Star-UBB Seminar Series:- Buchdahl-inspired spacetimes - How to break a six-decades-old impasse
In this talk the speaker shall revitalize an obscure program that Hans Buchdahl ventured circa 1962 in search of static spherically symmetric vacua in pure Ｒ² gravity. He proved therein that the vacua generally have non-constant scalar curvature. Unfortunately, he deemed the final step in his calculations insurmountable and suspended his further pursuit – prematurely so – and his work has largely become a “lost art” nowadays. The speaker recently broke this six-decades-old impasse and accomplished his goal and shall present three sets of vacua that are either derived from, or inspired by, the Buchdahl program: (i) An exhaustive class of metrics with non-constant scalar curvature in exact compact form for pure Ｒ² gravity; (ii) A non-Schwarzschild asymptotically flat metric in exact closed analytical form also for pure Ｒ² gravity; and (iii) A perturbative metric with non-constant curvature for Ｒ+Ｒ² gravity. These metrics project anomalous behaviours yet encountered before. The speaker shall also go over their implications in various directions, ranging from the thermodynamics of Ｒ² black holes to the Lu-Perkins-Pope-Stelle ansatz for the full quadratic action, Ｒ+Ｒ²+Weyl.
講者：Dr. Hoang Ky Nguyen (Baltimore, Maryland, USA)
Scientific and Technological Advanced Research- Babeș-Bolyai University(Star-UBB) Seminar Series in Gravitation, Cosmology and Astrophysics
Presently a period of rapid and intense change are being witnessed in our understanding of the gravitational force, at a rate that is quickly increasing since the important observational discoveries of the late 1990s. With the advent of new observational techniques, the emergence of important cosmological and astrophysical paradigms can be seen that lead to a deep change in our understanding of the Universe. Astronomical observations strongly suggest that at large scales the force of gravity may not behave according to standard general relativity, and that a generalization of the gravitational action, either at the geometric level, or at the matter level, may be required for a full understanding of the gravitational interaction.
The goal of the present seminar is to bring Theoretical Gravitational Physics closer to the observations and experiments, and to discuss current topics in general relativity, high-energy physics, astrophysics and cosmology.