Talks

9361 - 9372 of 16763 Results

Renormalization group approach to 3d group field theory

Sylvain Carrozza University of Burgundy

April 25, 2014

PIRSA:14040112
TBA

Eun-Gook Moon Korea Advanced Institute of Science and Technology (KAIST)

April 25, 2014

PIRSA:14040142
Renormalization of entanglement entropy and the gravitational effective action

Joshua Cooperman Radboud Universiteit Nijmegen

April 25, 2014

PIRSA:14040110
13/14 PSI - Explorations in Cosmology - Lecture 14

Matthew Johnson York University

April 25, 2014

PIRSA:14040059
Why matter matters in quantum gravity

Astrid Eichhorn Universität Heidelberg

April 25, 2014

PIRSA:14040109
13/14 PSI - Explorations in Particle Theory - Lecture 14

Brian Shuve Harvey Mudd College

April 25, 2014

PIRSA:14040071
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

Renormalization group approach to 3d group field theory

Sylvain Carrozza University of Burgundy

April 25, 2014

PIRSA:14040112

I will start with a brief overview of tensorial group field theories with gauge invariant condition and their relation to spin foam models. The rest of the talk will be focused on the SU(2) theory in dimension 3, which is related to Euclidean 3d quantum gravity and has been proven renormalizable up to order 6 interactions. General renormalization group flow equations will be introduced, allowing in particular to understand the behavior of the relevant couplings in the neighborhood of the Gaussian fixed point. I will close with preliminary investigations about the existence of a non-trivial fixed point.
TBA

Eun-Gook Moon Korea Advanced Institute of Science and Technology (KAIST)

April 25, 2014

PIRSA:14040142
Renormalization of entanglement entropy and the gravitational effective action

Joshua Cooperman Radboud Universiteit Nijmegen

April 25, 2014

PIRSA:14040110

The entanglement entropy associated with a spatial boundary in quantum field theory is ultraviolet divergent, its leading term being proportional to the area of the boundary. Callan and Wilczek proposed a geometrical prescription for computing this entanglement entropy as the response of the gravitational effective action to a conically singular metric perturbation. I argue that the Callan-Wilczek prescription is rigorously justified at least for a particular class of quantum states each expressible as a Euclidean path integral. I then show that the entanglement entropy is rendered ultraviolet finite by precisely the counterterms required to cancel the ultraviolet divergences in the gravitational effective action. In particular, the leading contribution to the entanglement entropy is given by the renormalized Bekenstein-Hawking formula. These results apply to a general quantum field theory coupled to a fixed background metric, holding for arbitrary entangling surfaces with vanishing extrinsic curvature in any dimension, to all orders in perturbation theory in the quantum fields, and for all ultraviolet divergent terms in the entanglement entropy. I also reconcile these results on the entanglement entropy with the existing literature, compare them to the Wald entropy, and speculate on their interpretation and implication.
13/14 PSI - Explorations in Cosmology - Lecture 14

Matthew Johnson York University

April 25, 2014

PIRSA:14040059
Why matter matters in quantum gravity

Astrid Eichhorn Universität Heidelberg

April 25, 2014

PIRSA:14040109

I will argue that a fundamental theory of quantum gravity that is applicable to our universe must include matter degrees of freedom. In my talk I will focus on the option that these are fundamental, in contrast to low-energy effective, degrees of freedom, and must thus be included in the microscopic dynamics of spacetime.
I will present evidence that dynamical Standard Model matter is compatible with asymptotically safe quantum gravity, while several "Beyond Standard Model" scenarios are disfavored. I will also discuss how the coupling to matter opens a window into the observational quantum gravity regime.
13/14 PSI - Explorations in Particle Theory - Lecture 14

Brian Shuve Harvey Mudd College

April 25, 2014

PIRSA:14040071
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.

Title	Date	Collection	Type	Info
Renormalization group approach to 3d group field theory	2014‑04‑25	Renormalization Group Approaches to Quantum Gravity	Conference	View details
TBA	2014‑04‑25	Quantum Matter	Scientific Series	View details
Renormalization of entanglement entropy and the gravitational effective action	2014‑04‑25	Renormalization Group Approaches to Quantum Gravity	Conference	View details
13/14 PSI - Explorations in Cosmology - Lecture 14	2014‑04‑25	13/14 PSI - Explorations in Cosmology	Course	View details
Why matter matters in quantum gravity	2014‑04‑25	Renormalization Group Approaches to Quantum Gravity	Conference	View details
13/14 PSI - Explorations in Particle Theory - Lecture 14	2014‑04‑25	13/14 PSI - Explorations in Particle Theory	Course	View details
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

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