Talk detail

Participant	Smerlak, Matteo
Institution	Albert-Einstein-Institute - Am Mühlenberg 1 - Golm - - Germany

Session	GT3	Accepted	Yes	Order	2	Time	14:20
Talk	Oral abstract	Title	Brownian motion meets general relativity
Co-authors
Abstract	Diffusion phenomena are governed by the "square-root law", stating that, in normal circumstances, the spread of a diffusive substance grows like the square-root of time. By confronting Brownian motion theory to general relativity, I show that a strong gravitational field will often alter this behavior, resulting in "anomalous diffusion". This result is not a mere theoretical curiosity: it suggests that, by creating materials containing artificial gravitational fields (such as "metamaterials"), it is possible to tailor diffusive transport. This proposal can be thought of as an extension to the realm of dissipative processes of the ideas which led to the creation of "cloaking devices" in wave optics.

Session	QG1	Accepted	Yes	Order	12	Time	18:10 - 18:30
Talk	Oral abstract	Title	The shift symmetry in spin foam models of BF theory
Co-authors	Valentin Bonzom
Abstract	The spinfoam approach to quantum gravity rests on a "quantization" of BF theory using 2-complexes and group representations. I will explain why, in dimension three and higher, this "spinfoam quantization" must be amended to be made consistent with the gauge symmetries of discrete BF theory. I will discuss a suitable generalization, called "cellular quantization", which (1) is finite, (2) produces a topological invariant, (3) matches with the properties of the continuum BF theory, (4) corresponds to its loop quantization. These results significantly clarify the foundations - and limitations - of the spinfoam formalism, and open the path to understanding, in a discrete setting, the symmetry-breaking which reduces BF theory to gravity.