Public lecture “Gravity: The Final Frontier? The search for quantum gravity on largest and smallest scales”

The public lecture of the international conference “Metric-Affine Frameworks for Gravity 2024” will be held on Tuesday, 18 June at 18:15 in the Tartu Old Observatory. Dr. Christian Pfeifer will talk on the topic “Gravity: The Final Frontier? The search for quantum gravity on largest and smallest scales”.

We will explore this question and the nature of gravity in two steps.

First, I will explain the nature of gravity, from its classical roots in Newtonian mechanics to our current geometric understanding in terms of general relativity, including its three most important questions: What is dark matter? What is dark energy? How does quantum gravity work?

Second, we will embark on a search for signatures of quantum gravity. Since a fundamental theory of quantum gravity is still elusive, researchers have developed models that effectively capture some, but possibly not all, of the expected aspects of quantum gravity. This is analogous to describing what happens to light when it passes through a medium such as a crystal. Effective, approximately correct predictions for experiments can be made without describing the fundamental interaction of light with all the constituents of the medium. These descriptions are perfectly adequate for many experimental setups and observations. We will understand that when we apply a similar strategy, called effective quantum gravity or quantum gravity phenomenology, to the propagation of high-energetic light (gamma rays) or neutrinos in quantum spacetime, it leads to energy-dependent arrival times and gravitational lensing, which can be tested in observations on cosmic scales. At laboratory scales, we will see that phenomenological models of quantum gravity predict changes in the measurement of the lifetime of fundamental particles and effects on local quantum systems. These phenomenological predictions, which can already be used in today's experiments, serve as a guide for the construction of a fundamental theory of quantum gravity, since any fundamental theory must satisfy the limits or detections already found at the phenomenological level.

Dr. Christian Pfeifer is a postdoctoral researcher at the ZARM (Center of Applied Space Technology and Microgravity) Institute of the University of Bremen, whose research focuses on understanding the gravitational interaction. In his work, he focuses on the intersection of theoretical/mathematical physics and phenomenology, using consistent and rigorous mathematics to guarantee the reliability of physical predictions. A main goal of his research is to predict observables from modified theories of gravity and from phenomenological models of quantum gravity. The main hypothesis of his research is that the understanding of gravity can be improved by going beyond general relativity to describe the gravitational interaction. Technically, this means going beyond the usual spacetime geometry subject to the Einstein equations as the geometry of spacetime. Before his current position, Dr. Pfeifer was a postdoctoral researcher at the University of Tartu from 2017-2020. Since then, he has been part of the organization committee of the international Geometric Foundations of Gravity conferences in Tartu. Moreover, he organized several additional conferences and schools in Germany, Spain, Serbia, and Croatia and is involved in leading European wide networks of scientists.

Everybody is welcome. Entrance is free.

Public lectures of earlier conferences:

  • Prof. Mairi Sakellariadou (London) Early Universe cosmology: a primer 20 June 2023 (UTTV recording)
  • Prof. Davi Rodrigues (Espírito Santo) Why do galaxies rotate? 28 June 2022 (BBB recording)
  • Prof. Escamilla Rivera (Mexico) How a dispute over a single number became a cosmological crisis 29 June 2021 (BBB recording)
  • Prof. Emmanuel Saridakis (Athens) Black holes and gravitational waves 16 June 2020 (BBB recording)
  • Prof. Lavinia Heisenberg (Zurich) Our dark Universe 18 June 2019
  • Prof. Salvatore Capozziello (Naples) Time travel, black holes and wormholes 26 June 2018
  • Prof. Robin Tucker (Lancaster) Beyond gravity 29 August 2017

The public lecture of the international conference “Geometric Foundations of Gravity 2023” will be held on Tuesday, 20 June at 18:15 in the Tartu Old Observatory. Prof. Mairi Sakellariadou will talk on the topic “Early Universe Cosmology: a primer”.

I will give an overview of our current understanding of early universe cosmology. I will present the successes and open problems of the standard cosmological model and the role of observations and experiments against which we test our theories. I will discuss the interplay between astrophysics, high energy physics and theories of gravity aiming at unravelling the mysteries of our universe and I will highlight the need for a theory that will encompass quantum mechanics and general relativity.

Mairi Sakellariadou is a theoretical physicist working in particle physics, gravitation and cosmology, with a focus on the physics of the early universe. She studied mathematics at the University of Athens and then astrophysics at the Institute of Astronomy at the University of Cambridge. She received her PhD from Tufts University in Massachusetts. After postdoctoral studies at the Université Pierre et Marie Curie in Paris, the University of Zurich, the University of Geneva and CERN, she became an associate professor at the University of Athens. In 2005 she joined King's College as an Associate Professor and in 2011 was appointed Professor of Theoretical Physics there. She is the chairman of the "Gravitational Physics" section of the European Physical Society, and the current President-Elect of the Society. She is a member of several collaborative projects and consortia, including the LIGO research collaboration, the LISA consortium and the MoEDAL experiment.