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The Asymptotic Safety Program: New results and an inconvenient truth

Martin Reuter Johannes Gutenberg University Mainz

April 25, 2014

PIRSA:14040108
Gravitational RG flows on foliated spacetimes

Frank Saueressig Radboud Universiteit Nijmegen

April 24, 2014

PIRSA:14040106
One-loop renormalization in a toy model of Horava-Lifshitz gravity

Dario Benedetti Ecole Polytechnique - CPHT

April 24, 2014

PIRSA:14040105
Phases of Gravity

Petr Horava University of California, Berkeley

April 24, 2014

PIRSA:14040104
The characteristic structure of the Weyl curvature tensor and its utilization

Fan Zhang Beijing Normal University
April 24, 2014

PIRSA:14040139
Strong Gravity
On background-independent renormalization in state-sum model

Benjamin Bahr Universität Hamburg

April 24, 2014

PIRSA:14040101
13/14 PSI - Explorations in Cosmology - Lecture 13

Matthew Johnson York University

April 24, 2014

PIRSA:14040058
Global flows in quantum gravity

Jan Pawlowski Universität Heidelberg - Institut für Theoretische Physik

April 24, 2014

PIRSA:14040100
Grassmann tensor network renormalization and fermionic topological quantum field theory: a new route towards quantum gravity

Zheng-Cheng Gu Chinese University of Hong Kong

April 24, 2014

PIRSA:14040099
13/14 PSI - Explorations in Particle Theory - Lecture 13

Brian Shuve Harvey Mudd College

April 24, 2014

PIRSA:14040070
Refinement limit of quantum group spinnets

Mercedes Martin-Benito Complutense University of Madrid

April 23, 2014

PIRSA:14040098
Asymptotic safety in a pure matrix model

Jan Ambjorn University of Copenhagen

April 23, 2014

PIRSA:14040097

The Asymptotic Safety Program: New results and an inconvenient truth

Martin Reuter Johannes Gutenberg University Mainz

April 25, 2014

PIRSA:14040108

We briefly review the various components and their conceptual status of the full Asymptotic Safety Program which aims at finding a nonperturbative infinite-cutoff limit of a regularized functional integral for a quantum field theory of gravity. It is explained why in the continuum formulation based on the Effective Average Action the key requirement of background independence unavoidably results in a "bi-metric" framework, and recent results on truncated RG flows of bi-metric actions are presented. They suggest that the next generation of truncations that must be explored should be of bi-metric type. As an application, a method of characterizing and counting physical states is shown to arise.
Gravitational RG flows on foliated spacetimes

Frank Saueressig Radboud Universiteit Nijmegen

April 24, 2014

PIRSA:14040106

The role of time and a possible foliation structure of spacetime are longstanding questions which lately received a lot of renewed attention from the quantum gravity community. In this talk, I will review recent progress in formulating a Wetterich-type functional renormalization group equation on foliated spacetimes and outline its potential applications. In particular, I will discuss first results concerning the RG flow of
Horava-Lifshitz gravity, highlighting a possible mechanism for a dynamical Lorentz-symmetry restoration at low energies.
One-loop renormalization in a toy model of Horava-Lifshitz gravity

Dario Benedetti Ecole Polytechnique - CPHT

April 24, 2014

PIRSA:14040105

I will present some recent results on the UV properties of a toy model of Horava-Lifshitz gravity in 2+1 dimensions. In particular, I will illustrate some details of a one-loopcalculation, leading to beta functions for the running couplings. The renormalization group flow obtained in such way shows that Newton's constant is asymptotically free. However, the DeWitt
supermetric approaches its Weyl invariant form with the same speed and the effective interaction coupling of the scalar degree of freedom remains constant along the flow. I will discuss some general lesson that we can learn from these results.
Phases of Gravity

Petr Horava University of California, Berkeley

April 24, 2014

PIRSA:14040104

Quantum gravity with anisotropic scaling exhibits a rich structure of phases and phase transitions, dominated by multicritical behavior dependent on the spacetime dimension and the dynamical critical exponent. I will discuss some features of this phase structure, as well as its similarities and differences in comparison to the CDT approach to quantum gravity.
The characteristic structure of the Weyl curvature tensor and its utilization

Fan Zhang Beijing Normal University
April 24, 2014

PIRSA:14040139
Strong Gravity
The talk will summarize some results relating to clarifying the physical significance of the characteristic structure of the Weyl curvature tensor, and proposals for its utilization. I will begin by showing how null force-free or vacuum electrodynamic solutions experience reduced scattering by propagating along the principal null directions (GPNDs) of the spacetime, as if they were the flatter directions of the curvature tensor. Building on this observation, I will use complexified sectional curvatures to develop an analogy between the Weyl tensor and the second fundamental form of an immersed surface, and argue that, despite their name, the GPNDs are more akin to the asymptotic directions rather than the principal directions. I will also identify the ``true'' principal directions and curvatures, which has so far been under-utilized. I will then move on to propose usage for these quantities in topics related to the peeling theorem, the large scale geometry of the spacetime, the transition from the merger phase of binary black hole merger into the quasinormal mode ringdown phase, and perturbation of generic background spacetimes.
On background-independent renormalization in state-sum model

Benjamin Bahr Universität Hamburg

April 24, 2014

PIRSA:14040101

In this talk we discuss some notion of coarse graining in state-sums, most notably a class of spin foam models in their holonomy representations. We discuss the notion of scale in this context, and how diffeomorphism-invariance ties into the existence of a continuum limit. We close with an example and muse about the interplay between diffeomorphism-invariance and non-renormalizability.
13/14 PSI - Explorations in Cosmology - Lecture 13

Matthew Johnson York University

April 24, 2014

PIRSA:14040058
Global flows in quantum gravity

Jan Pawlowski Universität Heidelberg - Institut für Theoretische Physik

April 24, 2014

PIRSA:14040100

In this talk I present recent work on complete UV-IR flows for the fully momentum-dependent propagator, RG-consistent vertices, Newtons coupling and the cosmological constant. For the first time, a global phase diagram is obtained where the non-Gaussian ultraviolet fixed point of asymptotic safety is connected via smooth trajectories to an infrared fixed point with classical scaling. Physics implications as well as the extension to gauge-matter-gravity systems are discussed.
Grassmann tensor network renormalization and fermionic topological quantum field theory: a new route towards quantum gravity

Zheng-Cheng Gu Chinese University of Hong Kong

April 24, 2014

PIRSA:14040099

Recently, the development of tensor network renormalization approach has provided us a powerful tool to construct new classes of topological quantum field theories(TQFTs) in discrete space-time. For example, the Turaev Viro’s states sum constructions are fixed point tensor networks representing a special class of 2+1D TQFTs. Interestingly, the Grassmann variable generalization of tensor network renormalization approach leads to new classes of TQFTs for interacting fermion systems, namely, the fermionic TQFTs. In this talk, I will start with a fermionic topological nonlinear sigma model and discuss its corresponding new mathematics - group super-cohomology theory. Then I will explain the fermionic generalization of Dijkgraaf -Witten gauge theory by using group supercohomology theory. Finally I will show examples beyond fermionic Dijkgraaf -Witten gauge theory and discuss possible new routes towards quantum gravity.
13/14 PSI - Explorations in Particle Theory - Lecture 13

Brian Shuve Harvey Mudd College

April 24, 2014

PIRSA:14040070
Refinement limit of quantum group spinnets

Mercedes Martin-Benito Complutense University of Madrid

April 23, 2014

PIRSA:14040098

The many-building-blocks limit of spin foam models remains to be an open question. The complexity of these models makes the analysis of their possible continuum phases a very difficult task. In the last years progress in this direction has been made by considering simplified, yet featured-rich, analog models to spin foams, the so-called spin net models. These models retain the main dynamical ingredient of spin foams, namely the simplicity constraints. In this talk we will introduce spin net models based on the quantum group SU(2)_q, and we will review the use of tensor network renormalization group techniques to study their coarse graining. We will analyze the resulting phase diagram, which interestingly displays a rich structure of fixed points. Furthermore we will discuss the relation of spin nets with spin foams.
Asymptotic safety in a pure matrix model

Jan Ambjorn University of Copenhagen

April 23, 2014

PIRSA:14040097

An attempt is made to define "lines of contant physics" in CDT and relate the corresponding picture to non-trivial UV fixed points as they appear in the asymptotic safety scenario.

Title	Date	Collection	Type	Info
The Asymptotic Safety Program: New results and an inconvenient truth	2014‑04‑25	Renormalization Group Approaches to Quantum Gravity	Conference	View details
Gravitational RG flows on foliated spacetimes	2014‑04‑24	Renormalization Group Approaches to Quantum Gravity	Conference	View details
One-loop renormalization in a toy model of Horava-Lifshitz gravity	2014‑04‑24	Renormalization Group Approaches to Quantum Gravity	Conference	View details
Phases of Gravity	2014‑04‑24	Renormalization Group Approaches to Quantum Gravity	Conference	View details
The characteristic structure of the Weyl curvature tensor and its utilization	2014‑04‑24	Strong Gravity	Scientific Series	View details
On background-independent renormalization in state-sum model	2014‑04‑24	Renormalization Group Approaches to Quantum Gravity	Conference	View details
13/14 PSI - Explorations in Cosmology - Lecture 13	2014‑04‑24	13/14 PSI - Explorations in Cosmology	Course	View details
Global flows in quantum gravity	2014‑04‑24	Renormalization Group Approaches to Quantum Gravity	Conference	View details
Grassmann tensor network renormalization and fermionic topological quantum field theory: a new route towards quantum gravity	2014‑04‑24	Renormalization Group Approaches to Quantum Gravity	Conference	View details
13/14 PSI - Explorations in Particle Theory - Lecture 13	2014‑04‑24	13/14 PSI - Explorations in Particle Theory	Course	View details
Refinement limit of quantum group spinnets	2014‑04‑23	Renormalization Group Approaches to Quantum Gravity	Conference	View details
Asymptotic safety in a pure matrix model	2014‑04‑23	Renormalization Group Approaches to Quantum Gravity	Conference	View details

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