Strong Gravity

312 talks

S020

Collection TypeSeries

SubjectGeneral Relativity & Quantum Cosmology

Source RepositoryPIRSA

Displaying 253 - 264 of 312

Particle Acceleration by Magnetic Reconnection in Striped Pulsar Winds and Relativistic Jets

Lorenzo Sironi Columbia University
March 21, 2013

PIRSA:13030078
General Relativity & Quantum Cosmology
The dynamics of asymptotically anti-de Sitter spacetimes

Claude Warnick
March 14, 2013

PIRSA:13030077
General Relativity & Quantum Cosmology
Exploiting the Strong Gravitational Fields of Neutron Stars to Measure their Properties

Dimitrios Psaltis University of Arizona
February 28, 2013

PIRSA:13020126
General Relativity & Quantum Cosmology
Gamma Rays at 130 GeV and How They Might Come from Dark Matter

Andrew Frey University of Winnipeg
February 21, 2013

PIRSA:13020139
Astrophysics

General Relativity & Quantum Cosmology
New transport properties of holographic superfluids

Daniel Fernandez University of Iceland
January 10, 2013

PIRSA:13010004
General Relativity & Quantum Cosmology
Approaches to modeling pulsar magnetospheres

Anatoly Spitkovsky Princeton University
December 06, 2012

PIRSA:12120001
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
Detecting Gravitational Waves with Millisecond Pulsars

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

PIRSA:12110044
General Relativity & Quantum Cosmology
Penrose inequalities and the stability of non-uniform black strings

Pau Figueras Queen Mary University of London

November 01, 2012

PIRSA:12110039
Towards an Asymptotically AdS Description of Heavy Ion Collisions

Hans Bantilan Princeton University
October 18, 2012

PIRSA:12100076
High Energy Physics
Testing Strong-Field General Relativity with Black Holes

Tim Johannsen

October 04, 2012

PIRSA:12100049
Critical Collapse in the Axion-Dilaton System in Diverse Dimensions

Ehsan Hatefi The Abdus Salam International Centre for Theoretical Physics (ICTP)
August 30, 2012

PIRSA:12080044
High Energy Physics

Particle Acceleration by Magnetic Reconnection in Striped Pulsar Winds and Relativistic Jets

Lorenzo Sironi Columbia University
March 21, 2013

PIRSA:13030078
General Relativity & Quantum Cosmology
The relativistic wind of pulsars consists of toroidal stripes of opposite magnetic field polarity, separated by current sheets of hot plasma. By means of 2D and 3D particle-in-cell simulations, we investigate particle acceleration and magnetic field dissipation at the termination shock of a striped pulsar wind. At the shock, the flow compresses and the alternating fields annihilate by driven magnetic reconnection. Irrespective of the stripe wavelength "lambda" or the wind magnetization "sigma" (in the regime sigma>>1 of magnetically-dominated flows), shock-driven reconnection transfers all the magnetic energy of the alternating fields to the particles. As the value of lambda/(r_L*sigma) increases (here, r_L is the relativistic Larmor radius in the wind), the post-shock spectrum passes from a thermal Maxwellian to a flat power-law tail with slope around -1.5, populated by particles accelerated by the reconnection electric field. The limit lambda/(r_L*sigma)>>1 is realized in relativistic jets, where kink instabilities may seed the conditions for magnetic reconnection. Here, we find that the particle spectrum in the current sheet approaches a flat power-law tail with slope between -1.5 and -2, regardless of the conditions in the jet. The spectrum extends to higher energies for larger magnetizations or colder plasma temperatures, everything else being fixed. Our results place important constraints on the emission models of Pulsar Wind Nebulae and magnetically-dominated astrophysical jets.
The dynamics of asymptotically anti-de Sitter spacetimes

Claude Warnick
March 14, 2013

PIRSA:13030077
General Relativity & Quantum Cosmology
The majority of work on asymptotically anti-de Sitter spacetimes, much of it motivated by the AdS/CFT correspondence, assumes configurations which are either at or close to equilibrium. Recently it has been discovered that genuinely dynamical spacetimes with AdS asymptotics can exhibit some surprising behaviour. In particular, numerical studies suggest AdS is dynamically unstable. I will discuss recent analytical (in)stability results for asymptotically AdS spacetimes, in particular how stability can be affected by boundary conditions at the timelike conformal infinity.
Exploiting the Strong Gravitational Fields of Neutron Stars to Measure their Properties

Dimitrios Psaltis University of Arizona
February 28, 2013

PIRSA:13020126
General Relativity & Quantum Cosmology
Neutron stars possess the strongest gravitational fields among stellar objects in the Universe that are not surrounded by a horizon. This causes the emission from their surfaces to be strongly lensed and deformed. Two upcoming space X-ray missions, ESA's LOFT and NASA's NICER, aim to use observations of lightcurves from spinning neutron stars to map their gravitational fields as well as measure their masses and radii. In this talk, I will discuss some unexpected strong-field phenomena that affect gravitational lensing in the vicinity of neutron stars. I will then show how we can use these phenomena to measure strong-field frame dragging and break degeneracies in the measured neutron-star masses and radii.
Gamma Rays at 130 GeV and How They Might Come from Dark Matter

Andrew Frey University of Winnipeg
February 21, 2013

PIRSA:13020139
Astrophysics

General Relativity & Quantum Cosmology
Gamma Rays at 130 GeV and How They Might Come from Dark Matter" I'll discuss the exciting (but somewhat controversial) new discovery of a sharp gamma ray feature at 130 GeV from near the galactic center and review some other evidence that might link it to annihilation of dark matter. I will then explain the challenges in understanding how dark matter might produce this signal and explain a model or two that overcome these difficulties.
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.
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.
Dynamical Capture Compact Binary Mergers

William East Perimeter Institute for Theoretical Physics
November 22, 2012

PIRSA:12110054
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
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.
Penrose inequalities and the stability of non-uniform black strings

Pau Figueras Queen Mary University of London

November 01, 2012

PIRSA:12110039

In this talk I will first review static black holes in Kaluza-Klein theory. It is well-known that within this theory there exist black strings which are non-uniform along the Kaluza-Klein circle. Using numerical methods, I will explain how to construct (for the first time) non-uniform black strings in D>10, where D is the total number of spacetime dimensions. The stability of such black objects has not been discussed before, and in the last part of the talk I will explain how one can study the stability of non-uniform black strings using Penrose inequalities. This will lead to a new conjecture for the phase diagram of static Kaluza-Klein black holes.
Towards an Asymptotically AdS Description of Heavy Ion Collisions

Hans Bantilan Princeton University
October 18, 2012

PIRSA:12100076
High Energy Physics
I will discuss recent work in simulating asymptotically anti-de Sitter spacetimes, and its relation to heavy ion collider physics. For this purpose, I intend to focus on a class of oblately deformed black hole spacetime solutions. For each of these solutions, I will map the gravitational metric in the spacetime bulk to a stress tensor one-point function of the conformal field theory defined on the spacetime boundary. During the ring-down process, wherein the deformed black hole settles down to the AdS analog of the Schwarzschild solution, I will exhibit evidence that the dual CFT stress tensor on the boundary is that of an N=4 SYM fluid, even for black holes of significant deformation well outside the perturbative regime. We will conformally map the boundary fluid onto a real-world fluid in Minkowski space, and discover a temperature profile which can be thought of as approximating that of a head-on heavy ion collision at its moment of impact. I will close with a description of recent parallel explorations.
Testing Strong-Field General Relativity with Black Holes

Tim Johannsen

October 04, 2012

PIRSA:12100049
Critical Collapse in the Axion-Dilaton System in Diverse Dimensions

Ehsan Hatefi The Abdus Salam International Centre for Theoretical Physics (ICTP)
August 30, 2012

PIRSA:12080044
High Energy Physics
We study the gravitational collapse of the axion-dilaton system suggested by type IIB string theory in dimensions ranging from four to ten. We extend previous analysis concerning the role played by the global SL(2, R) symmetry and also we explain ,why we do have three different assumptions(cases). We evaluate the Choptuik exponents in the elliptic case. Eventually we try to explain some of the open questions for two other assumptions and future directions.

Title	Speaker(s)	Date	Talk Type	Info
Particle Acceleration by Magnetic Reconnection in Striped Pulsar Winds and Relativistic Jets	Lorenzo Sironi	2013-03-21	Scientific Series	View details
The dynamics of asymptotically anti-de Sitter spacetimes	Claude Warnick	2013-03-14	Scientific Series	View details
Exploiting the Strong Gravitational Fields of Neutron Stars to Measure their Properties	Dimitrios Psaltis	2013-02-28	Scientific Series	View details
Gamma Rays at 130 GeV and How They Might Come from Dark Matter	Andrew Frey	2013-02-21	Scientific Series	View details
New transport properties of holographic superfluids	Daniel Fernandez	2013-01-10	Scientific Series	View details
Approaches to modeling pulsar magnetospheres	Anatoly Spitkovsky	2012-12-06	Scientific Series	View details
Dynamical Capture Compact Binary Mergers	William East	2012-11-22	Scientific Series	View details
Detecting Gravitational Waves with Millisecond Pulsars	Paul Demorest	2012-11-15	Scientific Series	View details
Penrose inequalities and the stability of non-uniform black strings	Pau Figueras	2012-11-01	Scientific Series	View details
Towards an Asymptotically AdS Description of Heavy Ion Collisions	Hans Bantilan	2012-10-18	Scientific Series	View details
Testing Strong-Field General Relativity with Black Holes	Tim Johannsen	2012-10-04	Scientific Series	View details
Critical Collapse in the Axion-Dilaton System in Diverse Dimensions	Ehsan Hatefi	2012-08-30	Scientific Series	View details

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Format results

Particle Acceleration by Magnetic Reconnection in Striped Pulsar Winds and Relativistic Jets

The dynamics of asymptotically anti-de Sitter spacetimes

Exploiting the Strong Gravitational Fields of Neutron Stars to Measure their Properties

Gamma Rays at 130 GeV and How They Might Come from Dark Matter

New transport properties of holographic superfluids

Approaches to modeling pulsar magnetospheres

Dynamical Capture Compact Binary Mergers

Detecting Gravitational Waves with Millisecond Pulsars

Penrose inequalities and the stability of non-uniform black strings

Towards an Asymptotically AdS Description of Heavy Ion Collisions

Testing Strong-Field General Relativity with Black Holes

Critical Collapse in the Axion-Dilaton System in Diverse Dimensions

Particle Acceleration by Magnetic Reconnection in Striped Pulsar Winds and Relativistic Jets

The dynamics of asymptotically anti-de Sitter spacetimes

Exploiting the Strong Gravitational Fields of Neutron Stars to Measure their Properties

Gamma Rays at 130 GeV and How They Might Come from Dark Matter

New transport properties of holographic superfluids

Approaches to modeling pulsar magnetospheres

Dynamical Capture Compact Binary Mergers

Detecting Gravitational Waves with Millisecond Pulsars

Penrose inequalities and the stability of non-uniform black strings

Towards an Asymptotically AdS Description of Heavy Ion Collisions

Testing Strong-Field General Relativity with Black Holes

Critical Collapse in the Axion-Dilaton System in Diverse Dimensions