学术报告（2023年9月20日15：00）：从外尔引力到暗能量——物质与曲率的共形不变耦合

主持人：张宏浩 教授

报告简介：We investigate the coupling of matter to geometry in conformal quadratic Weyl gravity, by assuming a coupling term of the form LmR~ 2 , where Lm is the ordinary matter Lagrangian, and R ~ is the Weyl scalar. The coupling explicitly satisfies the conformal invariance of the theory. By expressing R~ 2 with the help of an auxiliary scalar field and of the Weyl scalar, the gravitational action can be linearized, leading in the Riemann space to a conformally invariant f (R ,Lm) type theory, with the matter Lagrangian nonminimally coupled to the Ricci scalar. We obtain the gravitational field equations of the theory, as well as the energy-momentum balance equations. The divergence of the matter energy-momentum tensor does not vanish, and an extra force, depending on the Weyl vector, and matter Lagrangian is generated. The generalized Poisson equation is derived, and the Newtonian limit of the equations of motion is considered in detail. The perihelion precession of a planet in the presence of an extra force is also considered, and constraints on the magnitude of the Weyl vector in the Solar System are obtained from the observational data of Mercury. The cosmological implications of the theory are considered for the case of a flat, homogeneous and isotropic Friedmann-Lemaitre-Robertson-Walker geometry, and it is shown that the model can give a good description of the observational data for the Hubble function up to a redshift of the order of z ≈3.。

报告人简介：Tiberiu Harko博士毕业于罗马尼亚克鲁日纳波卡的巴比什-波雅依大学并获得了物理的硕士学位，并于2001年在香港大学获得了理论天文学的博士学位，导师为K.S.Cheng教授。在香港大学的博士后阶段之后，他在香港大学作为研究助理教授一直工作到2012年。同年他还加入了伦敦大学学院的数学系担任高级研究助理，以及在中山大学作为访问教授直到2019年。现今Harko博士是罗马尼亚巴比什-波雅依大学高等科技研究所的研究员。Harko博士的主要科研兴趣领域是修正引力理论、宇宙学、天文学和数学物理。