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The European Research Council (ERC) has awarded prestigious Advanced Grants to UvA professors Jan de Boer and Daniel Bonn. The grant, which totals 2.5 million euros for each project, is awarded on the basis of the scientific excellence of the researcher and the research proposal. De Boer’s project will focus on finding the properties of quantum gravity. Bonn will study the local stresses in complex systems and materials.

Jan de Boer

Properties of quantum gravity

Jan de Boer is professor of Theoretical Physics. His project is titled Can I see Quantum Gravity? (CanISeeQG)

For more than a century, the interplay between two of the most important building blocks of nature, quantum mechanics and gravity, has been a source of inspiration for theoretical physicists. It has led to discoveries such as the Hawking radiation emitted by black holes and the development of theoretical models such as string theory. Knowledge about the interplay between quantum mechanics and gravity also produced the insight that at the most fundamental level physics is governed by the rules of quantum mechanics, while gravity is actually a phenomenon that emerges at a larger scale as an effective, ‘average’ description of the underlying quantum effects. Such quantum effects are frequently ‘non-local’: what happens in one place may be directly related to something that happens entirely elsewhere. At the same time, the description of gravity used by physicists – Einstein’s theory of general relativity – is local, also when it is applied in effective field theories.

With the recent discovery of gravitational waves and the various ongoing and upcoming experiments that will put general relativity to the test, it has become urgent, according to De Boer, to assess the validity of the standard framework of effective field theory for describing observable quantum gravity effects. Recent developments in resolving the information paradox – a puzzle resulting from the question about whether Hawking radiation released by black holes contains information – and in understanding the further quantum nature of black holes have led to the conclusion that the concept of effective field theory must be modified in order to be able to describe quantum gravity. 

De Boer will come to a precise and quantitative description of these changes, ultimately connecting it to potential experimental discoveries. In order to achieve this goal, his research employs a combination of thermodynamics, hydrodynamics and quantum information theory.

Daniel Bonn
Daniel Bonn

Local dynamics of complex liquids and systems

Daniel Bonn is professor of Complex Liquids. His project is titled Probing Stresses at the Nanoscale (NANOSTRESS).

The physics of solid materials is full of unsolved problems. Mechanical friction in engines, machines and industrial processes is an immense global source of energy loss, but is still poorly understood scientifically. The transition of materials to a glassy structure (glass transition) is perhaps the most important unsolved problem in condensed matter physics. Rheology, the study of flow properties of complex fluids, is a third ubiquitous and poorly understood phenomenon. Friction, the glass transition and rheology share a common feature in that their macroscopic mechanical behaviour results from a complex interplay between microscopic stresses that remain ill understood. This presents a major obstacle in the engineering of, for example, ball bearings, plastics and foodstuffs.

Bonn will open a window on the study of local stresses in complex materials, based on recent developments in fluorescence microscopy. Recent research has led to the development of novel molecules whose fluorescence properties depend strongly on the environment, notably on their local stresses or their spatial confinement. With these local sensors, Bonn aims to develop innovative methods to tackle the aforementioned fundamental scientific problems. He will probe these down to the nanometre length scale and with unprecedented temporal resolution.

This will allow Bonn to achieve three breakthrough results: (1) locally measuring stresses in a frictional contact; (2) the local measurement of the change of viscosity or density  for the glass transition; (3) visualising and quantifying stress transmission in flowing complex fluids in order to describe microscopically the behaviour of such fluids. By probing the local flow dynamics of complex fluids in greater detail than was previously possible, Bonn’s project will solve some of the toughest problems in non-linear physics and (statistical) mechanics, with far-reaching engineering consequences.