General Relativity & Quantum Cosmology

Displaying 1489 - 1500 of 1878

What is motion? What is time?

Flavio Mercati University of Naples Federico II
January 23, 2013

PIRSA:13010003
General Relativity & Quantum Cosmology
The black hole information paradox and its resolution

Ted Jacobson University of Maryland, College Park
January 17, 2013

PIRSA:13010021
General Relativity & Quantum Cosmology
New transport properties of holographic superfluids

Daniel Fernandez University of Iceland
January 10, 2013

PIRSA:13010004
General Relativity & Quantum Cosmology
Black holes: To be or not be, that is the question

Luis Garay Complutense University of Madrid
December 13, 2012

PIRSA:12120032
General Relativity & Quantum Cosmology
Renormalizing TGFTs: a 3d example on SU(2)

Sylvain Carrozza University of Burgundy
December 06, 2012

PIRSA:12120007
General Relativity & Quantum Cosmology
Approaches to modeling pulsar magnetospheres

Anatoly Spitkovsky Princeton University
December 06, 2012

PIRSA:12120001
General Relativity & Quantum Cosmology
Mass and Tension (momentum) Sum Rules in AdS (dS)

Jennie Traschen University of Massachusetts Amherst
November 27, 2012

PIRSA:12110042
General Relativity & Quantum Cosmology
Dynamical Capture Compact Binary Mergers

William East Perimeter Institute for Theoretical Physics
November 22, 2012

PIRSA:12110054
General Relativity & Quantum Cosmology
Canonical tensor models with local time

Naoki Sasakura Yukawa Institute for Theoretical Physics
November 15, 2012

PIRSA:12110065
General Relativity & Quantum Cosmology
Detecting Gravitational Waves with Millisecond Pulsars

Paul Demorest National Radio Astronomy Observatory (NRAO)
November 15, 2012

PIRSA:12110044
General Relativity & Quantum Cosmology
Dynamical evaporation of quantum horizons
November 08, 2012

PIRSA:12110064
General Relativity & Quantum Cosmology
Effective field theory framework in QG
- Xavier Calmet University of Sussex
- Roberto Percacci SISSA International School for Advanced Studies
- Astrid Eichhorn Universität Heidelberg
- Martin Reuter Johannes Gutenberg University Mainz
October 25, 2012

PIRSA:12100121
General Relativity & Quantum Cosmology

What is motion? What is time?

Flavio Mercati University of Naples Federico II
January 23, 2013

PIRSA:13010003
General Relativity & Quantum Cosmology
I give an account of the Machian approach to dynamics, from Mach's critique of Newton to the work of Barbour, Bertotti, York and O'Murchadha, which culminated in the theory of Shape Dynamics, a new and original way of thinking about General Relativity. I conclude commenting on the present research lines in Shape Dynamics, and the opportunity it offers to solve the problem of time in quantum gravity.

Support for this colloquium is provided by The Templeton Frontiers Program.
The black hole information paradox and its resolution

Ted Jacobson University of Maryland, College Park
January 17, 2013

PIRSA:13010021
General Relativity & Quantum Cosmology
Both AdS/CFT duality and more general reasoning from quantum gravity point to a rich collection of boundary observables that always evolve unitarily. The physical quantum gravity states described by these observables must be solutions of the spatial diffeomorphism and Wheeler-deWitt constraints, which implies that the state space does not factorize into a tensor product of localized degrees of freedom. The "firewall" argument that unitarity of black hole evaporation is incompatible with a regular near horizon region is based on such a factorization, hence is not applicable in quantum gravity. A version of black hole complementarity resolves the apparent conflict. (I will also discuss doubts and questions.)
New transport properties of holographic superfluids

Daniel Fernandez University of Iceland
January 10, 2013

PIRSA:13010004
General Relativity & Quantum Cosmology
In the context of holography applied to condensed matter theory, I will present an analysis of transport properties of p-wave superfluids by means of a gravity dual. Fluctuations modes in the SU(2) Einstein-Yang-Mills theory are considered, and phenomenological implications are derived. Due to the spatial anisotropy of the system, a non-universal shear viscosity is obtained, along with a new coefficient associated to normal stress differences. I will also discuss how the transport phenomena in this model is related to the thermoelectric, flexoelectric and piezoelectric effects (mixing of electric current, heat flux and mechanical stress), which have been observed in some superconductors and crystal liquids.
Black holes: To be or not be, that is the question

Luis Garay Complutense University of Madrid
December 13, 2012

PIRSA:12120032
General Relativity & Quantum Cosmology
I will review some problems of the black hole paradigm and explore other
possibilities for the final state of stellar collapse other than an evaporating
black hole. In particular I will use the so-called transplanckian problem as a
guide in this search for a compelling scenario for the evaporation of
ultracompact objects.
Renormalizing TGFTs: a 3d example on SU(2)

Sylvain Carrozza University of Burgundy
December 06, 2012

PIRSA:12120007
General Relativity & Quantum Cosmology
I will recall the main motivations for considering spin foam models in their Group Field Theory (GFT) versions, which are quantum field theories defined on group manifolds. As for any other quantum field theory, a fully consistent definition of the latter must involve renormalization. I will briefly review a specific class of GFTs, called tensorial, for which progress in this direction has recently been possible. A new just-renormalizable model, in three dimensions and on the SU(2) group, will be presented. Interestingly, it includes the geometric constraint of the Boulatov model, and might as such be related to Euclidean quantum gravity in three dimensions. Furthermore, this opens the way to a similar analysis of current 4d gravity spin foam models.
Approaches to modeling pulsar magnetospheres

Anatoly Spitkovsky Princeton University
December 06, 2012

PIRSA:12120001
General Relativity & Quantum Cosmology
Pulsars are rotating magnetized neutron stars that emit broadband pulses of radiation. Our ability to model magnetospheres of pulsars has been hampered by the difficulty of solving the self-consistent behavior of strongly magnetized relativistic plasmas. I will describe
recent progress in numerical modeling of magnetically-dominated plasmas and show applications to pulsar magnetospheres in increasing levels of realism, including ideal and resistive force-free,
relativistic MHD and kinetic models. The knowledge of the magnetospheric shape together with the new observations of gamma-ray emission from pulsars with Fermi telescope allow to directly constrain the location and physics of the acceleration regions in the magnetosphere and the origin of high energy emission. The pulsar magnetosphere is a prototype for other strongly magnetized
astrophysical objects, and I will discuss how the lessons from pulsar modeling can be useful in predicting EM counterparts to gravitational wave sources.
Mass and Tension (momentum) Sum Rules in AdS (dS)

Jennie Traschen University of Massachusetts Amherst
November 27, 2012

PIRSA:12110042
General Relativity & Quantum Cosmology
The stress-energy tensor in a conformal field theory has zero trace. Hence AdS boundary stress-tensors are traceless by construction, to match this property of the dual CFT. An elegant (aka nifty) construction based on the conformal isometry of AdS will be presented which shows that in an asymptotically AdS spacetime, the sum of the ADM mass and the ADM tensions is zero. This result follows strictly from the gravitational point of view- that is, the Einstein equations and the definitions of the ADM charges. Further, it turns out that perturbative stress-energy sources in an asymptotically AdS spacetime must satisfy a local version of this constraint, namely that the sum of the energy density minus the pressures equals zero. The situation with positive cosmological constant is both similar and distinct in interesting ways, which will be briefly discussed. The analogous (analytically continued) conformal isometry in dS is the root of the ``k^4 “ power spectrum for causal cosmological perturbations. Work in progress (speculations) will be presented about a corresponding sum-rule for gravitational charges defined at future infinity in a spacetime that approaches dS at late times.
Dynamical Capture Compact Binary Mergers

William East Perimeter Institute for Theoretical Physics
November 22, 2012

PIRSA:12110054
General Relativity & Quantum Cosmology
Canonical tensor models with local time

Naoki Sasakura Yukawa Institute for Theoretical Physics
November 15, 2012

PIRSA:12110065
General Relativity & Quantum Cosmology
Tensor models are generalization of matrix models, and are studied as discrete models for quantum gravity for more than two-dimensions. Among them, the rank-three tensor models can be interpreted as theories of dynamical fuzzy spaces, and they generally have the feature of
respecting symmetries. In this talk, after briefly reviewing some results on Euclidean models such as spontaneous generation of fuzzy spaces and Euclidean general relativity respecting the diffeomorphism symmetry on them, I will present a way to introduce “local” time to the rank-three tensor models by constructing “local” Hamiltonians. The consistency among the multiple ways of local time evolutions is guaranteed by the on-shell closure of the constraint algebra among the
local Hamiltonians and the symmetry generators of the tensor models. The constraint algebra is shown to approach the DeWitt algebra in a formal continuum limit. I will also discuss the two-fold uniqueness of the local Hamiltonians, and will briefly show some preliminary results on the quantization.
Detecting Gravitational Waves with Millisecond Pulsars

Paul Demorest National Radio Astronomy Observatory (NRAO)
November 15, 2012

PIRSA:12110044
General Relativity & Quantum Cosmology
Millisecond spin-period radio pulsars provide us with unique astronomical "laboratories" for exploring fundamental physics in a variety of ways -- from the physics of matter at super-nuclear density, to experimental tests of gravity. They have also provided the only experimental evidence so far for the existence of gravitational waves (GW). A set of millisecond pulsars acting as precise astronomical clocks may also be used as a direct GW detector, sensitive to the nanohertz-frequency GW expected to be emitted by supermassive black hole binary systems or other more exotic sources. In this talk I will present the project status and recent GW upper limits from the NANOGrav project. I will also discuss expected near-future improvements in the measurement, including recent work aimed at better characterizing and mitigating the effect of multi-path propagation effects in the interstellar medium.
Dynamical evaporation of quantum horizons
November 08, 2012

PIRSA:12110064
General Relativity & Quantum Cosmology
We describe of the evaporation process as driven by the dynamical evolution of the quantum gravitational degrees of freedom resident at the horizon, as identified by the Loop Quantum Gravity kinematics. Using a parallel with the Brownian motion, we interpret the first law of quantum dynamical horizon in terms of a fluctuation-dissipation relation applied to this fundamental discrete structure. In this way, the horizon evolution is described in terms of relaxation to an equilibrium state balanced by the excitation of Planck scale constituents of the horizon. We show how from this setting the emergence of several conservative scenarios for the final stage of the evaporation process can be microscopically derived. Namely, the leakage of part of the horizon quantum geometry information prior to the Planckian phase and the stabilization of the hole surface shrinkage forming a massive remnant, which can eventually decay, are shown to take place.
Effective field theory framework in QG
- Xavier Calmet University of Sussex
- Roberto Percacci SISSA International School for Advanced Studies
- Astrid Eichhorn Universität Heidelberg
- Martin Reuter Johannes Gutenberg University Mainz
October 25, 2012

PIRSA:12100121
General Relativity & Quantum Cosmology
Gravity Induced Grand Unification
Motivated by the lack of evidence for physics beyond the Standard Model in the TeV region, we discussed an alternative path for grand unification. We show that simple grand unification models based on e.g. SU(5) can work successfully even without low scale supersymmetry. In particular quantum gravitational effects could easily modify the unification conditions for the gauge and Yukawa couplings.
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Testing the consistency of quantum gravity with low-energy properties of the standard model
Testing quantum gravity is possible by using, e.g. the available data on the properties of the standard model. I will discuss how a parameterisation of quantum gravity fluctuations in terms of metric fluctuations can be used to test the compatibility of quantum gravity with the observed low-energy properties of the standard model, such as the existence of fermions with masses much below the Planck mass.
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The Asymptotic Safety program
The effective average action approach to Quantum Einstein Gravity (QEG) is discussed as a natural framework for exploring the scale dependent Riemannian geometry and multifractal micro-structure of the effective spacetimes predicted by QEG. Their fractal properties are related to the functional RG flow on theory space, and the special role of the running cosmological constant is emphasized. The prospects of an experimental verification will also be discussed.

Title	Speaker(s)	Date	Talk Type	Info link
What is motion? What is time?	Flavio Mercati	2013-01-23	Scientific Series	View details
The black hole information paradox and its resolution	Ted Jacobson	2013-01-17	Scientific Series	View details
New transport properties of holographic superfluids	Daniel Fernandez	2013-01-10	Scientific Series	View details
Black holes: To be or not be, that is the question	Luis Garay	2012-12-13	Scientific Series	View details
Renormalizing TGFTs: a 3d example on SU(2)	Sylvain Carrozza	2012-12-06	Scientific Series	View details
Approaches to modeling pulsar magnetospheres	Anatoly Spitkovsky	2012-12-06	Scientific Series	View details
Mass and Tension (momentum) Sum Rules in AdS (dS)	Jennie Traschen	2012-11-27	Scientific Series	View details
Dynamical Capture Compact Binary Mergers	William East	2012-11-22	Scientific Series	View details
Canonical tensor models with local time	Naoki Sasakura	2012-11-15	Scientific Series	View details
Detecting Gravitational Waves with Millisecond Pulsars	Paul Demorest	2012-11-15	Scientific Series	View details
Dynamical evaporation of quantum horizons		2012-11-08	Scientific Series	View details
Effective field theory framework in QG	Xavier Calmet, Roberto Percacci, Astrid Eichhorn, Martin Reuter	2012-10-25	Conference	View details

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General Relativity & Quantum Cosmology

Format results

What is motion? What is time?

The black hole information paradox and its resolution

New transport properties of holographic superfluids

Black holes: To be or not be, that is the question

Renormalizing TGFTs: a 3d example on SU(2)

Approaches to modeling pulsar magnetospheres

Mass and Tension (momentum) Sum Rules in AdS (dS)

Dynamical Capture Compact Binary Mergers

Canonical tensor models with local time

Detecting Gravitational Waves with Millisecond Pulsars

Dynamical evaporation of quantum horizons

Effective field theory framework in QG

What is motion? What is time?

The black hole information paradox and its resolution

New transport properties of holographic superfluids

Black holes: To be or not be, that is the question

Renormalizing TGFTs: a 3d example on SU(2)

Approaches to modeling pulsar magnetospheres

Mass and Tension (momentum) Sum Rules in AdS (dS)

Dynamical Capture Compact Binary Mergers

Canonical tensor models with local time

Detecting Gravitational Waves with Millisecond Pulsars

Dynamical evaporation of quantum horizons

Effective field theory framework in QG