General Relativity & Quantum Cosmology

Displaying 1381 - 1392 of 1864

Asymptotic Symmetries of Gauge and Gravity Theories in Minkowski Space

Andrew Strominger Harvard University
March 13, 2014

PIRSA:14030087
General Relativity & Quantum Cosmology
A one-dimensional action for simplicial gravity in three dimensions

Wolfgang Wieland University of Erlangen-Nuremberg
March 06, 2014

PIRSA:14030088
General Relativity & Quantum Cosmology
Sequestering Lorentz violation in the Lifshitz sector

Maxim Pospelov University of Minnesota
March 06, 2014

PIRSA:14030092
General Relativity & Quantum Cosmology
Nonlocal cosmology

Richard Woodard University of Florida
February 27, 2014

PIRSA:14020137
General Relativity & Quantum Cosmology
À la recherche du temps perdu - Templeton Frontiers Colloquia

Flavio Mercati University of Naples Federico II
February 26, 2014

PIRSA:14020100
General Relativity & Quantum Cosmology
Quantum Raychaudhuri equation

Saurya Das University of Lethbridge
February 20, 2014

PIRSA:14020130
General Relativity & Quantum Cosmology
Causality, holography, and entanglement entropy
February 20, 2014

PIRSA:14020146
General Relativity & Quantum Cosmology

High Energy Physics

Condensed Matter

General Relativity & Quantum Cosmology
Non equilibrium thermodynamic of gravitational screens

Laurent Freidel Perimeter Institute for Theoretical Physics
February 19, 2014

PIRSA:14020144
General Relativity & Quantum Cosmology

Mathematical Physics
Firewall evasion by quantum gravity

Ted Jacobson University of Maryland, College Park
February 13, 2014

PIRSA:14020136
General Relativity & Quantum Cosmology
On null singularities in general relativity

Mihalis Dafermos Princeton University
February 13, 2014

PIRSA:14020133
General Relativity & Quantum Cosmology
The Radius of Neutron Stars and the Dense Matter Equation of State

Robert Rutledge McGill University
February 06, 2014

PIRSA:14020087
General Relativity & Quantum Cosmology
Black hole entropy and the case for self-dual loop quantum gravity
January 29, 2014

PIRSA:14010098
General Relativity & Quantum Cosmology

Asymptotic Symmetries of Gauge and Gravity Theories in Minkowski Space

Andrew Strominger Harvard University
March 13, 2014

PIRSA:14030087
General Relativity & Quantum Cosmology
We argue that the infinite-dimensional BMS symmetry discovered by Bondi et. al in the 60s provides an exact symmetry of the quantum gravity S-matrix. The Ward identity of this symmetry is shown to be precisely Weinberg's soft graviton theorem, also discovered in the 60s. A parallel infinite-dimensional symmetry is found to be generated in nonabelian gauge theories by gauge transformations which go to an angle-dependent finite constant at null infinity. The Ward identity of this symmetry is shown to be the soft gluon theorem.
A one-dimensional action for simplicial gravity in three dimensions

Wolfgang Wieland University of Erlangen-Nuremberg
March 06, 2014

PIRSA:14030088
General Relativity & Quantum Cosmology
Loop quantum gravity has a spinorial representation. Spinors simplify the symplectic structure of the theory, but can they also teach us something about the dynamics? We study this question in three dimensions, and derive the Ponzano–-Regge model from a spinorial action. Our construction starts from the first-order Palatini formalism, and gives the discretised action in the spinorial representation. A one-dimensional refinement limit brings us back to a continuum theory. The three-dimensional action turns into a line integral over the edges of the discretisation. We compute the gauge-fixed path integral for a generic simplicial discretisation. The resulting amplitudes reproduce the Ponzano–-Regge model.
Sequestering Lorentz violation in the Lifshitz sector

Maxim Pospelov University of Minnesota
March 06, 2014

PIRSA:14030092
General Relativity & Quantum Cosmology
Horava's proposal to use Lifshitz propagators for gravitons above certain energy scales may provide a viable theory of quantum gravity without further need of UV completion. In my talk, I will address the question of whether the complete lack of Lorentz invariance above a certain energy scale is a big problem for any realistic construction. I will argue that it is not, provided that the onset of Lifshitz scaling for gravitons occurs at momentum scale much lower than the Planck mass. I will also discuss consequences of combining Lifshitz gravity and supersymmetric matter sector.
Nonlocal cosmology

Richard Woodard University of Florida
February 27, 2014

PIRSA:14020137
General Relativity & Quantum Cosmology
I review a class of nonlocally modified gravity models which were proposed to explain the current phase of cosmic acceleration without dark energy. Among the topics considered are deriving causal and conserved field equations, adjusting the model to make it support a given expansion history, why these models do not require an elaborate screening mechanism to evade solar system tests, degrees of freedom and kinetic stability, and the negative verdict of structure formation. Although these simple models are not consistent with data on the growth of cosmic structures many of their features are likely to carry over to more complicated models which are in better agreement with the data.
À la recherche du temps perdu - Templeton Frontiers Colloquia

Flavio Mercati University of Naples Federico II
February 26, 2014

PIRSA:14020100
General Relativity & Quantum Cosmology
Augustine of Hippo declared he knew what time is until someone asked him. After 16 centuries we still largely ignore the true essence of time, but we made definite progress in studying its properties. The most striking, and somewhat intuitively (and tragically) obvious one is the irreversibility of its flow. And yet, our fundamental theories are time-reversal invariant, they do not distinguish between past and future. This is usually accounted for by assuming an immensely special initial condition of the Universe, dressed with statistical arguments. In this talk, I will show how an irreversible behaviour, and with it a growth of complexity and information, can emerge from time-reversal invariant laws, without assuming any special initial condition and without thermodynamical arguments. This phenomenon is present in General Relativity, our most advanced theory of the Universe. This irreversibility will also allow me to propose a solution of another puzzle associated with time, namely the incompatibility between the quantum and the general-relativistic notions of time.
Quantum Raychaudhuri equation

Saurya Das University of Lethbridge
February 20, 2014

PIRSA:14020130
General Relativity & Quantum Cosmology
We compute quantum corrections to the Raychaudhuri equation, by replacing classical geodesics with quantal (Bohmian) trajectories, and show that they prevent focusing of geodesics, and the formation of conjugate points. We discuss implications for the Hawking-Penrose singularity theorems, and for curvature singularities. Reference: arXiv: 1311.6539
Causality, holography, and entanglement entropy
February 20, 2014

PIRSA:14020146
General Relativity & Quantum Cosmology

High Energy Physics

Condensed Matter

General Relativity & Quantum Cosmology
After giving a brief overview of holographic entanglement entropy formulas, I will explore a curious feature they imply: when the bulk spacetime includes a black hole, the entanglement entropies often appear to depend on the spacetime geometry inside the horizon. I will ask whether this implies any loss of causality in the field theory. To answer this question, I will present a new general-relativity theorem concerning the causal structure of asymptotically AdS spacetimes, which implies an interesting relationship between bulk and boundary causal domains.
Non equilibrium thermodynamic of gravitational screens

Laurent Freidel Perimeter Institute for Theoretical Physics
February 19, 2014

PIRSA:14020144
General Relativity & Quantum Cosmology

Mathematical Physics
In this talk I will review the evidence for a mysterious and deep relationship between gravitational dynamics and thermodynamics. I will show how we can extend this connection to non equilibrium thermodynamics. Using the fact that the gravitational equations are fundamentally holographic, we express them in a way that shows a deep connection between gravity and the dynamics of viscous bubbles. We will explore some aspects of this surprising correspondence.
Firewall evasion by quantum gravity

Ted Jacobson University of Maryland, College Park
February 13, 2014

PIRSA:14020136
General Relativity & Quantum Cosmology
It has been argued that if black hole evaporation is a unitary quantum process, then a black hole horizon must be cloaked by a "firewall", i.e. a highly excited state of local quantum fields. This reasoning is based on factorizing the Hilbert space into interior and exterior degrees of freedom. Such factorization ignores the Wheeler-deWitt constraint equation, which arises from the diffeomorphism invariance of quantum gravity. I will argue that this constraint evades the firewall.
On null singularities in general relativity

Mihalis Dafermos Princeton University
February 13, 2014

PIRSA:14020133
General Relativity & Quantum Cosmology
This talk will discuss the formation, structure and interaction of null singularities for
the Einstein equations, as well as what this all means for the singular boundary
of generic space times within black hole regions.
The Radius of Neutron Stars and the Dense Matter Equation of State

Robert Rutledge McGill University
February 06, 2014

PIRSA:14020087
General Relativity & Quantum Cosmology
The equation of state of matter at and above nuclear densities remains a major theoretically uncertain prediction of QCD. Observations of the mass-radius relationship of neutron stars constrain, and can directly measure, the dense matter equation of state. I will discuss how measurements of neutron star radii have already constrained the dEOS, and how future work will directly measure the dEOS, providing an important constraint on models of the strong force.
Black hole entropy and the case for self-dual loop quantum gravity
January 29, 2014

PIRSA:14010098
General Relativity & Quantum Cosmology
By focusing on aspects of black hole thermodynamics, I will present some evidences supporting the unexpected role of the complex self-dual variables in quantum gravity. This will also be the occasion of revisiting some aspects of three-dimensional gravity, and in particular the link between the BTZ black hole and the Turaev-Viro state sum model. Also the information on the website for next week needs to be modified: We will not have a seminar on Thursday (as Thursday is PI day). Instead, we will have the seminar on Wednesday, but actually would prefer a different time, namely 3.30 pm.

Title	Speaker(s)	Date	Talk Type	Info link
Asymptotic Symmetries of Gauge and Gravity Theories in Minkowski Space	Andrew Strominger	2014-03-13	Scientific Series	View details
A one-dimensional action for simplicial gravity in three dimensions	Wolfgang Wieland	2014-03-06	Scientific Series	View details
Sequestering Lorentz violation in the Lifshitz sector	Maxim Pospelov	2014-03-06	Scientific Series	View details
Nonlocal cosmology	Richard Woodard	2014-02-27	Scientific Series	View details
À la recherche du temps perdu - Templeton Frontiers Colloquia	Flavio Mercati	2014-02-26	Scientific Series	View details
Quantum Raychaudhuri equation	Saurya Das	2014-02-20	Scientific Series	View details
Causality, holography, and entanglement entropy		2014-02-20	Scientific Series	View details
Non equilibrium thermodynamic of gravitational screens	Laurent Freidel	2014-02-19	Scientific Series	View details
Firewall evasion by quantum gravity	Ted Jacobson	2014-02-13	Scientific Series	View details
On null singularities in general relativity	Mihalis Dafermos	2014-02-13	Scientific Series	View details
The Radius of Neutron Stars and the Dense Matter Equation of State	Robert Rutledge	2014-02-06	Scientific Series	View details
Black hole entropy and the case for self-dual loop quantum gravity		2014-01-29	Scientific Series	View details

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General Relativity & Quantum Cosmology

Format results

Asymptotic Symmetries of Gauge and Gravity Theories in Minkowski Space

A one-dimensional action for simplicial gravity in three dimensions

Sequestering Lorentz violation in the Lifshitz sector

Nonlocal cosmology

À la recherche du temps perdu - Templeton Frontiers Colloquia

Quantum Raychaudhuri equation

Causality, holography, and entanglement entropy

Non equilibrium thermodynamic of gravitational screens

Firewall evasion by quantum gravity

On null singularities in general relativity

The Radius of Neutron Stars and the Dense Matter Equation of State

Black hole entropy and the case for self-dual loop quantum gravity

Asymptotic Symmetries of Gauge and Gravity Theories in Minkowski Space

A one-dimensional action for simplicial gravity in three dimensions

Sequestering Lorentz violation in the Lifshitz sector

Nonlocal cosmology

À la recherche du temps perdu - Templeton Frontiers Colloquia

Quantum Raychaudhuri equation

Causality, holography, and entanglement entropy

Non equilibrium thermodynamic of gravitational screens

Firewall evasion by quantum gravity

On null singularities in general relativity

The Radius of Neutron Stars and the Dense Matter Equation of State

Black hole entropy and the case for self-dual loop quantum gravity