Quantum Gravity LABORATORY is interested in various semi-classical and quantum gravity proposals, and their interfaces.

## Theoretical studies

In the literature analogue gravity/effective spacetimes refers to a broad class of systems where perturbations propagate on an effective (d+1) dimensional spacetime geometry. This is a strong physical analogy not only a conceptual one. It is not a phenomenon occurring in just one particular system, but instead we know of a large number of systems that exhibit such behavior.

For example the study of waves traveling on the surface of water draining in a bathtub sheds light into the way black holes lose mass and angular momentum. What is suggested here is a combined theoretical and experimental exploration of analogue systems. In particular, we propose to investigate theoretical aspects of well-established analog systems, and attempt to identify new such systems, and last but not least combine the output of the theoretical and experimental exploration.

In order to contribute to the ongoing experiments, we are also developing suitable detection methods, e.g. 1D and 2D surface wave detection mtethods for analoge gravity experiments in open channel flows, see for example __exp1__ and __exp3__.

A literature list for analogue gravity can be found on site.

###### Analogue gravity [thy1]

The first serious effort to implement discretized geometries into the framework of general relativity dates back to 1961 and the development of Regge calculus [1]. Since then there has been persistent interest in a variety of discrete quantum gravity models [2]. One partic- ularly interesting variant is causal dynamical triangula- tions (CDT) [3], in which a geometry emerges as the sum of all possible triangulations (modulo diffeomorphisms) obeying a global time foliation. The sum is evaluated us- ing the path-integral formalism, such that every history is weighted using a variant of Regge calculus, where the edge lengths of the fundamental building blocks, the d+1 dimensional simplices, is kept fixed. The various different histories can be viewed as all possible fluctuations in the geometry, and they differ in the number of simplices and in the manner the latter are glued together. In a discrete model, such as CDT, part of the chal- lenge is to find suitable probes for the continuum limit.

We are interested in exploring the continum limit of CDT, and its connection to other branches of physics.

[1] T. Regge, Nuovo Cimento A 19,

**558** (1961).

[2] R. M. Williams, J. Phys. Conf. Ser. 33,

**38** (2006).

[3] J. Ambjorn and R. Loll, Nucl. Phys. B 536,

**407** (1998).

###### Discrete gravity [thy2]

###### Quantum gravity interfaces [thy3]

We are interested in the connection between quantum gravity and other branches of physics, such as __quantum information__ and __condensed matter physics__.

Besides establishing new connections accross various areas of phyiscs, we are interested in finding connections between the various quantum gravity candiates, such as __Causal Dynamical Triangulation and Horava-Lifshitz Gravity__.

Last but not least, we are exploring the possiblity of finding analogue discrete quantum gravity systems.