Quantum Gravity

This series consists of talks in the area of Quantum Gravity.

Seminar Series Events/Videos

TBA
Apr 23 2020 - 2:30pm
Room #: 400
Speaker(s):
Scientific Areas:
TBA
May 21 2020 - 2:30pm
Room #: 400
Speaker(s):
Scientific Areas:

 

Wednesday Feb 19, 2020
Speaker(s): 

We will review the gravitational formula for fine grained entropy. We will discuss how it applies to an evaporating black hole and how we can compute the entropy of Hawking radiation.

Collection/Series: 
Scientific Areas: 

 

Thursday Feb 13, 2020
Speaker(s): 

In this talk I will discuss some recent results on boundary degrees of freedom (or edge modes), and their description via an extended phase space structure containing extra boundary fields. Motivated by a slight modification of the covariant phase space formalism, I will show how the use of a boundary Lagrangian enables to include the edge modes in the phase space and to obtain their boundary dynamics. This will be illustrated on the example of Maxwell theory, where in addition the edge modes can be understood as contributing to entanglement entropy.

Collection/Series: 
Scientific Areas: 

 

 

Tuesday Dec 10, 2019
Speaker(s): 

Our earlier findings indicate the violation of the 'volume simplicity' constraint in the current Spinfoam models (EPRL-FK-KKL). This result, and related problems in LQG, promted to revisit the metric/vielbein degrees of freedom in the classical Einstein-Cartan gravity. Notably, I address in detail what constitutes a 'geometry' and its 'group of motions' in such Poincare gauge theory. In a differential geometric scheme that I put forward the local translations are not broken but exact, and their relation to diffeomorphism transformations is clarified.

Collection/Series: 
Scientific Areas: 

 

Thursday Dec 05, 2019
Speaker(s): 

In this talk, I will describe the framework of large D matrix models, which provides new limits for matrix models where the sum over planar graphs simplifies when D is large. The basic degrees of freedom are a set of D real matrices of size NxN which is invariant under O(D). These matrices can be naturally interpreted as a real tensor of rank three, making a compelling connection with tensor models. Furthermore, they have a natural interpretation in terms of D-brane constructions in string theory.

Collection/Series: 
Scientific Areas: 

 

Wednesday Dec 04, 2019
Speaker(s): 

According to the Asymptotic Safety conjecture, a (non-perturbatively)
renormalizable quantum field theory of gravity could be constructed
based on the existence of a non-trivial fixed point of the
renormalization group flow.
The existence of this fixed point can be established, e.g., via the
non-perturbative methods of the functional renormalization group (FRG).
In practice, the use of the FRG methods requires to work within
truncations of the gravitational action, and higher-derivative operators

Collection/Series: 
Scientific Areas: 

 

Thursday Nov 28, 2019
Speaker(s): 

Hopf algebra lattice models are related to certain topological quantum field theories and give rise to topological invariants of oriented surfaces. Examples are the combinatorial quantisation of Chern-Simons theory and the Kitaev model.

Collection/Series: 
Scientific Areas: 

 

Friday Nov 15, 2019
Speaker(s): 

In approaches to quantum gravity, where smooth spacetime is an emergent approximation of a discrete Planckian fundamental structure, any standard effective field theoretical description will miss part of the degrees of freedom and thus break unitarity. Here we show that these expectations can be made precise in loop quantum cosmology.

Collection/Series: 
Scientific Areas: 

 

Thursday Nov 14, 2019
Speaker(s): 

Cosmological perturbation theory has a long tradition for describing the early phases of the Universe. As the observations of the CMB radiation suggest, it is reasonable, at least as a first approximation, to implement cosmological inhomogeneities as small perturbations around homogeneous and isotropic FRW solutions. In these approaches, backreactions between the inhomogeneities and the background are usually neglected. There is an ongoing debate about how and to which extend these backreactions affect the large scale structure of the Universe.

Collection/Series: 
Scientific Areas: 

 

Wednesday Nov 13, 2019
Speaker(s): 

I will explain how dark energy in cosmology could arise from the

noisy diffusion of energy from the low energy degrees of freedom of matter (described in terms of QFT)

to the fundamental Planckian granularity (expected from quantum gravity). This

perspective leads to a natural model resolving the fine tuning problem associated to the small

value of the cosmological constant. However, recent observations suggest that the dark energy

component in our universe might not be constant and should  instead have grown from the recombination time to the present.

Collection/Series: 
Scientific Areas: 

Pages