Dynamical dimensional reduction and Asymptotic Safety
The effective average action approach to Quantum Einstein Gravity (QEG) is discussed as a natural framework for exploring the scale dependent Riemannian geometry and multifractal micro-structure of the effective spacetimes predicted by QEG. Their fractal properties are related to the functional RG flow on theory space, and the special role of the running cosmological constant is emphasized. The prospects of an experimental verification will also be discussed.
Vanishing dimension: theory and phenomenology
Lower-dimensionality at higher energies has manifold theoretical
advantages as recently pointed out. Moreover, it appears that
experimental evidence may already exists for it - a statistically
significant planar alignment of events with energies higher than TeV has
been observed in some earlier cosmic ray experiments. If this alignment
is not a fluke, then the LHC should be able to see effects associated
with the dimensional crossover. Further, (2+1)-dimensional spacetimes
have no gravitational degrees of freedom, and gravity waves cannot be
produced in that epoch in the early universe. This places a universal
maximum frequency at which primordial gravity waves can propagate, which
may be accessible to future gravitational wave detectors such as LISA.
In this talk, the theoretical motivation for "vanishing dimensions" as
well as generic experimental and observational signature will be