arXiv subjects

Jorge Pullin

Publications and source records attributed to Jorge Pullin.

At least 145 records · Page 8Linked to original sources

arXiv2001

Perturbations of the Kerr spacetime in horizon penetrating coordinates

We derive the Teukolsky equation for perturbations of a Kerr spacetime when the spacetime metric is written in either ingoing or outgoing Kerr-Schild form. We also write explicit formulae for setting up the initial data for the Teukolsky equation in the time domain in terms of a three metric and an extrinsic curvature. The motivation of this work is to have in place a formalism to study the evolution in the ``close limit'' of two recently proposed solutions to the initial value problem in general relativity that are based on Kerr-Schild slicings. A perturbative formalism in horizon penetrating coordinates is also very desirable in connection with numerical relativity simulations using black hole ``excision''.

gr-qc↗

arXiv2001

Matters of Gravity, the newsletter of the APS Topical Group on Gravitation, Spring 2001

News: - APS Prize on gravitation, by Cliff Will - TGG elections, by David Garfinkle - We hear that... by Jorge Pullin Research Briefs: - Experimental Unruh radiation?, by Matt Visser - Why is the universe accelerating?, by Beverly Berger - The Lazarus Project, by Richard Price - LIGO locks its first detector!, by Stan Whitcomb - Progress on the nonlinear r-mode problem, by Keith Lockitch Conference reports: - Analog models of general relativity, by Matt Visser - Astrophysical Sources of Gravitational radiation by Joan Centrella - Numerical relativity at the 20th Texas meeting, by Pablo Laguna

gr-qc↗

arXiv2001

Second order perturbations of a Schwarzschild black hole: inclusion of odd parity perturbations

We consider perturbations of a Schwarzschild black hole that can be of both even and odd parity, keeping terms up to second order in perturbation theory, for the $\ell=2$ axisymmetric case. We develop explicit formulae for the evolution equations and radiated energies and waveforms using the Regge-Wheeler-Zerilli approach. This formulation is useful, for instance, for the treatment in the ``close limit approximation'' of the collision of counterrotating black holes.

gr-qc↗

arXiv2000

Knot theory and quantum gravity in loop space: a primer

These notes summarize the lectures delivered in the V Mexican School of Particle Physics, at the University of Guanajuato. We give a survey of the application of Ashtekar's variables to the quantization of General Relativity in four dimensions with special emphasis on the application of techniques of analytic knot theory to the loop representation. We discuss the role that the Jones Polynomial plays as a generator of nondegenerate quantum states of the gravitational field.

hep-th↗

arXiv2000

Matters of Gravity, the newsletter of the APS Topical Group on Gravitation

Research Briefs: Cosmic microwave background anisotropy experiments, by Sean Carroll LISA Project Update by Bill Folkner An update on the r-mode instability, by Nils Andersson Laboratory experiments: news from MG9, by Riley Newman Progress toward Commissioning the LIGO detectors, by Stan Whitcomb 160 Hours of Data Taken on TAMA300, by Seiji Kawamura Conference reports: Kipfest, by Richard Price Third Capra meeting, by Eric Poisson GR at the XIIIth Congress on Mathematical Physics, by Abhay Ashtekar 3rd International LISA Symposium, by Curt Cutler

gr-qc↗

arXiv2000

Grazing Collisions of Black Holes via the Excision of Singularities

We present the first simulations of non-headon (grazing) collisions of binary black holes in which the black hole singularities have been excised from the computational domain. Initially two equal mass black holes $m$ are separated a distance $\approx10m$ and with impact parameter $\approx2m$. Initial data are based on superposed, boosted (velocity $\approx0.5c$) solutions of single black holes in Kerr-Schild coordinates. Both rotating and non-rotating black holes are considered. The excised regions containing the singularities are specified by following the dynamics of apparent horizons. Evolutions of up to $t \approx 35m$ are obtained in which two initially separate apparent horizons are present for $t\approx3.8m$. At that time a single enveloping apparent horizon forms, indicating that the holes have merged. Apparent horizon area estimates suggest gravitational radiation of about 2.6% of the total mass. The evolutions end after a moderate amount of time because of instabilities.

gr-qc↗

arXiv2000

The large cosmological constant approximation to classical and quantum gravity: model examples

We have recently introduced an approach for studying perturbatively classical and quantum canonical general relativity. The perturbative technique appears to preserve many of the attractive features of the non-perturbative quantization approach based on Ashtekar's new variables and spin networks. With this approach one can find perturbatively classical observables (quantities that have vanishing Poisson brackets with the constraints) and quantum states (states that are annihilated by the quantum constraints). The relative ease with which the technique appears to deal with these traditionally hard problems opens several questions about how relevant the results produced can possibly be. Among the questions is the issue of how useful are results for large values of the cosmological constant and how the approach can deal with several pathologies that are expected to be present in the canonical approach to quantum gravity. With the aim of clarifying these points, and to make our construction as explicit as possible, we study its application in several simple models. We consider Bianchi cosmologies, the asymmetric top, the coupled harmonic oscillators with constant energy density and a simple quantum mechanical system with two Hamiltonian constraints. We find that the technique satisfactorily deals with the pathologies of these models and offers promise for finding (at least some) results even for small values of the cosmological constant. Finally, we briefly sketch how the method would operate in the full four dimensional quantum general relativity case.

gr-qc↗

arXiv2000

Making classical and quantum canonical general relativity computable through a power series expansion in the inverse cosmological constant

We consider general relativity with a cosmological constant as a perturbative expansion around a completely solvable diffeomorphism invariant field theory. This theory is the $Λ\to\infty$ limit of general relativity. This allows an explicit perturbative computational setup in which the quantum states of the theory and the classical observables can be explicitly computed. The zeroth order corresponds to highly degenerate space-times with vanishing volume. Perturbations give rise to space-times with non-vanishing volumes in a natural way. The spectrum of area- and volume-related observables constructed by coupling the theory to matter can be directly assessed. An unexpected relationship arises at a quantum level between the discrete spectrum of the volume operator and the allowed values of the cosmological constant.

gr-qc↗

arXiv2000

Excitation of Neutron Star Oscillations by an Orbiting Particle

The excitation of neutron stars is expected to be an important source of gravitational radiation. Of fundamental importance is then to investigate mechanisms that trigger oscillations in neutron stars in order to characterize the emitted radiation. We present results from a numerical study of the even-parity gravitational radiation generated from a particle orbiting a neutron star. We focus our investigation on those conditions on the orbital parameters that favor the excitation of $w$-modes. We find that, for astrophysically realistic conditions, there is practically no $w$-mode contribution to the emitted radiation. Only for particles with ultra-relativistic orbital speeds $\ge 0.9c$, the $w$-mode does significantly contribute to the total emitted gravitational energy. We also stress the importance of setting consistent initial configurations.

gr-qc↗

arXiv2000

Close limit of grazing black hole collisions: non-spinning holes

Using approximate techniques we study the final moments of the collision of two (individually non-spinnning) black holes which inspiral into each other. The approximation is based on treating the whole space-time as a single distorted black hole. We obtain estimates for the radiated energy, angular momentum and waveforms for the gravitational waves produced in such a collision. The results can be of interest for analyzing the data that will be forthcoming from gravitational wave interferometric detectors, like the LIGO, GEO, LISA, VIRGO and TAMA projects.

gr-qc↗

arXiv2000

Matters of Gravity, the newsletter of the APS Topical Group on Gravitation

News: TGG session in the April meeting, by Cliff Will NRC report, by Beverly Berger MG9 Travel Grant for US researchers, by Jim Isenberg Research Briefs: How many coalescing binaries are there?, by Vicky Kalogera Recent developments in black critical phenomena, by Pat Brady Optical black holes?, by Matt Visser ``Branification:'' an alternative to compactification, by Steve Giddings Searches for non-Newtonian Gravity at Sub-mm Distances, by Riley Newman Quiescent cosmological singularities by Bernd Schmidt The debut of LIGO II, by David Shoemaker Is the universe still accelerating?, by Sean Carroll Conference reports: Journ\' ees Relativistes Weimar 1999, by Volker Perlick The 9th Midwest Relativity Meeting, by Thomas Baumgarte

gr-qc↗

arXiv1999

Canonical quantum gravity in the Vassiliev invariants arena: I. Kinematical structure

We generalize the idea of Vassiliev invariants to the spin network context, with the aim of using these invariants as a kinematical arena for a canonical quantization of gravity. This paper presents a detailed construction of these invariants (both ambient and regular isotopic) requiring a significant elaboration based on the use of Chern-Simons perturbation theory which extends the work of Kauffman, Martin and Witten to four-valent networks. We show that this space of knot invariants has the crucial property -from the point of view of the quantization of gravity- of being loop differentiable in the sense of distributions. This allows the definition of diffeomorphism and Hamiltonian constraints. We show that the invariants are annihilated by the diffeomorphism constraint. In a companion paper we elaborate on the definition of a Hamiltonian constraint, discuss the constraint algebra, and show that the construction leads to a consistent theory of canonical quantum gravity.

gr-qc↗

arXiv1999

Canonical quantum gravity in the Vassiliev invariants arena: II. Constraints, habitats and consistency of the constraint algebra

In a companion paper we introduced a kinematical arena for the discussion of the constraints of canonical quantum gravity in the spin network representation based on Vassiliev invariants. In this paper we introduce the Hamiltonian constraint, extend the space of states to non-diffeomorphism invariant ``habitats'' and check that the off-shell quantum constraint commutator algebra reproduces the classical Poisson algebra of constraints of general relativity without anomalies. One can therefore consider the resulting set of constraints and space of states as a consistent theory of canonical quantum gravity.

gr-qc↗

arXiv1999

Matters of Gravity, The newsletter of the APS Topical Group on Gravitation

Research Briefs: Does the GSL imply an entropy bound?, by Warren G. Anderson A lightweight review of middleweight black holes, by Ben Bromley The physics of isolated horizons, by Daniel Sudarsky LIGO project update, by Stan Whitcomb Meeting reports: Worskhop on initial value for binary black holes, by Carlos Lousto ITP Conference on strong gravitational fields, by Don Marolf Yukawa International Seminar, by John Friedman Minnowbrook symposium on the structure of space-time, by Kamesh Wali Black holes II and CCGRRA 8 by Jack Gegenberg and Gabor Kunstatter Hartlefest & 15th Pacific Coast Gravity Meeting by Simon Ross Second Capra workshop by Patrick Brady and Alan Wiseman Third Edoardo Amaldi Conference, by Gabriela Gonzalez Strings 99, by Thomas Thiemann

gr-qc↗

arXiv1999

The close limit of colliding black holes: an update

This is the writeup of the talk I gave at the Yukawa International Symposium at Kyoto, Japan on June 29, 1999. The talk summarizes the present status of the close limit approximation for colliding black holes.

gr-qc↗

arXiv1999

Inspiralling black holes: the close limit

Using several approximations, we calculate an estimate of the gravitational radiation emitted when two equal mass black holes coalesce at the end of their binary inspiral. We find that about 1% of the mass energy of the pair will emerge as gravitational waves during the final ringdown and a negligible fraction of the angular momentum will be radiated.

gr-qc↗

arXiv1999

Gravitational radiation from Schwarzschild black holes: the second order perturbation formalism

The perturbation theory of black holes has been useful recently for providing estimates of gravitational radiation from black hole collisions. Second order perturbation theory, relatively undeveloped until recently, has proved to be important both for providing refined estimates and for indicating the range of validity of perturbation theory. Here we present the second order formalism for perturbations of Schwarzschild spacetimes. The emphasis is on practical methods for carrying out second order computations of outgoing radiation. General issues are illustrated throughout with examples from ``close-limit'' results, perturbation calculations in which black holes start from small separation.

gr-qc↗

arXiv1999

Matters of Gravity, the newsletter of the APS Topical Group on Gravitation

Contents: Editorial Correspondents News: - Topical Group News, by Jim Isenberg - We hear that..., by Jorge Pullin - The Chandra Satellite, by Beverly Berger Research Briefs: - Analytical event horizons of merging black holes, by Simonetta Frittelli - LIGO project update, by David Shoemaker - Bicentenary of the Cavendish Experiment, by Riley Newman Conference reports: - Eighth Midwest meeting, by Richard Hammond - GWDAW 98, by Sam Finn - Bad Honnef seminar, by Alan Randall.

gr-qc↗