Quantum Field Theory and Gravity

The present volume arose from the conference on “Quantum field theory and
gravity – Conceptual and mathematical advances in the search for a unified
framework”, held at the University of Regensburg (Germany) from September
28 to October 1, 2010. This conference was the successor of similar conferences which took place at the Heinrich Fabri Institut in Blaubeuren in 2003
and 2005 and at the Max Planck Institute for Mathematics in the Sciences
in Leipzig in 2007. The intention of this series of conferences is to bring together mathematicians and physicists to discuss profound questions within
the non-empty intersection of mathematics and physics. More specifically,
the series aims at discussing conceptual ideas behind different mathematical
and physical approaches to quantum field theory and (quantum) gravity.
As its title states, the Regensburg conference was devoted to the search
for a unified framework of quantum field theory and general relativity. On
the one hand, the standard model of particle physics – which describes all
physical interactions except gravitation – is formulated as a quantum field
theory on a fixed Minkowski-space background. The affine structure of this
background makes it possible for instance to interpret interacting quantum
fields as asymptotically “free particles”. On the other hand, the gravitational
interaction has the peculiar property that all kinds of energy couple to it.
Furthermore, since Einstein developed general relativity theory, gravity is
considered as a dynamical property of space-time itself. Hence space-time
does not provide a fixed background, and a back-reaction of quantum fields
to gravity, i.e. to the curvature of space-time, must be taken into account.
It is widely believed that such a back-reaction can be described consistently
only by a (yet to be found) quantum version of general relativity, commonly
called quantum gravity. Quantum gravity is expected to radically change our
ideas about the structure of space-time. To find this theory, it might even be
necessary to question the basic principles of quantum theory as well.
Similar to the third conference of this series, the intention of the conference held at the University of Regensburg was to provide a forum to discuss
different mathematical and conceptual approaches to a quantum (field) theory including gravitational back-reactions. Besides the two well-known paths
laid out by string theory and loop quantum gravity, also other ideas were presented. In particular, various functorial approaches were discussed, as well as
the possibility that space-time emerges from discrete structures.
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