Soumis par Anonymous le Juin 17, 2013 - 8:39am

Recently powerful techniques have emerged for performing multi-loop computations of scattering amplitudes in quantum gravity and supergravity. These techniques include generalized unitarity and the double-copy property, related to color-kinematics duality in gauge theory. Using these techniques, the ultraviolet divergence structure of N=8 supergravity, and more recently pure N=4 supergravity, have been assessed, not only in four space-time dimensions but also in higher dimensions.

Soumis par Anonymous le Mai 31, 2013 - 9:02am

Causal dynamical triangulations (CDT) define a nonperturbative path integral for quantum gravity as a sum over triangulations. Causality is enforced on the kinematical level by means of a preferred

foliation.

Soumis par Anonymous le Mai 24, 2013 - 10:54am

By way of presenting some classic and many new results, my talk will indulge shamelessly in

advertising "Causal Dynamical Triangulations (CDT)" as a hands-on approach to nonperturbative quantum gravity that reaches where other approaches currently don't. After summarizing the rationale and basic ingredients of CDT quantum gravity and some of its key findings (like the emergence of a classical de Sitter space), I will focus on some very recent results: how we uncovered the presence of a second-order phase transition (so far unique in 4D quantum

Soumis par Anonymous le Mai 23, 2013 - 1:34pm

Causal set quantum gravity is based on the marriage between the concept of causality as an organising principle more basic even than space or time and fundamental atomicity. Causal sets suggest novel possibilities for "dynamical laws" in which spacetime grows by the accumulation of new spacetime atoms, potentially realising within physics C.D. Broad's concept of a growing block universe

Soumis par Anonymous le Mai 15, 2013 - 12:23pm

Our understanding of the physical world at the most fundamental level is based on two theories: quantum theory and general relativity. They are impressively successful when each is considered on its own, but in situations where both play a role, we are reduced to puzzles and absurdity. To the great frustration of researchers, candidate theories of quantum gravity produce more puzzles than answers. We shall tour of some of the problems, focusing on the role of spacetime and causality.

Soumis par Anonymous le Mai 13, 2013 - 8:58am

Effective field

theory techniques allow reliable quantum calculations in general relativity at

low energy. After a review of these techniques, I will discuss the attempts to

define the gravitational corrections to running gauge couplings and to the

couplings of gravity itself. I will also describe an attempt to understand the

relation between the effective field theory and Asymptotic Safety in the region

where they overlap.

Soumis par Anonymous le Mai 9, 2013 - 1:31pm

Soumis par Anonymous le Mai 9, 2013 - 1:31pm

In this talk, I will discuss about the notion of quantum renormalization group, and explain how (D+1)-dimensional gravitational theories naturally emerge as dual descriptions for D-dimensional quantum field theories. It will be argued that the dynamical gravitational field in the bulk encodes the entanglement between low energy modes and high energy modes of the corresponding quantum field theory.

Soumis par Anonymous le Mai 8, 2013 - 11:00am

The existence of three generations of neutrinos and their mass mixing is a deep mystery of our universe. On the other hand, Majorana's elegant work on the real solution of Dirac equation predicted the existence of Majorana particles in our nature, unfortunately, these Majorana particles have never been observed. In this talk, I will begin with a simple 1D condensed matter model which realizes a T^2=-1 time reversal symmetry protected superconductors and then discuss the physical property of its boundary Majorana zero modes.