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Geprint op :
10 december 2018

Approved FOM programme




Quantum gravity and the search for quantum spacetime (QGRAV)

Executive organisational unit


Programme management


Prof.dr. R. Loll


Cost estimate

M€ 1.2

The objective
The challenge of quantum gravity is to find a consistent theory that unifies the principles of general relativity and quantum theory. We aim to advance this search in a nonperturbative and purely quantum field-theoretic framework, by investigating how to describe the properties of quantum spacetime quantitatively at very short length scales.

Background, relevance and implementation
Quantum gravity – often considered the holy grail of theoretical high-energy physics – seeks to provide a fundamental quantum theory underlying Einstein's classical theory of general relativity that is valid on all length scales, including the very small. Similar to how the classical field theory describes the local curvature structure of classical spacetime, the corresponding quantum theory should lead to a quantitative description of the quantum properties of spacetime at very short distances, at or near the so-called Planck scale of 10-35 m. quantum gravity should identify the true microscopic degrees of freedom underlying gravitational interactions, explain how they give rise to the macroscopic universe we see around us, and how they lead to new, observable consequences beyond the realm of the classical theory. It should provide us with the tools to understand the deep quantum regime of the very early universe, to unravel some of the mysteries of black holes posed by Einstein's theory and to decide whether exotic phenomena such as wormholes in spacetime can really exist.

This programme will focus on constructing a candidate theory for quantum gravity by purely quantum field-theoretic means, building on recent advances in applying standard lattice and renormalization group methods to gravity beyond conventional perturbation theory (which is known to break down when one approaches the Planck scale). A key challenge that lies at the heart of such a construction and permeates our research projects is the construction of suitable quantum observables, which are well defined in the nonperturbative regime of the theory and can be used to characterize 'quantum spacetime' quantitatively. An important class of such observables concerns the spectral properties of quantum spacetime. An example of this is the already much-studied spectral dimension, a subject to which our consortium members have made key contributions. An important question we will address is how one can extend, unify and systematize several recent lines of investigation into quantum spacetime observables, with the ultimate aim of transcending any particular formulation of quantum gravity.

The final evaluation will be based on the self-evaluation report initiated by the programme leader and is foreseen for 2019.

Please find a research highlight that was achieved in 2013 within this FOM programme here.