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Group Leader: Dr. Daniele Oriti
This Independent Research Group is funded by the Alexander von Humboldt Foundation, through a Sofja Kovalevskaja Prize.
The research of the group aims at constructing a complete theory of quantum gravity, which is a quantum theory of gravitational phenomena and of spacetime, valid at all scales of distances and energies. In the appropriate approximation, this theory should reduce to General Relativity.
Our group works in the context of several recent approaches to this problem. In particular, we focus on Group Field Theories, Loop Quantum Gravity, Spin Foam Models, Simplicial Quantum Gravity and Matrix Models, all closely related to each other. These approaches are all background independent, in the sense that they do not assume a fixed background spacetime structure, but deal with how spacetime itself (in both its geometric and topological properties) is dynamically generated from some basic building blocks, and thus describe it as fundamentally discrete. All have obtained important results, but still present important aspects that need a better understanding and more work. One of our main lines of research concerns precisely the formal development of all of them. Also, we aim at clarifying the links between them, and try to merge the different insights that each of them provides about space and time at the Planck scale.
The main questions that all these approaches to quantum gravity have to answer, before being considered as successful, are: If spacetime is fundamentally discrete, where does the continuum spacetime we experience at low energies and macroscopic scales come from? How does such a continuum spacetime emerge from its fundamentally discrete building blocks, and end up being described by General Relativity?
Our group, therefore, works actively on the problem of extracting continuum and semi-classical (and General Relativistic) physics from the models of quantum spacetime provided by the above discrete approaches, using also mathematical tools and physical insights coming from other areas of theoretical physics. In particular, we look at analog gravity models in condensed matter physics, for examples of the transition between discrete microscopic and continuum macroscopic realms, and of the emergence of gravity (and matter) from non-gravitational systems.
Bridging the gap between our (tentative) descriptions of quantum spacetime at the Planck scale and the world as we see it also means constructing effective models of a quantum spacetime and making contact with quantum gravity phenomenology. To this aim, we study the relation between the above-mentioned approaches and effective non-commutative models of spacetime and matter in the near flat regime, and with non-commutative geometry in general. In fact, they form the basis of much of current quantum gravity phenomenology, focusing on the possibility of quantum gravity-induced deformation of relativistic dispersion relations and scattering thresholds. Finally, part of the group's research is concerned with cosmology. On the one hand, we work on the extraction of simplified quantum gravity models suitable for the description of the universe at large scales; on the other, we aim at obtaining new insights on the role that quantum gravity effects play in the early phases of the evolution of the universe – in particular close to the big bang –, and in the origin of (dark) matter and (dark) energy.
We work in very close collaboration with the other quantum gravity independent research group, led by Dr. B. Dittrich, and interact as well with the Quantum Gravity and Unified Theories division of the Albert Einstein Institute, directed by Prof. Nicolai, whose research themes, of course, overlap substantially with ours.
 Canonical and Covariant Dynamics of Quantum Gravity
 Group leader: Dr. Bianca Dittrich
Quantum Gravity & Unified Theories division
Director: Prof. Hermann Nicolai
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