报告题目：Local spacetime effects of dark energy

报告人：张镇

报告时间: 2022年01月17日（周一） 时间:19:00-21:00

报告地点: 线上会议（腾讯会议：481-499-191）

报告摘要:

The mysterious dark energy remains one of the greatest puzzles of modern science. Current detections for it are mostly indirect. The spacetime effects of dark energy can be locally described by the  metric. Understanding these local effects exactly is an essential step towards the direct probe of dark energy. From first principles, we prove that dark energy can exert a repulsive dark force on astrophysical scales, different from the Newtonian attraction of both visible and dark matter. One way of measuring local effects of dark energy is through the gravitational deflection of light. We geometrize the bending of light in any curved static spacetime. First of all, we define a generalized deflection angle, referred to as the Gaussian deflection angle, in a mathematically strict and conceptually clean way. Basing on the Gauss-Bonnet theorem, we then prove that the Gaussian deflection angle is equivalent to the surface integral of the Gaussian curvature over a chosen lensing patch. As an application of the geometrization, we study the problem of whether dark energy affects the bending of light and provide a strict solution to this problem in the spacetime. According to this solution, we propose a method to overcome the difficulty of measuring local dark energy effects. Exactly, we find that the lensing effect of dark energy can be enhanced by 14 orders of magnitude when properly choosing the lensing patch in certain cases. It means that we can probe the existence and nature of dark energy directly in our Solar System. This points to an exciting direction to help unraveling the great mystery of dark energy.

报告人简介：

Zhen Zhang is currently an assistant professor at Institute of High Energy Physics, Chinese Academy of Sciences. Previously, he was a postdoc in theoretical particle physics at Center for High Energy Physics, Peking University. In 2015, he obtained his PhD in particle physics and nuclear physics from IHEP, CAS. His main research interests include particle physics within and beyond the Standard Model, gravity, dark energy, as well as high energy astrophysics about black hole candidates, magnetars, fast radio bursts, and gamma-ray bursts.

研究方向：

Particle physics within and beyond the Standard Model, gravity, dark energy, as well as high energy astrophysics about black hole candidates, magnetars, fast radio bursts, and gamma-ray bursts

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