PHYS Seminar: “Short and Long Distance Problems of General Relativity and Possible Solutions”, Bayram Tekin, 2:30PM May 17 2024 (EN)

Bayram Tekin

“Short and Long Distance Problems of General Relativity and Possible Solutions”


General Relativity, as a theory of gravity, works remarkably well at Solar system tests, yet it has to be modified to describe the motion of stars in spiral galaxies and the motion of galaxies in galaxy clusters. The problem is that stars and galaxies move too fast and contradict the predictions of both Newtonian and Einsteinian gravity theories. To explain these motions, a lot of dark matter is assumed to exist which has escaped detection so far since 1930s. General Relativity cannot also explain the observed accelerated expansion of the Universe without assuming the existence of dark energy that constitutes about 95 % of all energy in the Universe. It is not clear how to detect dark energy. The above problems are long distance problems; for short distances, General Relativity predicts singularities (such as the Big Bang singularity and the black hole singularity) which are expected to be avoided in a quantum version of the theory, that is Quantum Gravity. The theory has a name but no equations so far. I shall discuss these problems and possible alternative theories.

Bayram Tekin studied physics at METU as an undergraduate student in the Advanced Physics Section in 1991-1994. Then, in the years 1994, 1999, he did his PhD in the Physics and Astronomy department of the University of Minnesota, Minneapolis. He moved to Oxford University, UK, to work, in the years 1999-2001, as a Postdoctoral Researcher and a tutor at Balliol College. In 2001, he moved to Brandeis University, Boston, to work as a postdoc for 2 more years before accepting a faculty job at METU in 2003. Since 2011, Tekin has been teaching as a full professor at METU. His main interests have been in extended theories of gravity, black hole physics and formal aspects of quantum field theories. He has taught 13 different graduate courses at METU. He was selected by students as the 2012 Lecturer of the year and received the Mustafa Parlar foundation award for this. In 2023, he was selected by the APS as an Outstanding Referee, a lifetime award, for Phys. Rev, journals. Tekin was also awarded the TUBITAK Teşvik and GEBIP Young Scientist awards. He has published 120 research papers and advised around 40 graduate students in their master and Phd theses. He is involved in outreach programs, such as giving courses in Nesin Mathematic Village and writing popular articles describing scientific ideas. He is a writer at and evrimagaci and cowrote a book on metric theories of gravity.

Date: May 17, 2024 Friday
Time: 14:30
Place: SA-240

All interested are cordially invited.