Dr. Daniela Doneva's research into the theoretical and computational astrophysics of black holes and neutron stars has uncovered novel phenomena that make it possible to probe Einstein’s theory of general relativity in its most extreme regimes. For this, she will receive the Deutsche Physikalische Gesellschaft’s Gustav Hertz Award in Berlin in March 2024. The award recognizes outstanding recent work by early-career physicists.
Daniela Doneva investigates theories beyond general relativity using highly complex mathematical models and computer simulations. Her theoretical predictions are set against astrophysical observations in order to gain a better understanding of strong gravity around black holes and neutron stars.
The general theory of relativity describes the interaction between matter (including fields), space, and time. It interprets gravity as a geometric property of curved four-dimensional space-time. A "field" is something that occupies space and contains energy - electromagnetic radiation, for example, consists of waves of the electromagnetic vector field.
Data from telescopes and space missions confirm general relativity for the relatively weak gravitational fields in our solar system. But that is just the beginning. “We know there might be something more. General relativity and particle physics cannot fully explain dark matter. We are not even sure what dark energy is. So maybe this is a manifestation of our lack of understanding of general relativity on very large scales,” Doneva says.
General relativity has not been well-tested around black holes and neutron stars, which bend space-time with their extreme gravity. It may be that new fundamental fields exist in nature, similar to the newly-discovered Higgs field in particle physics. “Part of my work is devoted to examining what the effect would be if new fundamental scalar fields existed in nature. They might look very abstract, but fields are often used to explain dark energy, dark matter, the inflation of the early universe. They appear inevitable in string theory, and quantum gravity.”
Dr. Doneva has made a theoretical discovery of a new mechanism in the formation of black holes. “We have found a mechanism that triggers the accumulation of a scalar field around black holes. Practically, the huge curvature of space-time itself builds up a new energy source around a black hole; this eventually changes space-time and leads to different observational signatures,” says Doneva.
These theoretical predictions need to be tested against observations. With the rapid advance of astrophysical observations and especially the direct detection of gravitational waves, Dr. Doneva is hopeful that enough precise observations will be collected in the coming decades to enable researchers to understand the most extreme regimes of gravity in detail.
“Many people have heard of quantum gravity – the attempt to reconcile gravity and quantum theory, of string theory, and of the theories trying to unify all interactions. To understand how these bigger theories work, we must inevitably modify our understanding of general relativity,” says Doneva. “Just as Newtonian gravity broke down and gave rise to general relativity, sooner or later general relativity will give rise to a bigger theory. My job is to make small steps to such a future discovery”
Doneva is thinking in terms of millennia. “If we ever want to be able to do deep space travel, we will need to make fundamental new discoveries in gravity because now, we can only reach the limits of our solar system. Beyond that, even with the best engines and technology, it is not possible.” Dr. Doneva points out that “every fundamental physics achievement eventually becomes practical.”
For Daniela Doneva, working as a researcher and teacher often clashes with the demands of being the mother of two small children. “I don’t want to give up on any of the dreams – to have both a family and a career. But it is tough. I cannot even go to seminars or faculty meetings if my husband is not here, because everything happens in the afternoon. Daycare closes at half past three. Tübingen is getting worse and worse for women in science.”
Dr. Doneva obtained her doctorate in theoretical physics from the University of Sofia in 2012. She has been working at the University of Tübingen since then and has received support from a Humboldt Research Fellowship (2013-2015), the Margarete von Wrangell Habilitation Program (2015-2018) and the Elite Program for Postdocs (2015-2018). She has headed her own independent Emmy Noether junior research group since 2019.
