatorio Astrofisico di Catania（意大利国家天体物理研究所卡塔尼亚天文台）；INFN, Sezione di Catania（意大利国家核物理研究所卡塔尼亚分部）；Dipartimento di Fisica e Astronomia, Università di Catania（卡塔尼亚大学物理与天文学系）
Graduate School of Advanced Science and Engineering, Hiroshima University（广岛大学先进理工学研究科）；International Center for Quantum-field Measurement Systems for Studies of the Universe and Particles (QUP), KEK（高能加速器研究机构（KEK）宇宙与粒子量子场测量系统国际中心）；Institute of Astrophysics, Central China Normal University（华中师范大学天体物理研究所）；Laboratory for Compact Object Astrophysics and Astronomical Technology, Central China Normal University（华中师范大学致密天体天体物理学与天文技术实验室）；Center for Theoretical Physics and College of Physics, Jilin University（吉林大学理论物理中心及物理学院）
