Strong Gravity

318 talks

S020

Collection TypeSeries

Displaying 253 - 264 of 318

Detectable signatures of compact binaries involving neutron stars

Vasileios Paschalidis University of Illinois Urbana-Champaign
May 16, 2013

PIRSA:13050075
Strong Gravity
David Defeats Goliath: How Ultralight Fields Affect The Dynamics of Massive Black Holes

Paolo Pani Instituto Superior Tecnico - Departamento de Física
May 09, 2013

PIRSA:13050001
Strong Gravity
Constraining neutron star interior properties with transient events from accreting neutron stars and magnetars

Andrew Cumming McGill University
April 25, 2013

PIRSA:13040138
Strong Gravity
Spinning black-hole binaries as gravitational and cosmological probes

Enrico Barausse SISSA International School for Advanced Studies
April 11, 2013

PIRSA:13040082
Strong Gravity
Fundamental Physics with Optically Levitated Dielectric Objects

Asimina Arvanitaki Perimeter Institute for Theoretical Physics
April 04, 2013

PIRSA:13040114
Strong Gravity
Shake, Rattle and Explode: Short GRBs and the Electromagnetic Counterparts of Gravitational Wave Sources

Edo Berger Harvard University
April 02, 2013

PIRSA:13040081
Cosmology

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

Lorenzo Sironi Columbia University
March 21, 2013

PIRSA:13030078
Strong Gravity
The dynamics of asymptotically anti-de Sitter spacetimes

Claude Warnick
March 14, 2013

PIRSA:13030077
Strong Gravity
Exploiting the Strong Gravitational Fields of Neutron Stars to Measure their Properties

Dimitrios Psaltis University of Arizona
February 28, 2013

PIRSA:13020126
Strong Gravity
Gamma Rays at 130 GeV and How They Might Come from Dark Matter

Andrew Frey University of Winnipeg
February 21, 2013

PIRSA:13020139
Cosmology

Strong Gravity
New transport properties of holographic superfluids

Daniel Fernandez University of Iceland
January 10, 2013

PIRSA:13010004
Strong Gravity
Approaches to modeling pulsar magnetospheres

Anatoly Spitkovsky Princeton University
December 06, 2012

PIRSA:12120001
Strong Gravity

Detectable signatures of compact binaries involving neutron stars

Vasileios Paschalidis University of Illinois Urbana-Champaign
May 16, 2013

PIRSA:13050075
Strong Gravity
In this talk I will focus on two topics concerning compact binaries that involve a neutron star companion: a) the fate of and observable signatures from merging white dwarf-neutron star (WDNS) binaries, and b) electromagnetic signals from black hole - neutron star (BHNS) binaries.WDNS systems - the neglected child among compact binaries - generate detectable gravitational waves (GWs) and may also generate observable electromagnetic (EM) signals. One of the most fascinating aspects about these systems is that they are known to exist, but the final fate of massive, merged WDNSs remnants is currently work in progress. Determining the fate of WDNS remnants will be important for interpreting observations from future transient surveys. I will review recent work that provides insight into the physics of WDNSs remnants. Black hole - neutron star systems are among the most promising sources for gravitational waves, and at the same time also possible sources of detectable precursor and aftermath EM signals. I will present recent the results from general relativistic force-free simulations of binary BHNSs and a type of EM precursor signatures expected from these systems.
David Defeats Goliath: How Ultralight Fields Affect The Dynamics of Massive Black Holes

Paolo Pani Instituto Superior Tecnico - Departamento de Física
May 09, 2013

PIRSA:13050001
Strong Gravity
In the last few years several interesting phenomena associated to the interaction between massive black holes and fundamental bosonic fields have been discovered. I present a selection of them, including superradiance instabilities of spin-0, spin-1 and spin-2 fields, floating orbits in extreme-mass ratio inspirals and black-hole spontaneous scalarization. The theoretical potential of these effects
as almost-model-independent smoking guns for exotic particles and modified gravity, as well as their limitations in realistic astrophysical scenarios, are discussed.
Constraining neutron star interior properties with transient events from accreting neutron stars and magnetars

Andrew Cumming McGill University
April 25, 2013

PIRSA:13040138
Strong Gravity
The last few years have seen new opportunities for constraining the physics of neutron star interiors. I will first discuss the current state of neutron star radius measurements and then go on to discuss thermal tomography as a probe of the nuclear, magnetic, and transport properties of neutron star crusts. In each case, I will emphasize the astrophysics that must be understood to make reliable inferences about the properties of dense matter from observations of neutron stars.
Spinning black-hole binaries as gravitational and cosmological probes

Enrico Barausse SISSA International School for Advanced Studies
April 11, 2013

PIRSA:13040082
Strong Gravity
Fundamental Physics with Optically Levitated Dielectric Objects

Asimina Arvanitaki Perimeter Institute for Theoretical Physics
April 04, 2013

PIRSA:13040114
Strong Gravity
In the past few years, optical cooling and manipulating of macroscopic objects, such as micro-mirrors and cantilevers has developed into an active field of research. In mechanical systems, the oscillator is attached to its suspension, a thermal contact that limits the motion isolation. On the other hand, when these small objects are levitated using the radiation pressure force of lasers, the excellent thermal isolation even at room temperatures helps produce very sensitive force detectors, and eventually quantum transducers for quantum computation purposes. These new techniques may have a variety of applications for fundamental physics such as short distance tests of gravity and gravitational wave detection at high frequencies. In addition, there are several proposals suggesting that optically levitated dielectrics can be cooled to the ground state of the center of mass motion, opening the exciting possibility of creating macroscopic matter-wave interferometers.
Shake, Rattle and Explode: Short GRBs and the Electromagnetic Counterparts of Gravitational Wave Sources

Edo Berger Harvard University
April 02, 2013

PIRSA:13040081
Cosmology

Strong Gravity
The bimodality of gamma-ray burst (GRB) durations points to distinct progenitor classes for the long- and short-duration GRBs. While the progenitors of long-duration GRBs are now known to be massive stars, the progenitors of short-duration GRBs remain unidentified. In this talk I will discuss the discovery of short GRB afterglow and their host galaxies, detailed studies of their environments from parsec to galactic scales, and studies of their energetics and beaming. Taken together, these observations point to the coalescence of NS-NS/NS-BH binaries as the most likely progenitors. With the upcoming Advanced LIGO/VIRGO gravitational wave detectors it is therefore possible that short GRBs will be the first detected sources, and I will discuss various approaches to making this connection between gravitational wave and electromagnetic sources.
Particle Acceleration by Magnetic Reconnection in Striped Pulsar Winds and Relativistic Jets

Lorenzo Sironi Columbia University
March 21, 2013

PIRSA:13030078
Strong Gravity
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
Strong Gravity
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
Strong Gravity
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
Cosmology

Strong Gravity
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
Strong Gravity
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
Strong Gravity
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.

Title	Speaker(s)	Date	Talk Type	Info
Detectable signatures of compact binaries involving neutron stars	Vasileios Paschalidis	2013-05-16	Scientific Series	View details
David Defeats Goliath: How Ultralight Fields Affect The Dynamics of Massive Black Holes	Paolo Pani	2013-05-09	Scientific Series	View details
Constraining neutron star interior properties with transient events from accreting neutron stars and magnetars	Andrew Cumming	2013-04-25	Scientific Series	View details
Spinning black-hole binaries as gravitational and cosmological probes	Enrico Barausse	2013-04-11	Scientific Series	View details
Fundamental Physics with Optically Levitated Dielectric Objects	Asimina Arvanitaki	2013-04-04	Scientific Series	View details
Shake, Rattle and Explode: Short GRBs and the Electromagnetic Counterparts of Gravitational Wave Sources	Edo Berger	2013-04-02	Scientific Series	View details
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

Strong Gravity

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