General Relativity & Quantum Cosmology

Displaying 1405 - 1416 of 1878

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
Wilson Lines in Higher Spin Gravity

Alejandra Castro University of Cambridge
January 23, 2014

PIRSA:14010081
General Relativity & Quantum Cosmology
Curvature in terms of entanglement

Achim Kempf University of Waterloo
December 12, 2013

PIRSA:13120064
General Relativity & Quantum Cosmology
From spin foams to anyons and back again - Joint Condensed Matter/Quantum Gravity Seminar

Bianca Dittrich Perimeter Institute for Theoretical Physics
December 05, 2013

PIRSA:13120048
General Relativity & Quantum Cosmology
Divergences in Spinfoam Quantum Gravity

Aldo Riello Perimeter Institute for Theoretical Physics
November 28, 2013

PIRSA:13110063
General Relativity & Quantum Cosmology
Collisions in AdS and the thermalisation of heavy-ion collisions

Wilke van der Schee European Organization for Nuclear Research (CERN)
November 28, 2013

PIRSA:13110089
General Relativity & Quantum Cosmology
Dimensional reduction in the sky
November 21, 2013

PIRSA:13110059
General Relativity & Quantum Cosmology
Charged particle motion in magnetized black holes

Valeri Frolov University of Alberta
November 21, 2013

PIRSA:13110066
General Relativity & Quantum Cosmology
Finite regions, spherical entanglement, and quantum gravity

Hal Haggard Bard College
November 14, 2013

PIRSA:13110049
General Relativity & Quantum Cosmology
Self-force and Green function in Schwarzschild spacetime via quasinormal modes and branch cut

Marc Casals Universität Leipzig
November 14, 2013

PIRSA:13110067
General Relativity & Quantum Cosmology
Matter matters in asymptotically safe quantum gravity
November 07, 2013

PIRSA:13110048
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
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.
Wilson Lines in Higher Spin Gravity

Alejandra Castro University of Cambridge
January 23, 2014

PIRSA:14010081
General Relativity & Quantum Cosmology
In this talk I will review the interpretation of Wilson line operators in the context of higher spin gravity in 2+1 dim and holography. I will show how a Wilson line encapsulates the thermodynamics of black holes. Furthermore it provides an elegant description of massive particles. This opens a new window of observables which will allow us to probe the true geometrical nature of higher spin gravity.
Curvature in terms of entanglement

Achim Kempf University of Waterloo
December 12, 2013

PIRSA:13120064
General Relativity & Quantum Cosmology
The entanglement of the quantum field theoretic vacuum state is affected by curvature. I ask if or under which conditions the curvature of spacetime can be expressed entirely in terms of the spatial entanglement structure of the vacuum. This would open up the prospect that general relativity could be formulated in quantum theoretic terms, which should then be helpful for studies in quantum gravity.
From spin foams to anyons and back again - Joint Condensed Matter/Quantum Gravity Seminar

Bianca Dittrich Perimeter Institute for Theoretical Physics
December 05, 2013

PIRSA:13120048
General Relativity & Quantum Cosmology
Spin foams provide models for quantum gravity and hence quantum space time. One of the key outstanding questions is to show that they reproduce smooth space time manifolds in a continuum limit.I will start with a very short introduction to spin foams and the structure of quantum space time they encode. I will explain how the investigation of the continuum limit via coarse graining and renormalization techniques led as to consider anyonic spin chains and a classification of ground states in systems with quantum group symmetries.I will then present new results on the continuum limit of spin net models, that allow us to draw first conclusions about the large scale dynamics of spin foams.
Based on: B.D., W. Kaminski, Topological lattice field theories from intertwiner dynamics, arXiv:1311.1798, B.D., S. Steinhaus, Time evolution as refining, coarse graining and entangling, to appear, B.D. M. Martin-Benito, S. Steinhaus, The refinement limit of quantum group spin net models, to appear
Divergences in Spinfoam Quantum Gravity

Aldo Riello Perimeter Institute for Theoretical Physics
November 28, 2013

PIRSA:13110063
General Relativity & Quantum Cosmology
The most relevant evidences in favour of the Lorentzian EPRL-FK spinfoam model come from its capibility of reproducing the expected semiclassical limit in the large spin regime. The main examples of this are the large spin limit of the vertex amplitude, later extended to arbitrary triangulations, and that of the spinfoam graviton propagator, which was calculated on the simplest possible two complex. These results are very promising. Nonetheless, their relevance may be endangered by the effects associated to radiative corrections. In this seminar, I will focus on the role played by the simplest diverging graph, the so called 'melon graph', which is known to play a fundamental role in tensorial group field theories. In particular, I will discuss its most divergent part and its geometrical interpretation. I will finally comment on the result, with particular attention to its physical consequences, especially in relation with the semiclassical limit of the spinfoam graviton propagator.
Collisions in AdS and the thermalisation of heavy-ion collisions

Wilke van der Schee European Organization for Nuclear Research (CERN)
November 28, 2013

PIRSA:13110089
General Relativity & Quantum Cosmology
The motivation of this seminar is to understand the thermalisation of heavy ion collisions using AdS/CFT. These collisions can be modelled as colliding planar gravitational shock waves. This gives rise to rich and interesting dynamics; wide shocks come to a full stop and expand hydrodynamically, as was previously found by Chesler and Yaffe. High energy collisions (corresponding to thin shocks) pass through each other, after which a plasma forms in the middle, within a proper time 1/T, with T the local temperature at that time. After this I will discuss recent results where we studied the influence of microscopic structure in the longitudinal direction of the shock waves, and thereby found a coherent regime. This has implications for both fluctuations in nucleus-nucleus collisions, and for recent proton-lead collisions at at LHC. The final part will cover a radially expanding calculation, where some simplifications allowed us to solve the model all the way till the final particle spectra, with an interesting comparison with experimental data.
Dimensional reduction in the sky
November 21, 2013

PIRSA:13110059
General Relativity & Quantum Cosmology
In several approaches to quantum-gravity, the spectral dimension of spacetime runs from the standard value of 4 in the infrared (IR) to a smaller value in the ultraviolet (UV). Describing this running in terms of deformed dispersion relations, I show that a striking cosmological implication is that that UV behavior leading to 2 spectral dimensions results in an exactly scale-invariant spectrum of vacuum scalar and tensor fluctuations. I discuss scenarios that break exact scale-invariance and show that the tensor to scalar ratio is fixed by the UV ratio between the speed of gravity and the speed of light. Cosmological perturbations in this framework display a wavelength-dependent speed of light, but by transforming to a suitable "rainbow frame" this feature can be removed, at the expense of modifying gravity. In particular it turns out that the following concepts are closely connected: scale-invariance of vacuum fluctuations, conformal invariance of the gravitational coupling, UV reduction to spectral dimension 2 in position space and UV reduction to Hausdorff dimension 2 in energy-momentum space.
Charged particle motion in magnetized black holes

Valeri Frolov University of Alberta
November 21, 2013

PIRSA:13110066
General Relativity & Quantum Cosmology
There exist evidences that magnetic field in the vicinity of astrophysical black holes plays an important role. In particular it is required for explanation of such phenomenon as jet formation. Study of such problems in all their complexity requires 3D numerical simulations of the magnetohydrodynamics in a strong gravitational field. Quite often when dealing with such a complicated problem it is instructive to consider first its simplifications, which can be treated either analytically, or by integrating ordinary differential equations. Motion of a charged particle in a weakly magnetized black hole is an important example. We consider a non-rotating black hole in the weak magnetic field which is homogeneous at infinity. In the talk I discuss the following problems: How does such a magnetic field affect charged particle motion in the equatorial plane? How does it change the radius of the innermost stable circular orbits (ISCO) and period of rotation? I shall demonstratethat the magnetic field increases the efficiency of the energy extraction from the black hole and that magnetized black holes can be used as "particle accelerators". Finally, I shall discuss out-of-equatorial-plane motion and demonstrate that it is chaotic. Possible applications of these results to astrophysics are briefly discussed.
Finite regions, spherical entanglement, and quantum gravity

Hal Haggard Bard College
November 14, 2013

PIRSA:13110049
General Relativity & Quantum Cosmology
An exciting frontier in physics is to understand the quantum nature of gravitation in finite regions of spacetime. Study of these regions from ``below'', that is, by studying the quantum geometry of finite regions emerging from loop gravity and spin networks has recently resulted in a new road to the quantization of volume and to evidence that there is a robust gap in the volume spectrum. In this talk I will complement these results with recent work on conformal field theories in a particular finite region, a spherical ball of space. This new view afforded from ``above" gives insights into entanglement and the Reeh-Schlieder theorem, allows calculation of the entanglement spectrum, and suggests a new route to constructing the Minkowski vacuum out of independent finite regions in quantum gravity.
Self-force and Green function in Schwarzschild spacetime via quasinormal modes and branch cut

Marc Casals Universität Leipzig
November 14, 2013

PIRSA:13110067
General Relativity & Quantum Cosmology
The modelling of gravitational wave sources is of timely interest given the exciting prospect of a first detection of gravitational waves by the new generation of detectors. The motion of a small compact object around a massive black hole deviates from a geodesic due to the action of its own field, giving rise to a self-force and the emission of gravitational waves. The self-force program has recently achieved important results using well-established methods. In this talk, we will present a different, novel method, where the self-force is calculated via the Green function of the wave equation that the field perturbation satisfies. We will present a calculation of the global Green function on Schwarzschild black hole spacetime. The calculation is carried out via a spectroscopy analysis of the Green function, which includes quasinormal modes and a branch cut in the complex-frequency plane. We will apply this analysis to calculate the self-force on a scalar charge and to reveal geometrical properties of wave propagation on a Schwarzschild background.
Matter matters in asymptotically safe quantum gravity
November 07, 2013

PIRSA:13110048
General Relativity & Quantum Cosmology
The Functional Renormalisation Group technique has received great attention in recent times proving itself as a powerful tool to describe the high energy behaviour of gravitational interactions.
Its key ingredient is a nontrivial fixed point of the theory renormalization group flow which controls the behavior of the coupling constants in the ultraviolet regime and ensures that physical quantities are safe from divergences. I will briefly review the main ingredients of the gravitational asymptotic safety framework before focusing on the effect of massless minimally coupled scalars, fermions and vector fields on the gravitational fixed point. I will then set bounds on the type and number of such fields requiring the existence of a UV attractive fixed point. I will also discuss the dynamically generated quantum-gravity scale in asymptotic safety, which is the transition scale to the fixed-point regime, and its variation as a function of matter degrees of freedom. To conclude I will also consider the case of higher dimensional models.

Title	Speaker(s)	Date	Talk Type	Info link
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
Wilson Lines in Higher Spin Gravity	Alejandra Castro	2014-01-23	Scientific Series	View details
Curvature in terms of entanglement	Achim Kempf	2013-12-12	Scientific Series	View details
From spin foams to anyons and back again - Joint Condensed Matter/Quantum Gravity Seminar	Bianca Dittrich	2013-12-05	Scientific Series	View details
Divergences in Spinfoam Quantum Gravity	Aldo Riello	2013-11-28	Scientific Series	View details
Collisions in AdS and the thermalisation of heavy-ion collisions	Wilke van der Schee	2013-11-28	Scientific Series	View details
Dimensional reduction in the sky		2013-11-21	Scientific Series	View details
Charged particle motion in magnetized black holes	Valeri Frolov	2013-11-21	Scientific Series	View details
Finite regions, spherical entanglement, and quantum gravity	Hal Haggard	2013-11-14	Scientific Series	View details
Self-force and Green function in Schwarzschild spacetime via quasinormal modes and branch cut	Marc Casals	2013-11-14	Scientific Series	View details
Matter matters in asymptotically safe quantum gravity		2013-11-07	Scientific Series	View details

Supported by

General Relativity & Quantum Cosmology

Format results

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

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

Wilson Lines in Higher Spin Gravity

Curvature in terms of entanglement

From spin foams to anyons and back again - Joint Condensed Matter/Quantum Gravity Seminar

Divergences in Spinfoam Quantum Gravity

Collisions in AdS and the thermalisation of heavy-ion collisions

Dimensional reduction in the sky

Charged particle motion in magnetized black holes

Finite regions, spherical entanglement, and quantum gravity

Self-force and Green function in Schwarzschild spacetime via quasinormal modes and branch cut

Matter matters in asymptotically safe quantum gravity

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

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

Wilson Lines in Higher Spin Gravity

Curvature in terms of entanglement

From spin foams to anyons and back again - Joint Condensed Matter/Quantum Gravity Seminar

Divergences in Spinfoam Quantum Gravity

Collisions in AdS and the thermalisation of heavy-ion collisions

Dimensional reduction in the sky

Charged particle motion in magnetized black holes

Finite regions, spherical entanglement, and quantum gravity

Self-force and Green function in Schwarzschild spacetime via quasinormal modes and branch cut

Matter matters in asymptotically safe quantum gravity