2020-10-19T22:50:21Zhttp://edoc.mpg.de/ac_ft_oai.ploai:edoc.mpg.de:26982009-03-316:84
Formation of the universe : From classical to quantum cosmology
Nicolai, Hermann
Pössel, Markus
notspecified
We give a brief overview of the role of quantum theory in cosmology, reviewing the standard model of classical cosmology, inflation and quantum cosmology. Plenary Talk given by H. Nicolai on December 13, 2000 at the Quantum Theory Centenary ''''100 Jahre Quantentheorie, Berlin
2001
Article
http://edoc.mpg.de/2698
urn:ISSN:1521-3889
info:doi/10.1002/1521-3889(200102)10:1/2<123::AID-ANDP123>3.0.CO;2-B
Annalen der Physik, v.10, 123-130 (2001)
en
oai:edoc.mpg.de:26992009-03-206:83
Complete null data for a black hole collision
Husa, Sascha
Gomez, Roberto
Winicour, Jeffrey
notspecified
We discuss a sequence of numerically constructed geometries describing binary black hole event horizons -- providing the necessary input for characteristic evolution of the exterior spacetime. Our sequence approaches a single Schwarzschild horizon as one limiting case and also includes cases where the horizon's crossover surface is not hidden by a marginally anti-trapped surface (MATS).
2001
Article
http://edoc.mpg.de/2699
Physical Review D, v.64, 024010 (2001)
en
oai:edoc.mpg.de:27002009-03-196:85
Cactus Tools for Grid Applications
Allen, Gabrielle
Benger, Werner
Dramlitsch, Thomas
Goodale, Tom
Hege, Hans-Christian
Lanfermann, Gerd
Merzky, Andre
Radke, Thomas
Seidel, Edward
Shalf, John
notspecified
Cactus is an open source problem solving environment designed for scientists and engineers. Its modular structure facilitates parallel computation across different architectures and collaborative code development between different groups. The Cactus Code originated in the academic research community, where it has been developed and used over many years by a large international collaboration of physicists and computational scientists. We discuss here how the intensive computing requirements of physics applications now using the Cactus Code encourage the use of distributed and metacomputing, and detail how its design makes it an ideal application test-bed for Grid computing. We describe the development of tools, and the experiments which have already been performed in a Grid environment with Cactus, including distributed simulations, remote monitoring and steering, and data handling and visualization. Finally, we discuss how Grid portals, such as those already developed for Cactus, will open the door to global computing resources for scientific users.
2001
Article
http://edoc.mpg.de/2700
Cluster Computing, v.4, 179-188 (2001)
en
oai:edoc.mpg.de:27012009-03-316:84
Microlocal spectrum condition and Hadamard form for vector-valued quantum fields in curved spacetime
Sahlmann, Hanno
Verch, Rainer
notspecified
The characterization of Hadamard states in terms of a specific form of the wavefront set of their two-point functions has been developed some years ago by Radzikowski for scalar fields on a four-dimensional globally hyperbolic spacetime, and initiated a major progress in the understanding of Hadamard states and the further development of quantum field theory in curved spacetime. In the present work, the characterization of Hadamard states through a particular form of the wavefront set of their two-point functions will be generalized from scalar fields to vector fields (sections in a vector bundle) which are subject to a wave-equation and are quantized so as to fulfill the covariant canonical commutation relations, or which obey a Dirac equation and are quantized according to the covariant anti-commutation relations, in any globally hyperbolic spacetime having dimension three or higher. In proving this result, a gap which is present in the published proof for the scalar field case will be removed. Moreover we determine the short-distance scaling limits of Hadamard states for vector-bundle valued fields, finding them to coincide with the corresponding flat-space, massless vacuum states.
2001
Article
http://edoc.mpg.de/2701
Reviews in Mathematical Physics, v.13, 1203-1246 (2001)
en
oai:edoc.mpg.de:27022009-03-166:82
Plunge waveforms from inspiralling binary black holes
Baker, John G.
Brügmann, Bernd
Campanelli, Manuela
Lousto, Carlos O.
Takahashi, Ryoji
notspecified
We study the coalescence of non-spinning binary black holes from the innermost stable circular orbit down to the final single rotating black hole. We use a technique that combines the full numerical approach to solve Einstein equations, applied in the truly nonlinear regime, and linearized perturbation theory around the final distorted single black hole at later times. We compute the plunge waveforms which present a non negligible signal lasting for over $tsim 100$M showing early nonlinear ringing. We also obtain estimates of the total gravitational energy radiated during this process and the plunging time.
2001
Article
http://edoc.mpg.de/2702
Physical Review Letters, v.87, 121103 (2001)
en
oai:edoc.mpg.de:27032009-03-316:84
On non-commutative N=2 Super Yang Mills
Armoni, Adi
Minasian, Ruben
Theisen, Stefan
notspecified
We discuss the Seiberg-Witten solution of the non-commutative N=2 U(N) SYM model. The solution is described in terms of the ordinary Seiberg-Witten curve of the SU(N) theory plus an additional free U(1). Hence, at the two-derivative approximation the theory flows to the ordinary commutative theory in the infra-red (k<1/sqrt(theta)). In particular, the center U(1) is free and it decouples from the other U(1)s. In addition, no UV/IR mixing is found.
2001
Article
http://edoc.mpg.de/2703
urn:ISSN:0370-2693
info:doi/10.1016/S0370-2693(01)00763-8
Physics Letters B, v.513, 406-412 (2001)
en
oai:edoc.mpg.de:27042009-03-316:84
Coherent States for Canonical Quantum General Relativity and the Infinite Tensor Product Extension
Sahlmann, Hanno
Thiemann, Thomas
Winkler, Oliver
notspecified
We summarize a recently proposed concrete programme for investigating the (semi)classical limit of canonical, Lorentzian, continuum quantum general relativity in four spacetime dimensions. The analysis is based on a novel set of coherent states labelled by graphs. These fit neatly together with an Infinite Tensor Product (ITP) extension of the currently used Hilbert space. The ITP construction enables us to give rigorous meaning to the infinite volume (thermodynamic) limit of the theory which has been out of reach so far.
2001
Article
http://edoc.mpg.de/2704
Nuclear Physics B, v.606, 401-440 (2001)
en
oai:edoc.mpg.de:27052009-03-316:84
R^4 couplings, the fundamental membrane and exceptional theta correspondences
Pioline, Boris
Nicolai, Hermann
Plefka, Jan
Waldron, Andrew
notspecified
This letter is an attempt to carry out a first-principle computation in M-theory using the point of view that the eleven-dimensional membrane gives the fundamental degrees of freedom of M-theory. Our aim is to derive the exact BPS $R^4$ couplings in toroidal compactifications of M-theory from the toroidal BPS membrane, by pursuing the analogy with the one-loop string theory computation. We exhibit an $Sl(3,Zint)$ modular invariance hidden in the light-cone gauge (but obvious in the Polyakov approach), and recover the correct classical spectrum and membrane instantons; the summation measure however is off. We argue that the correct membrane amplitude should be given by an exceptional theta correspondence lifting $Sl(3,Zint)$ modular forms to $exc(Zint)$ automorphic forms, generalizing the usual theta lift between $Sl(2,Zint)$ and $SO(d,d,Zint)$ in string theory, and outline the construction of such objects. The exceptional correspondence $Sl(3)imes E_6subset E_8$ offers the interesting prospect of solving the membrane small volume divergence and unifying membranes with five-branes.
2001
Article
http://edoc.mpg.de/2705
urn:ISSN:1126-6708
info:doi/10.1088/1126-6708/2001/03/036
Journal of High Energy Physics, v.03 (2001)
en
oai:edoc.mpg.de:27062009-03-206:83
Characteristic Evolution and Matching
Winicour, Jeffrey
notspecified
I review the development of numerical evolution codes for general relativity based upon the characteristic initial value problem. Progress is traced from the early stage of 1D feasibility studies to current 3D black codes that simulate binary black holes. A prime application of characteristic evolution is Cauchy-characteristic matching, which is also reviewed.
2001
Article
http://edoc.mpg.de/2706
Living Reviews in Relativity, v.3 (2001)
en
oai:edoc.mpg.de:27122009-03-206:83
Asymptotically Flat Initial Data with Prescribed Regularity at Infinity
Dain, Sergio
Friedrich, Helmut
We prove the existence of a large class of asymptotically flat initial data with non-vanishing mass and angular momentum for which the metric and the extrinsic curvature have asymptotic expansions at space-like infinity in terms of powers of a radial coordinate.
2001
Article
http://edoc.mpg.de/2712
Communications in Mathematical Physics, v.222, 569-609 (2001)
en
oai:edoc.mpg.de:27132009-03-206:83
Initial data for two Kerr-like black holes
Dain, Sergio
notspecified
We prove the existence of a family of initial data for the Einstein vacuum equation which can be interpreted as the data for two Kerr-like black holes in arbitrary location and with spin in arbitrary direction. When the mass parameter of one of them is zero, this family reduces exactly to the Kerr initial data. The existence proof is based on a general property of the Kerr metric which can be used in other constructions as well. Further generalizations are also discussed.
2001
Article
http://edoc.mpg.de/2713
Physical Review Letters, v.87, 121101 (2001)
en
oai:edoc.mpg.de:27142009-03-316:84
Compact and Noncompact Gauged Maximal Supergravities in Three Dimensions
Nicolai, Hermann
Samtleben, Henning
notspecified
We present the maximally supersymmetric three-dimensional gauged supergravities. Owing to the special properties of three dimensions -- especially the on-shell duality between vector and scalar fields, and the purely topological character of (super)gravity -- they exhibit an even richer structure than the gauged supergravities in higher dimensions. The allowed gauge groups are subgroups of the global E_8 symmetry of ungauged N=16 supergravity. They include the regular series SO(p,8-p) x SO(p,8-p) for all p=0,1,...,4, the group E_8 itself, as well as various noncompact forms of the exceptional groups E_7, E_6 and F_4 x G_2. We show that all these theories admit maximally supersymmetric ground states, and determine their background isometries, which are superextensions of the anti-de Sitter group SO(2,2). The very existence of these theories is argued to point to a new supergravity beyond the standard D=11 supergravity.
2001
Article
http://edoc.mpg.de/2714
urn:ISSN:1126-6708
info:doi/10.1088/1126-6708/2001/04/022
Journal of High Energy Physics, v.04 (2001)
en
oai:edoc.mpg.de:27152009-03-316:84
Jet coordinates for local BRST cohomology
Brandt, Friedemann
notspecified
The construction of appropriate jet space coordinates for calculating local BRST cohomology groups is discussed. The relation to tensor calculus is briefly reviewed too.
2001
Article
http://edoc.mpg.de/2715
Letters in Mathematical Physics, v.55, 149-159 (2001)
en
oai:edoc.mpg.de:27162009-03-316:84
A proper-time cure for the conformal sickness in quantum gravity
Dasgupta, Arundhati
Loll, Renate
notspecified
Starting from the space of Lorentzian metrics, we examine the full gravitational path integral in 3 and 4 space-time dimensions. Inspired by recent results obtained in a regularized, dynamically triangulated formulation of Lorentzian gravity, we gauge-fix to proper-time coordinates and perform a non-perturbative ''''Wick rotation'' on the physical configuration space. Under certain assumptions about the behaviour of the partition function under renormalization, we find that the divergence due to the conformal modes of the metric is cancelled non-perturbatively by a Faddeev-Popov determinant contributing to the effective measure. We illustrate some of our claims by a 3d perturbative calculation.
2001
Article
http://edoc.mpg.de/2716
Nuclear Physics B, v.606, 357-379 (2001)
en
oai:edoc.mpg.de:27172009-03-166:82
Black Hole Excision for Dynamic Black Holes
Alcubierre, Miguel
Brügmann, Bernd
Pollney, Denis
Seidel, Edward
notspecified
We extend previous work on 3D black hole excision to the case of distorted black holes, with a variety of dynamic gauge conditions that are able to respond naturally to the spacetime dynamics. We show that the combination of excision and gauge conditions we use is able to drive highly distorted, rotating black holes to an almost static state at late times, with well behaved metric functions, without the need for any special initial conditions or analytically prescribed gauge functions. Further, we show for the first time that one can extract accurate waveforms from these simulations, with the full machinery of excision and dynamic gauge conditions. The evolutions can be carried out for long times, far exceeding the longevity and accuracy of even better resolved 2D codes. While traditional 2D codes show errors in quantities such as apparent horizon mass of over 100% by t = 100M, and crash by t = 150M, with our new techniques the same systems can be evolved for hundreds of M's in full 3D with errors of only a few percent.
2001
Article
http://edoc.mpg.de/2717
Physical Review D, v.64, 061501 (2001)
en
oai:edoc.mpg.de:27182009-03-166:82
The Lazarus project : A pragmatic approach to binary black hole
Baker, John G.
Campanelli, Manuela
Lousto, Carlos O.
notspecified
We present a detailed description of techniques developed to combine 3D numerical simulations and, subsequently, a single black hole close-limit approximation. This method has made it possible to compute the first complete waveforms covering the post-orbital dynamics of a binary black hole system with the numerical simulation covering the essential non-linear interaction before the close limit becomes applicable for the late time dynamics. To determine when close-limit perturbation theory is applicable we apply a combination of invariant a priori estimates and a posteriori consistency checks of the robustness of our results against exchange of linear and non-linear treatments near the interface. Once the merically modeled binary system reaches a regime that can be treated as perturbations of the Kerr spacetime, we must approximately relate the numerical coordinates to the perturbative background coordinates. We also perform a rotation of a numerically defined tetrad to asymptotically reproduce the tetrad required in the perturbative treatment. We can then produce numerical Cauchy data for the close-limit evolution in the form of the Weyl scalar $psi_4$ and its time derivative $partial_tpsi_4$ with both objects being first order coordinate and tetrad invariant. The Teukolsky equation in Boyer-Lindquist coordinates is adopted to further continue the evolution. To illustrate the application of these techniques we evolve a single Kerr hole and compute the spurious radiation as a measure of the error of the whole procedure. We also briefly discuss the extension of the project to make use of improved full numerical evolutions and outline the approach to a full understanding of astrophysical black hole binary systems which we can now pursue.
2002
Article
http://edoc.mpg.de/2718
Physical Review D, v.65 (2002)
en
oai:edoc.mpg.de:27192009-03-316:84
Hyperbolic Kac Moody Algebras and Chaos in Kaluza Klein Models
Damour, Thibault
Henneaux, Marc
Julia, Bernard
Nicolai, Hermann
notspecified
Some time ago, it was found that the never-ending oscillatory chaotic behaviour discovered by Belinsky, Khalatnikov and Lifshitz (BKL) for the generic solution of the vacuum Einstein equations in the vicinity of a spacelike ("cosmological") singularity disappears in spacetime dimensions $D= d+1>10$. Recently, a study of the generalization of the BKL chaotic behaviour to the superstring effective Lagrangians has revealed that this chaos is rooted in the structure of the fundamental Weyl chamber of some underlying hyperbolic Kac-Moody algebra. In this letter, we show that the same connection applies to pure gravity in any spacetime dimension $geq 4$, where the relevant algebras are $AE_d$. In this way the disappearance of chaos in pure gravity models in $D > 10$ dimensions becomes linked to the fact that the Kac-Moody algebras $AE_d$ are no longer hyperbolic for $d > 9$.
2001
Article
http://edoc.mpg.de/2719
urn:ISSN:0370-2693
info:doi/10.1016/S0370-2693(01)00498-1
Physics Letters B, v.509, 323-330 (2001)
en
oai:edoc.mpg.de:27212009-03-166:82
Gravitational Wave Damping of Neutron Star Wobble
Cutler, Curt
Jones, David Ian
notspecified
We calculate the effect of gravitational wave (gw) back-reaction on realistic neutron stars (NS's) undergoing torque-free precession. By ''realistic' we mean that the NS is treated as a mostly-fluid body with an elastic crust, as opposed to a rigid body. We find that gw's damp NS wobble on a timescale tau_{theta} approx 2 x 10^5 yr [10^{-7}/(DId/I_0)]^2 (kHz/ nu_s)^4, where nu_s is the spin frequency and DId is the piece of the NS's inertia tensor that "follows" the crust's principal axis (as opposed to its spin axis). We give two different derivations of this result: one based solely on energy and angular momentum balance, and another obtained by adding the Burke-Thorne radiation reaction force to the Newtonian equations of motion. This problem was treated long ago by Bertotti and Anile (1973), but their claimed result is wrong. When we convert from their notation to ours, we find that their tau_{theta} is too short by a factor of order 10^5 for typical cases of interest, and even has the wrong sign for DId negative. We show where their calculation went astray.
2001
Article
http://edoc.mpg.de/2721
Physical Review D, v.63, 024002 (2001)
en
oai:edoc.mpg.de:27222009-03-316:84
Superstring BRST cohomology
Brandt, Friedemann
Kling, Alexander
Kreuzer, Maximilian
notspecified
We first derive all world-sheet action functionals for NSR superstring models with (1,1) supersymmetry and any number of abelian gauge fields, for gauge transformations of the standard form. Then we prove for these models that the BRST cohomology groups $H^g(s)$, $g<4$ (with the antifields taken into account) are isomorphic to those of the corresponding bosonic string models, whose cohomology is fully known. This implies that the nontrivial global symmetries, Noether currents, background charges, consistent deformations and candidate gauge anomalies of an NSR (1,1) superstring model are in one-to-one correspondence with their bosonic counterparts.
2001
Article
http://edoc.mpg.de/2722
Journal of High Energy Physics, v.08 (2001)
en
oai:edoc.mpg.de:27232009-03-206:83
The Wahlquist-Newman solution
Mars, Marc
notspecified
Based on a geometrical property which holds both for the Kerr metric and for the Wahlquist metric we argue that the Kerr metric is a vacuum subcase of the Wahlquist perfect-fluid solution. The Kerr-Newman metric is a physically preferred charged generalization of the Kerr metric. We discuss which geometric property makes this metric so special and claim that a charged generalization of the Wahlquist metric satisfying a similar property should exist. This is the Wahlquist-Newman metric, which we present explicitly in this paper. This family of metrics has eight essential parameters and contains the Kerr-Newman-de Sitter and the Wahlquist metrics, as well as the whole Plebanski limit of the rotating C-metric, as particular cases. We describe the basic geometric properties of the Wahlquist-Newman metric, including the electromagnetic field and its sources, the static limit of the family and the extension of the spacetime across the horizon.
2001
Article
http://edoc.mpg.de/2723
Physical Review D, v.63, 064022 (2001)
en
oai:edoc.mpg.de:27242009-03-206:83
Spacetime Ehlers group : Transformation law for the Weyl tensor
Mars, Marc
notspecified
The spacetime Ehlers group, which is a symmetry of the Einstein vacuum field equations for strictly stationary spacetimes, is defined and analyzed in a purely spacetime context (without invoking the projection formalism). In this setting, the Ehlers group finds its natural description within an infinite dimensional group of transformations that maps Lorentz metrics into Lorentz metrics and which may be of independent interest. The Ehlers group is shown to be well defined independently of the causal character of the Killing vector (which may become null on arbitrary regions). We analyze which global conditions are required on the spacetime for the existence of the Ehlers group. The transformation law for the Weyl tensor under Ehlers transformations is explicitly obtained. This allows us to study where, and under which circumstances, curvature singularities in the transformed spacetime will arise. The results of the paper are applied to obtain a local characterization of the Kerr-NUT metric.
2001
Article
http://edoc.mpg.de/2724
Classical and Quantum Gravity, v.18, 719-738 (2001)
en
oai:edoc.mpg.de:27252009-03-206:83
On the uniqueness of the Einstein-Straus model
Mars, Marc
notspecified
We show that the Einstein-Straus model does not give a robust answer to the problem of the influence of the cosmic expansion on the local physics. This is done by finding the most general static region embeddable in a Friedman-Lemaitre-Robertson-Walker expanding cosmology and showing that the model must be almost spherically symmetric. More precisely, we show that the boundary of the static region must be a two-sphere at each instant of cosmic time. The motion of this two-sphere in spacetime is as follows: its would-be center (if there was no static region) moves along a path whose projection on any 3-space of constant cosmic time is a geodesic with respect to the induced 3-metric. The velocity of this geodesic is determined from the matching. In particular, this center must be at rest with respect to the cosmologic flow (thus giving a spherically symmetric model) when any of the standard energy-momentum tensors inside the static region is imposed.
2001
Article
http://edoc.mpg.de/2725
Classical and Quantum Gravity, v.18, 3645-3663 (2001)
en
oai:edoc.mpg.de:27262009-03-206:83
Initial data for a head on collision of two Kerr-like black holed with close limit
Dain, Sergio
notspecified
We prove the existence of a family of initial data for the Einstein vacuum equation which can be interpreted as the data for two Kerr-like black holes in arbitrary location and with spin in arbitrary direction. This family of initial data has the following properties: (i) When the mass parameter of one of them is zero or when the distance between them goes to infinity, it reduces exactly to the Kerr initial data. (ii) When the distance between them is zero, we obtain exactly a Kerr initial data with mass and angular momentum equal to the sum of the mass and angular momentum parameters of each of them. The initial data depends smoothly on the distance, the mass and the angular momentum parameters.
2001
Article
http://edoc.mpg.de/2726
Physical Review D, v.64, 124002 (2001)
en
oai:edoc.mpg.de:27272009-03-316:84
Exceptional non-renormalization properties and OPE analysis of chiral four-point functions in N=4 SYM_4
Arutyunov, Gleb
Eden, Burkhard U.
Petkou, Anastasios C.
Sokatchev, E.
notspecified
We show that certain classes of apparently unprotected operators in N=4 SYM_4 do not receive quantum corrections as a consequence of a partial non-renormalization theorem for the 4-point function of chiral primary operators. We develop techniques yielding the asymptotic expansion of the 4-point function of CPOs up to order O(lambda^2) and we perform a detailed OPE analysis. Our results reveal the existence of new non-renormalized operators of approximate dimension 6.
2002
Article
http://edoc.mpg.de/2727
Nuclear Physics B, v.620, 380-404 (2002)
en
oai:edoc.mpg.de:27282009-03-316:84
Open Membranes, p-Brane and Noncommutativity of Boundary String Coordinates
Das, Ashok
Maharana, Jnanadeva
Melikyan, Arsen
notspecified
We study the dynamics of an open membrane with a cylindrical topology, in the background of a constant three form, whose boundary is attached to p-branes. The boundary closed string is coupled to a two form potential to ensure gauge invariance. We use the action, due to Bergshoeff, London and Townsend, to study the noncommutativity properties of the boundary string coordinates. The constrained Hamiltonian formalism due to Dirac is used to derive the noncommutativity of coordinates. The chain of constraints is found to be finite for a suitable gauge choice, unlike the case of the static gauge, where the chain has an infinite sequence of terms. It is conjectured that the formulation of closed string field theory may necessitate introduction of a star product which is both noncommutative and nonassociative.
2001
Article
http://edoc.mpg.de/2728
Journal of High Energy Physics, v.04, 016 (2001)
en
oai:edoc.mpg.de:27292009-03-206:83
Manufacture of Gowdy spacetimes with spikes
Rendall, Alan D.
Weaver, Marsha
notspecified
In numerical studies of Gowdy spacetimes evidence has been found for the development of localized features (''spikes') involving large gradients near the singularity. The rigorous mathematical results available up to now did not cover this kind of situation. In this work we show the existence of large classes of Gowdy spacetimes exhibiting features of the kind discovered numerically. These spacetimes are constructed by applying certain transformations to previously known spacetimes without spikes. It is possible to control the behaviour of the Kretschmann scalar near the singularity in detail. This curvature invariant is found to blow up in a way which is non-uniform near the spike in some cases. When this happens it demonstrates that the spike is a geometrically invariant feature and not an artefact of the choice of variables used to parametrize the metric. We also identify another class of spikes which are artefacts. The spikes produced by our method are compared with the results of numerical and heuristic analyses of the same situation.
2001
Article
http://edoc.mpg.de/2729
Classical and Quantum Gravity, v.18, 2959-2975 (2001)
en
oai:edoc.mpg.de:27302009-03-206:83
The future asymptotics of Bianchi VIII vacuum solutions
Ringström, Hans
notspecified
Bianchi VIII vacuum solutions to Einstein's equations are causally geodesically complete to the future, given an appropriate time orientation, and the objective of this paper is to analyse the asymptotic behaviour of solutions in this time direction. For the Bianchi class A spacetimes, there is a formulation of the field equations that was presented in an article by Wainwright and Hsu, and we will analyse the asymptotic behaviour of solutions in these variables. We also try to give the analytic results a geometric interpretation by analysing how a normalized version of the Riemannian metric on the spatial hypersurfaces of homogeneity evolves
2001
Article
http://edoc.mpg.de/2730
Classical and Quantum Gravity, v.18, 3791-3823 (2001)
en
oai:edoc.mpg.de:27312009-03-316:84
Gauge theories of spacetime symmetries
Brandt, Friedemann
notspecified
Gauge theories of conformal spacetime symmetries are presented which merge features of Yang-Mills theory and general relativity in a new way. The models are local but nonpolynomial in the gauge fields, with a nonpolynomial structure that can be elegantly written in terms of a metric (or vielbein) composed of the gauge fields. General relativity itself emerges from the construction as a gauge theory of spacetime translations. The role of the models within a general classification of consistent interactions of gauge fields is discussed as well.
2001
Article
http://edoc.mpg.de/2731
Physical Review D, v.64, 065025 (2001)
en
oai:edoc.mpg.de:27322009-03-316:84
Quantum corrections for (anti)-evaporating black hole
Buric, Maja
Radovanovic, Voja
notspecified
In this paper we analyse the quantum correction for Schwarzschild black hole in the Unruh state in the framework of spherically symmetric gravity (SSG) model. SSG is a two-dimensional dilaton model which is obtained by spherically symmetric reduction from the four-dimensional theory. We find the one-loop geometry of the (anti)-evaporating black hole and corrections for mass, entropy and apparent horizon.
2001
Article
http://edoc.mpg.de/2732
Physical Review D, v.63, 044020 (2001)
en
oai:edoc.mpg.de:27332009-04-066:83
Oscillatory approach the singularity in vacuum spacetimes with T2 isometry
Berger, Beverly K.
Isenberg, James
Weaver, Marsha
notspecified
We use qualitative arguments combined with numerical simulations to argue that, in the approach to the singularity in a vacuum solution of Einstein's equations with T2 isometry, the evolution at a generic point in space is an endless succession of Kasner epochs, punctuated by bounces in which either a curvature term or a twist term becomes important in the evolution equations for a brief time. Both curvature bounces and twist bounces may be understood within the context of local mixmaster dynamics although the latter have never been seen before in spatially inhomogeneous cosmological spacetimes.
2001
Article
http://edoc.mpg.de/2733
Physical Review D, v.64, 084006 (2001)
en
oai:edoc.mpg.de:27342009-03-316:84
Infinite Kinematic Self-Similarity and Perfect Fluid Spacetimes
Sintes, Alicia M.
Benoit, Patricia M.
Coley, Alan A.
notspecified
Perfect fluid spacetimes admitting a kinematic self-similarity of infinite type are investigated. In the case of plane, spherically or hyperbolically symmetric space-times the field equations reduce to a system of autonomous ordinary differential equations. The qualitative properties of solutions of this system of equations, and in particular their asymptotic behavior, are studied. Special cases, including some of the invariant sets and the geodesic case, are examined in detail and the exact solutions are provided. The class of solutions exhibiting physical self-similarity are found to play an important role in describing the asymptotic behavior of the infinite kinematic self-similar models.
2001
Article
http://edoc.mpg.de/2734
General Relativity and Gravitation, v.33, 1863-1895 (2001)
en
oai:edoc.mpg.de:27352009-03-316:84
Dynamically Triangulating Lorentzian Quantum Gravity
Ambjörn, Jan
Jurkiewicz, Jerzy
Loll, Renate
notspecified
Fruitful ideas on how to quantize gravity are few and far between. In this paper, we give a complete description of a recently introduced non-perturbative gravitational path integral whose continuum limit has already been investigated extensively in d < 4, with promising results. It is based on a simplicial regularization of Lorentzian spacetimes and, most importantly, possesses a well-defined, non-perturbative Wick rotation. We present a detailed analysis of the geometric and mathematical properties of the discretized model in d = 3, 4. This includes a derivation of Lorentzian simplicial manifold constraints, the gravitational actions and their Wick rotation. We define a transfer matrix for the system and show that it leads to a well-defined self-adjoint Hamiltonian. In view of numerical simulations, we also suggest sets of Lorentzian Monte Carlo moves. We demonstrate that certain pathological phases found previously in Euclidean models of dynamical riangulations cannot be realized in the Lorentzian case. (C) 2001 Elsevier Science B.V. All rights reserved
2001
Article
http://edoc.mpg.de/2735
Nuclear Physics B, v.610, 347-382 (2001)
en
oai:edoc.mpg.de:27362009-03-206:83
On blowup for Yang-Mills fields
Bizon, Piotr
Tabor, Z.
notspecified
We study development of singularities for the spherically symmetric Yang-Mills equations in $d+1$ dimensional Minkowski spacetime for $d=4$ (the critical dimension) and $d=5$ (the lowest supercritical dimension). Using combined numerical and analytical methods we show in both cases that generic solutions starting with sufficiently large initial data blow up in finite time. The mechanism of singularity formation depends on the dimension: in $d=5$ the blowup is exactly self-similar while in $d=4$ the blowup is only approximately self-similar and can be viewed as the adiabatic shrinking of the marginally stable static solution. The threshold for blowup and the connection with critical phenomena in the gravitational collapse (which motivated this research) are also briefly discussed.
2001
Article
http://edoc.mpg.de/2736
Physical Review D, v.64, 121701 (2001)
en
oai:edoc.mpg.de:27382009-03-316:84
Boundary Superstring Field Theory Annulus Partition Function in the Presence of Tachyons
Arutyunov, Gleb
Pankiewicz, Ari
Stefanski, Bogdan
notspecified
We compute the Boundary Superstring Field Theory partition function on the annulus in the presence of independent linear tachyon profiles on the two boundaries. The R-R sector is found to contribute non-trivially to the derivative terms of the space-time effective action. In the process we construct a boundary state description of D-branes in the presence of a linear tachyon. We quantize the open string in a tachyonic background and address the question of open/closed string duality.
2001
Article
http://edoc.mpg.de/2738
Journal of High Energy Physics, v.06, 049 (2001)
en
oai:edoc.mpg.de:27392009-03-316:84
On nonrenormalization and OPE in superconformal field theories
Arutyunov, Gleb
Eden, Burkhard U.
Sokatchev, E.
notspecified
The OPE of two N=2 R-symmetry current (short) multiplets is determined by the possible superspace three-point functions that two such multiplets can form with a third, a priori long multiplet. We show that the shortness conditions on the former put strong restrictions on the quantum numbers of the latter. In particular, no anomalous dimension is allowed unless the third supermultiplet is an R-symmetry singlet. This phenomenon should explain many known non-renormalization properties of correlation functions, including the one of four stress-tensor multiplets in N=4 SYM_4
2001
Article
http://edoc.mpg.de/2739
Nuclear Physics B, v.619, 359-372 (2001)
en
oai:edoc.mpg.de:27402009-03-316:84
Lorentzian 3d gravity with wormholes via matrix models
Ambjörn, Jan
Jurkiewicz, Jerzy
Loll, Renate
Vernizzi, Graziano
notspecified
We uncover a surprising correspondence between a non-perturbative formulation of three-dimensional Lorentzian quantum gravity and a hermitian two-matrix model with ABAB-interaction. The gravitational transfer matrix can be expressed as the logarithm of a two-matrix integral, and we deduce from the known structure of the latter that the model has two phases. In the phase of weak gravity, well-defined two-dimensional universes propagate in proper time, whereas in the strong-coupling phase the spatial hypersurfaces disintegrate into many components connected by wormhole
2001
Article
http://edoc.mpg.de/2740
Journal of High Energy Physics, v.09, 022 (2001)
en
oai:edoc.mpg.de:27412009-04-276:83
Boundary conditions in linearized harmonic gravity
Szilagyi, Bela
Schmidt, Bernd
Winicour, Jeffrey
expertsonly
We investigate the initial-boundary value problem for linearized gravitational theory in harmonic coordinates. Rigorous techniques for hyperbolic systems are applied to establish well-posedness for various reductions of the system into a set of six wave equations. The results are used to formulate computational algorithms for Cauchy evolution in a 3-dimensional bounded domain. Numerical codes based upon these algorithms are shown to satisfy tests of robust stability for random constraint violating initial data and random boundary data; and shown to give excellent performance for the evolution of typical physical data. The results are obtained for plane boundaries as well as piecewise cubic spherical boundaries cut out of a Cartesian grid.
2002
Article
http://edoc.mpg.de/2741
Physical Review D, v.65 (2002)
en
oai:edoc.mpg.de:27422009-03-316:84
N=8 matter coupled AdS_3 supergravities
Nicolai, Hermann
Samtleben, Henning
notspecified
Following the recent construction of maximal (N=16) gauged supergravity in three dimensions, we derive gauged D=3, N=8 supergravities in three dimensions as deformations of the corresponding ungauged theories with scalar manifolds SO(8,n)/(SO(8)x SO(n)). As a special case, we recover the N=(4,4) theories with local SO(4) = SO(3)_L x SO(3)_R, which reproduce the symmetries and massless spectrum of D=6, N=(2,0) supergravity compactified on AdS_3 x S^3.
2001
Article
http://edoc.mpg.de/2742
urn:ISSN:0370-2693
info:doi/10.1016/S0370-2693(01)00779-1
Physics Letters B, v.514, 165-172 (2001)
en
oai:edoc.mpg.de:27432009-03-206:83
Conserved quantities in a black hole collision
Dain, Sergio
Valiente-Kroon, Juan Antonio
notspecified
The Newman-Penrose constants of the spacetime corresponding to the development of the Brill-Lindquist initial data are calculated by making use of a particular representation of spatial infinity due to H Friedrich. The Brill-Lindquist initial data set represents the head-on collision of two non-rotating black holes. In this case one non-zero constant is obtained. Its value is given in terms of the product of the individual masses of the black holes and the square of a distance parameter separating the two black holes. This constant retains its value all along null infinity, and therefore it provides information about the late time evolution of the collision process. In particular, it is argued that the magnitude of the constants provides information about the amount of residual radiation contained in the spacetime after the collision of the black holes.
2002
Article
http://edoc.mpg.de/2743
Classical and Quantum Gravity, v.19, 811-815 (2002)
en
oai:edoc.mpg.de:27442009-03-206:83
Can one detect a non-smooth null infinity?
Valiente-Kroon, Juan Antonio
notspecified
It is shown that the precession of a gyroscope can be used to elucidate the nature of the smoothness of the null infinity of an asymptotically flat spacetime (describing an isolated body). A model is proposed for which the effects of precession in the non-smooth null infinity case are of the order r-2ln r. In contrast, in the smooth version the effects are of the order r-3. This difference should provide an effective criterion to decide on the nature of the smoothness of null infinity.
2001
Article
http://edoc.mpg.de/2744
Classical and Quantum Gravity, v.18, 4311-4316 (2001)
en
oai:edoc.mpg.de:27452009-05-266:83
Bondi-type systems near space-like infinity and the calculation of the NP-constants
Friedrich, Helmut
Kannar, Janos
notspecified
We relate Bondi systems near spacelike infinity to another type of gauge conditions. While the former are based on null infinity, the latter are defined in terms of Einstein propagation, the conformal structure, and data on some Cauchy hypersurface. For a certain class of time symmetric space-times we study an expansion which allows us to determine the behavior of various fields arising in Bondi systems in the region of space-time where null infinity touches spacelike infinity. The coefficients of these expansions can be read off from the initial data. We obtain, in particular, expressions for the constants discovered by Newman and Penrose in terms of the initial data. For this purpose we calculate a certain expansion introduced by Friedrich [J. Geom. Phys. 24, 83-163 (1998)] up to third order. (C) 2000 American Institute of Physics. [S0022-2488(00)02602-5].
2000
Article
http://edoc.mpg.de/2745
Journal of Mathematical Physics, v.41, 2195-2232 (2000)
en
oai:edoc.mpg.de:27462009-03-166:82
Gravitational self force by mode sum regularization
Barack, Leor
notspecified
We propose a practical scheme for calculating the local gravitational self-force experienced by a test mass particle moving in a black hole spacetime. The method---equally effective for either weak or strong field orbits---employs the {em mode-sum regularization scheme} previously developed for a scalar toy model. The starting point for the calculation, in this approach, is the formal expression for the regularized self-force derived by Mino et al. (and, independently, by Quinn and Wald), which involves a worldline integral over the tail part of the retarded Green's function. This force is decomposed into multipole (tensor harmonic) modes, whose sum is subjected to a carefully designed regularization procedure. This procedure involves an analytic derivation of certain ''''regularization parameters'' by means of a local analysis of the Green's function. This manuscript contains the following main parts: (1) Introduction of the mode sum scheme as applied to the gravitational case. (2) Two simple cases studied: the test case of a static particle in flat spacetime, and the case of a particle at a turning point of a radial geodesic in Schwarzschild spacetime. In both cases we derive all necessary regularization parameters. (3) An Analytic foundation is set for applying the scheme in more general cases. (In this paper, the mode sum scheme is formulated within the harmonic gauge. The implementation of the scheme in other gauges shall be discussed in a separate, forthcoming paper.)
2001
Article
http://edoc.mpg.de/2746
Physical Review D, v.64, 084021 (2001)
en
oai:edoc.mpg.de:27482009-03-206:83
Initial data for stationary spacetimes near spacelike infinity
Dain, Sergio
notspecified
We study Cauchy initial data for asymptotically flat, stationary vacuum spacetimes near spacelike infinity. The fall-off behaviour of the intrinsic metric and the extrinsic curvature is characterized. We prove that they have an analytic expansion in powers of a radial coordinate. The coefficients of the expansion are analytic functions of the angles. This result allow us to fill a gap in the proof found in the literature of the statement that all asymptotically flat, vacuum stationary spacetimes admit an analytic compactification at null infinity. Stationary initial data are physically important and highly non-trivial examples of a large class of data with similar regularity properties at spacelike infinity, namely, initial data for which the metric and the extrinsic curvature have asymptotic expansion in terms of powers of a radial coordinate. We isolate the property of the stationary data which is responsible for this kind of expansion.
2001
Article
http://edoc.mpg.de/2748
Classical and Quantum Gravity, v.18, 4329-4338 (2001)
en
oai:edoc.mpg.de:27492009-03-166:82
Gravitational self force and gauge transformations
Barack, Leor
Ori, Amos
notspecified
We explore how the gravitational self force (or ''''radiation reaction'' force), acting on a pointlike test particle in curved spacetime, is modified in a gauge transformation. We derive the general transformation law, describing the change in the self force in terms of the infinitesimal displacement vector associated with the gauge transformation. Based on this transformation law, we extend the regularization prescription by Mino et al. and Quinn and Wald (originally formulated within the harmonic gauge) to an arbitrary gauge. Then we extend the method of mode-sum regularization (which provides a practical means for calculating the regularized self force and was recently applied to the harmonic-gauge gravitational self force) to an arbitrary gauge. We find that the regularization parameters involved in this method are gauge-independent. We also explore the gauge transformation of the self force from the harmonic gauge to the Regge-Wheeler gauge and to the radiation gauge, focusing attention on the regularity of these gauge transformations. We conclude that the transformation of the self force to the Regge-Wheeler gauge in Schwarzschild spacetime is regular for radial orbits and irregular otherwise, whereas the transformation to the radiation gauge is irregular for all orbits.
2001
Article
http://edoc.mpg.de/2749
Physical Review D, v.64, 124003 (2001)
en
oai:edoc.mpg.de:27502009-04-026:84
On spacetime supersymmetry and string duality in nine dimensions
Abou-Zeid, Mohab
Nicolai, Hermann
notspecified
N = 2 extended space-time supersymmetry in nine dimensions implies that the BPS states corresponding to momentum and winding of either of the type-II superstrings compactified on S1 transform as inequivalent supermultiplets. This fact can be checked using world-sheet techniques, and provides the physical basis for the connection between IIA superstring theory compactified on a circle of radius R and IIB theory compactified on a circle of radius 1/R. Aspects of the duality between M-theory compactified on T2 and IIB theory compactified on S1 follow from the structure of N = 2, D = 9 supergravity. The coupling of N = 2, D = 9 supergravity to the BPS states is also discussed.
2000
Article
http://edoc.mpg.de/2750
urn:ISSN:0920-5632
info:doi/10.1016/S0920-5632(00)00765-9
Nuclear Physics B, v.88, 168-174 (2000)
en
oai:edoc.mpg.de:27532009-03-316:84
Colliding String Waves and Duality
Das, Ashok
Maharana, Jnanadeva
Melikyan, Arsen
notspecified
The collision of plane waves corresponding to massless states of closed string is considered in D-dimensional spaceŻtime. The reduced tree level effective action is known to be manifestly O(d,d) invariant, d being the number of transverse spatial dimensions in the collision process. We adopt a coset space reformulation of the effective two-dimensional theory and discuss the relation of this process with classical integrable systems in two dimensions in the presence of gravity. We show how it is possible to generate new backgrounds for the scattering process, from known background solutions to the equations of motion, in the coset reformulation. We present explicit calculations for the case of four spaceŻtime dimensions as an illustrative example.
2001
Article
http://edoc.mpg.de/2753
Physics Letters B, v.518, 306-314 (2001)
en
oai:edoc.mpg.de:27542009-03-206:83
Gravitational lensing in spherically symmetric static spacetimes with centrifugal force reversal
Hasse, Wolfgang
Perlick, Volker
notspecified
In Schwarzschild spacetime the value r = 3m of the radius coordinate is characterized by three different properties: (a) there is a ?light sphere,? (b) there is ?centrifugal force reversal,? (c) it is the upper limiting radius for a non-transparent Schwarzschild source to act as a gravitational lens that produces infinitely many images. In this paper we prove a theorem to the effect that these three properties are intimately related in any spherically symmetric static spacetime. We illustrate the general results with some examples including black-hole spacetimes and Morris-Thorne wormholes.
2002
Article
http://edoc.mpg.de/2754
General Relativity and Gravitation, v.34, 415-433 (2002)
en
oai:edoc.mpg.de:27552009-03-316:84
Open Strings in Simple Current Orbifolds
Matsubara, Keizo
Schomerus, Volker
Smedbäck, Mikael
notspecified
We study A(b)(a) branes and open strings in a large class of orbifold backgrounds using microscopic techniques of boundary conformal field theory. In particular, we obtain factorizing operator product expansions of open string vertex operators for such branes. Applications include branes in Z(2) orbifolds of the SU(2) WZW model and in the D-series of unitary minimal models considered previously by Runkel.
2002
Article
http://edoc.mpg.de/2755
Nuclear Physics B, v.626, 53-72 (2002)
en
oai:edoc.mpg.de:27562009-03-166:82
On the stability of the Kerr metric
Beyer, Horst R.
notspecified
The reduced (in the angular coordinate phi) wave equation and Klein-Gordon equation are considered on a Kerr background and in the framework of C-0-semigroup theory. Each equation is shown to have a well-posed initial value problem, i.e., to have a unique solution depending continuously on the data. Further, it is shown that the spectrum of the semigroup's generator coincides with the spectrum of an operator polynomial whose coefficients can be read off from the equation. In this way the problem of deciding stability is reduced to a spectral problem and a mathematical basis is provided for mode considerations. For the wave equation it is shown that the resolvent of the semigroup's generator and the corresponding Green's functions can be computed using spheroidal functions. It is to be expected that, analogous to the case of a Schwarzschild background, the quasinormal frequencies of the Kerr black hole appear as resonances, i.e., poles of the analytic continuation of this resolvent. Finally, stability of the solutions of the reduced Klein-Gordon equation is proven for large enough masses.
2001
Article
http://edoc.mpg.de/2756
Communications in Mathematical Physics, v.221, 659-676 (2001)
en
oai:edoc.mpg.de:27572009-05-286:84
Two Loops to Two Loops in N=4 Supersymmetric Yang-Mills Theory
Plefka, Jan
Staudacher, Matthias
notspecified
We present a full two-loop (g6) perturbative field theoretic calculation of the expectation value of two circular Maldacena-Wilson loops in D = 4 = 4 supersymmetric U(N) gauge theory. It is demonstrated that, after taking into account very subtle cancellations of bulk and boundary divergences, the result is completely finite without any renormalization. As opposed to previous lower order calculations existing in the literature, internal vertex diagrams no longer cancel identically and lead to subleading corrections to the dominant ladder diagrams. Taking limits, we proceed to extract the two-loop static potential corresponding to two infinite anti-parallel lines. Our result gives some evidence that the existing strong-coupling calculations using the AdS/CFT conjecture might sum up the full set of large N planar Feynman diagrams.
2001
Article
http://edoc.mpg.de/2757
Journal of High Energy Physics, v.09 (2001)
en
oai:edoc.mpg.de:27582009-03-316:84
On D0-branes in Gepner models
Scheidegger, Emanuel
notspecified
We show why and when D0-branes at the Gepner point of Calabi-Yau manifolds given as Fermat hypersurfaces exist.
2002
Article
http://edoc.mpg.de/2758
Journal of High Energy Physics, v.08, 001 (2002)
en
oai:edoc.mpg.de:27592009-03-206:83
Fuchsian analysis of S^2xS^1 and S^3 Gowdy spacetimes
Stahl, Fredrik
notspecified
The Gowdy spacetimes are vacuum solutions of the Einstein equations with two commuting Killing vectors having compact spacelike orbits with T3, S2 × S1 or S3 topology. In the case of T3 topology, Kichenassamy and Rendall have found a family of singular solutions which are asymptotically velocity dominated by construction. In the case when the velocity is between 0 and 1, the solutions depend on the maximal number of free functions. We consider the similar case with S2 × S1 or S3 topology, where the main complication is the presence of symmetry axes. The results for T3 may be applied locally except at the axes, where one of the Killing vectors degenerates. We use Fuchsian techniques to show the existence of singular solutions similar to the T3 case. We first solve the analytic case and then generalize to the smooth case by approximating smooth data with a sequence of analytic data. However, for the metric to be smooth at the axes, the velocity must be -1 or 3 there, which is outside the range where the constructed solutions depend on the full number of free functions. A plausible explanation is that in general a spiky feature may develop at the axis, a situation which is unsuitable for a direct treatment by Fuchsian methods.
2002
Article
http://edoc.mpg.de/2759
Classical and Quantum Gravity, v.19, 4483-4504 (2002)
en
oai:edoc.mpg.de:27602009-03-206:83
Global Prescribed Mean Curvature foliations in cosmological spacetimes I
Henkel, Oliver
notspecified
This work investigates some global questions about cosmological space-times with two-dimensional spherical, plane, and hyperbolic symmetry containing "well-behaved" matter. The result is that these space-times admit a global foliation by prescribed mean curvature surfaces, which extends at least toward a crushing singularity. The time function of the foliation is geometrically defined and unique up to the choice of an initial Cauchy surface. This work generalizes a similar analysis on constant mean curvature foliations and avoids the topological obstructions arising from the existence problem. (C) 2002 American Institute of Physics.
2002
Article
http://edoc.mpg.de/2760
Journal of Mathematical Physics, v.43, 2439-2465 (2002)
en
oai:edoc.mpg.de:27612009-03-206:83
Global Prescribed Mean Curvature foliations in cosmological spacetimes II
Henkel, Oliver
notspecified
This paper is devoted to the investigation of global properties of prescribed mean curvature (PMC) foliations in cosmological space-times with local U(1)xU(1) symmetry and matter described by the Vlasov equation. It turns out that these space-times admit a global foliation by PMC surfaces as well, but the techniques to achieve this goal are more complex than in the cases considered in Paper I [Henkel (2002)]
2002
Article
http://edoc.mpg.de/2761
Journal of Mathematical Physics, v.43, 2466-2485 (2002)
en
oai:edoc.mpg.de:27622009-03-206:83
Schwarzschild horizon and the gravitational redshift formula
Malec, Edward
notspecified
The gravitational redshift formula is usually derived in the geometric optics approximation. In this paper we consider an exact formulation of the problem in the Schwarzschild spacetime, with the intention of clarifying under what conditions this redshift law is valid. It is shown that in the case of shocks, the radial component of the Poynting vector can scale according to the redshift formula, under a suitable condition. If that condition is not satisfied, then the effect of backscattering can lead to significant modifications. The results obtained imply that the energy flux of the short wavelength radiation obeys the standard gravitational redshift formula while the energy flux of long waves can scale differently, with redshifts being dependent on the frequency.
2002
Article
http://edoc.mpg.de/2762
Classical and Quantum Gravity, v.19, 571-577 (2002)
en
oai:edoc.mpg.de:27632009-03-316:84
Dirichlet Branes on Orientifolds
Quiroz, N.
Stefanski, Bogdan
notspecified
We consider the classification of BPS and non-BPS D-branes in orientifold models. In particular we construct all stable BPS and non-BPS D-branes in the Gimon-Polchinski (GP) and Dabholkar-Park-Blum-Zaffaroni (DPBZ) orientifolds and determine their stability regions in moduli space as well as decay products. We find several kinds of integrally and torsion charged non-BPS D-branes. Certain of these are found to have projective representations of the orientifold×GSO group on the Chan-Paton factors. It is found that the GP orientifold is not described by equivariant orthogonal K-theory as may have been at first expected. Instead a twisted version of this K-theory is expected to be relevant.
2002
Article
http://edoc.mpg.de/2763
Physical Review D, v.66 (2002)
en
oai:edoc.mpg.de:27642009-03-206:83
Accelerated sources in de Sitter spacetime and the insufficiency of retarded fields
Bicak, Jiri
Krtous, Pavel
notspecified
The scalar and electromagnetic fields produced by the geodesic and uniformly accelerated discrete charges in de Sitter spacetime are constructed by employing the conformal relation between de Sitter and Minkowski space. Special attention is paid to new effects arising in spacetimes which, like de Sitter space, have spacelike conformal infinities. Under the presence of particle and event horizons, purely retarded fields (appropriately defined) become necessarily singular or even cannot be constructed at the "creation light cones"?future light cones of the "points" at which the sources "enter" the universe. We construct smooth (outside the sources) fields involving both retarded and advanced effects, and analyze the fields in detail in case of (i) scalar monopoles, (ii) electromagnetic monopoles, and (iii) electromagnetic rigid and geodesic dipoles.
2001
Article
http://edoc.mpg.de/2764
Physical Review D, v.64, 124020 (2001)
oai:edoc.mpg.de:27652009-03-166:82
Isometric embeddings of black hole horizons in three-dimensional flat space
Bondarescu, Mihai
Alcubierre, Miguel
Seidel, Edward
notspecified
The geometry of a two-dimensional surface in a curved space can be most easily visualized by using an isometric embedding in flat three-dimensional space. Here we present a new method for embedding surfaces with spherical topology in flat space when such an embedding exists. Our method is based on expanding the surface in spherical harmonics and minimizing the differences between the metric on the original surface and on the trial surface in the space of the expansion coefficients. We have applied this method to study the geometry of black-hole horizons in the presence of strong, non-axisymmetric, gravitational waves (Brill waves). We have noted that, in many cases, although the metric of the horizon seems to have large deviations from axisymmetry, the intrinsic geometry of the horizon is almost axisymmetric. The origin of the large apparent non-axisymmetry of the metric is the deformation of the coordinate system in which the metric was computed.
2002
Article
http://edoc.mpg.de/2765
Classical and Quantum Gravity, v.19, 375-391 (2002)
en
oai:edoc.mpg.de:27662009-03-316:84
A Lorentzian Cure for Euclidean Troubles
Ambjörn, Jan
Dasgupta, Arundhati
Jurkiewicz, Jerzy
Loll, Renate
notspecified
There is strong evidence coming from Lorentzian dynamical triangulations that the unboundedness of the gravitational action is no obstacle to the construction of a well-defined non-perturbative path integral. In a continuum approach, a similar suppression of the conformal divergence comes about as the result of a non-trivial path-integral measure.
2002
Article
http://edoc.mpg.de/2766
Nuclear Physics B Proc. Suppl., v.106, 977-979 (2002)
en
oai:edoc.mpg.de:27672009-03-316:84
Boundary Liouville Field theory : boundary three point function
Ponsot, Benedicte
Teschner, Jörg
notspecified
Liouville field theory is considered on domains with conformally invariant boundary conditions. We present an explicit expression for the three-point function of boundary fields in terms of the fusion coefficients which determine the monodromy properties of the conformal blocks.
2002
Article
http://edoc.mpg.de/2767
Nuclear Physics B, v.622, 309-327 (2002)
en
oai:edoc.mpg.de:27682009-03-166:82
Effect of hyperon bulk viscosity on neutron-star r-modes
Lindblom, Lee
Owen, Benjamin J.
notspecified
Neutron stars are expected to contain a significant number of hyperons in addition to protons and neutrons in the highest density portions of their cores. Following the work of Jones, we calculate the coefficient of bulk viscosity due to nonleptonic weak interactions involving hyperons in neutron-star cores, including new relativistic and superfluid effects. We evaluate the influence of this new bulk viscosity on the gravitational radiation driven instability in the r-modes. We find that the instability is completely suppressed in stars with cores cooler than a few times 109 K, but that stars rotating more rapidly than 10?30% of maximum are unstable for temperatures around 1010 K. Since neutron-star cores are expected to cool to a few times 109 K within seconds (much shorter than the r-mode instability growth time) due to direct Urca processes, we conclude that the gravitational radiation instability will be suppressed in young neutron stars before it can significantly change the angular momentum of the star.
2002
Article
http://edoc.mpg.de/2768
Physical Review D, v.65 (2002)
en
oai:edoc.mpg.de:27692009-03-166:82
Calculating the gravitational self force in Schwarzschild spacetime
Barack, Leor
Mino, Yasushi
Nakano, Hiroyuki
Ori, Amos
Sasaki, Misao
notspecified
We present a practical method for calculating the local gravitational self-force (often called "radiation-reaction force") for a pointlike particle orbiting a Schwarzschild black hole. This is an implementation of the method of mode-sum regularization, in which one first calculates the (finite) contribution to the force due to each individual multipole mode of the perturbation, and then applies a certain regularization procedure to the mode sum. Here we give the values of all the "regularization parameters" required for implementing this regularization procedure, for any geodesic orbit in Schwarzschild spacetime
2002
Article
http://edoc.mpg.de/2769
Physical Review Letters, v.88 (2002)
en
oai:edoc.mpg.de:27702009-03-316:84
Branching rules of semi-simple Lie algebras using affine extensions
Quella, Thomas
notspecified
We present a closed formula for the branching coefficients of an embedding [fraktur p] [hookrightarrow] [fraktur g] of two finite-dimensional semi-simple Lie algebras. The formula is based on the untwisted affine extension of [fraktur p] . It leads to an alternative proof of a simple algorithm for the computation of branching rules, which is an analogue of the Racah-Speiser algorithm for tensor products. We present some simple applications and describe how integral representations for branching coefficients can be obtained. In the last part, we comment on the relation of our approach to the theory of NIM-reps of the fusion ring in WZW models with chiral algebra [{mathfrak g}}_k] . In fact, it turns out that for these models each embedding [fraktur p] [hookrightarrow] [fraktur g] induces a NIM-rep at level k [rightarrow] [infty] . In cases where these NIM-reps can be extended to finite level, we obtain a Verlinde-like formula for branching coefficients. Reviewing this question, we propose a solution to a puzzle which remained open in related work by Alekseev, Fredenhagen, Quella and Schomerus.
2002
Article
http://edoc.mpg.de/2770
Journal of Physics A, v.35, 3743-3753 (2002)
en
oai:edoc.mpg.de:27712009-03-316:84
D-branes in coset models
Fredenhagen, Stefan
Schomerus, Volker
notspecified
The analysis of D-branes in coset models G/H provides a natural extension of recent studies on branes in WZW-theory and it has various interesting applications to physically relevant models. In this work we develop a reduction procedure that allows to construct the non-commutative gauge theories which govern the dynamics of branes in G/H. We obtain a large class of solutions and interpret the associated condensation processes geometrically. The latter are used to propose conservation laws for the dynamics of branes in coset models at large level k. In super-symmetric theories, conserved charges are argued to take their values in the representation ring of the denominator theory. Finally, we apply the general results to study boundary fixed points in two examples, namely for parafermions and minimal models.
2002
Article
http://edoc.mpg.de/2771
Journal of High Energy Physics, v.02 (2002)
en
oai:edoc.mpg.de:27722009-03-206:83
Initial data for fluid bodies in general relativity
Dain, Sergio
Nagy, Gabriel
notspecified
We show that there exist asymptotically flat almost-smooth initial data for the Einstein?perfect-fluid equation that represent an isolated liquid-type body. By liquid-type body we mean that the fluid energy density has compact support and takes a strictly positive constant value at its boundary. By almost-smooth we mean that all initial data fields are smooth everywhere on the initial hypersurface except at the body boundary, where tangential derivatives of any order are continuous at that boundary.
2002
Article
http://edoc.mpg.de/2772
Physical Review D, v.65, 084020 (2002)
en
oai:edoc.mpg.de:27732009-03-316:84
Implications of Superconformal Symmetry for Interacting (2,0) Tensor Multiplets
Arutyunov, Gleb
Sokatchev, E.
notspecified
We study the structure of the four-point correlation function of the lowest-dimension 1/2 BPS operators (stress-tensor multiplets) in the (2,0) six-dimensional theory. We first discuss the superconformal Ward identities and the group-theoretical restrictions on the corresponding OPE. We show that the general solution of the Ward identities is expressed in terms of a single function of the two conformal cross-ratios ("prepotential"). Using the maximally extended gauged seven-dimensional supergravity, we then compute the four-point amplitude in the supergravity approximation and identify the corresponding prepotential. We analyze the leading terms in the OPE by performing a conformal partial wave expansion and show that they are in agreement with the non-renormalization theorems following from representation theory. The investigation of the (2,0) theory is carried out in close parallel with the familiar four-dimensional [View Image] super-Yang?Mills theory
2002
Article
http://edoc.mpg.de/2773
Nuclear Physics B, v.635, 3-32 (2002)
en
oai:edoc.mpg.de:27742009-03-316:84
Limiting Geometries of Two Circular Maldacena-Wilson Loop Operators
Arutyunov, Gleb
Plefka, Jan
Staudacher, Matthias
notspecified
We further analyze a recent perturbative two-loop calculation of the expectation value of two axi-symmetric circular Maldacena-Wilson loops in [Script N] = 4 gauge theory. Firstly, it is demonstrated how to adapt the previous calculation of anti-symmetrically oriented circles to the symmetric case. By shrinking one of the circles to zero size we then explicitly work out the first few terms of the local operator expansion of the loop. Our calculations explicitly demonstrate that circular Maldacena-Wilson loops are non-BPS observables precisely due to the appearance of unprotected local operators. The latter receive anomalous scaling dimensions from non-ladder diagrams. Finally, we present new insights into a recent conjecture claiming that coincident circular Maldacena-Wilson loops are described by a gaussian matrix model. We report on a novel, supporting two-loop test, but also explain and illustrate why the existing arguments in favor of the conjecture are flawed.
2001
Article
http://edoc.mpg.de/2774
Journal of High Energy Physics, v.12, 014 (2001)
en
oai:edoc.mpg.de:27752009-03-206:83
A New Tradition between Discrete and Contiuous Self-Similarity in Critical Gravitational Collapse
Lechner, Christiane
Thornburg, Jonathan
Husa, Sascha
Aichelburg, Peter C.
notspecified
We analyze a bifurcation phenomenon associated with critical gravitational collapse in a family of self-gravitating SU(2) sigma models. As the dimensionless coupling constant decreases, the critical solution changes from discretely self-similar (DSS) to continuously self-similar (CSS). Numerical results provide evidence for a bifurcation which is analogous to a heteroclinic loop bifurcation in dynamical systems, where two fixed points (CSS) collide with a limit cycle (DSS) in phase space as the coupling constant tends to a critical value.
2002
Article
http://edoc.mpg.de/2775
Physical Review D, v.65 (2002)
en
oai:edoc.mpg.de:27762009-03-206:83
Book Review : The Universe. Visions and Perspectives
Winicour, Jeffrey
notspecified
I review the collection of essays which the editors Naresh Dadich and Ajit Kembhavi have assembled as a festschrift to honor Jayant Narlikar.
2002
Article
http://edoc.mpg.de/2776
General Relativity and Gravitation, v.34, 1327-1329 (2002)
en
oai:edoc.mpg.de:27772009-03-206:83
Cosmological models and centre manifold theory
Rendall, Alan D.
notspecified
Centre manifold theory is applied to some dynamical systems arising from spatially homogeneous cosmological models. Detailed information is obtained concerning the late-time behaviour of solutions of the Einstein equations of Bianchi type III with collisionless matter. In addition some statements in the literature on solutions of the Einstein equations coupled to a massive scalar field are proved rigorously.
2002
Article
http://edoc.mpg.de/2777
General Relativity and Gravitation, v.34, 1277-1294 (2002)
en
oai:edoc.mpg.de:27782009-03-316:84
Fivebranes Wrapped on SLAG Three-Cycles and Related Geometry
Gauntlett, Jerome P.
Kim, Nakwoo
Martelli, Dario
Waldram, Daniel
notspecified
We construct ten-dimensional supergravity solutions corresponding to the near horizon limit of IIB fivebranes wrapping special lagrangian three-cycles of constant curvature. The case of branes wrapping a three-sphere provides a gravity dual of pure [Script N] = 2 super--Yang-Mills theory in D = 3. The non-trivial part of the solutions are seven manifolds that admit two G2 structures each of which is covariantly constant with respect to a different connection with torsion. We derive a formula for the generalised calibration for this general class of solutions. We discuss analogous aspects of the geometry that arises when fivebranes wrap other supersymmetric cycles which lead to Spin(7) and SU(N) structures. In some cases there are two covariantly constant structures and in others one.
2001
Article
http://edoc.mpg.de/2778
Journal of High Energy Physics, v.11, 018 (2001)
en
oai:edoc.mpg.de:27792009-03-316:84
Branes in the Euclidean AdS_3
Ponsot, Benedicte
Schomerus, Volker
Teschner, Jörg
notspecified
In this work we propose an exact microscopic description of maximally symmetric branes in a euclidean AdS3 background. As shown by Bachas and Petropoulos, the most important such branes are localized along a euclidean AdS2 [subset] AdS3. We provide explicit formulas for the coupling of closed strings to such branes (boundary states) and for the spectral density of open strings. The latter is computed in two different ways first in terms of the open string reflection amplitude and then also from the boundary states by world-sheet duality. This gives rise to an important Cardy type consistency check. All the results are compared in detail with the geometrical picture. We also discuss a second class of branes with spherical symmetry and finally comment on some implications for D-branes in a 2D back hole geometry
2002
Article
http://edoc.mpg.de/2779
Journal of High Energy Physics, v.02 (2002)
en
oai:edoc.mpg.de:27802009-03-206:83
Retarded radiation from colliding black holes in the close limit
Husa, Sascha
Zlochower, Yosef
Gomez, Roberto
Winicour, Jeffrey
notspecified
We use null hypersurface techniques in a new approach to calculate the retarded waveform from a binary black hole merger in the close approximation. The process of removing ingoing radiation from the system leads to two notable features in the shape of the close approximation waveform for a head-on collision of black holes: (i) an initial quasinormal ringup and (ii) weak sensitivity to the parameter controlling the collision velocity. Feature (ii) is unexpected and has the potential importance of enabling the design of an efficient template for extracting the gravitational wave signal from the noise.
2002
Article
http://edoc.mpg.de/2780
Physical Review D, v.65 (2002)
en
oai:edoc.mpg.de:27812009-03-206:83
Simplified models of electromagnetic and gravitational radiation damping
Kunze, Markus
Rendall, Alan D.
notspecified
In previous work the authors have analysed the global properties of an approximate model of radiation damping for charged particles. This work is put into context and related to the original motivation of understanding approximations used in the study of gravitational radiation damping. We examine to what extent the results obtained previously depend on the particular model chosen. Comparisons are made with other models for gravitational and electromagnetic fields. The relation of the kinetic model for which theorems were proved to certain many-particle models with radiation damping is exhibited
2001
Article
http://edoc.mpg.de/2781
Classical and Quantum Gravity, v.18, 3573-3587 (2001)
en
oai:edoc.mpg.de:27822009-04-026:84
A non-perturbative Lorentzian path integral for gravity
Ambjörn, Jan
Jurkiewicz, Jerzy
Loll, Renate
notspecified
We construct a well-defined regularized path integral for Lorentzian quantum gravity in terms of dynamically triangulated causal space-times. Each Lorentzian geometry and its action have a unique Wick rotation to the Euclidean sector. All space-time histories possess a distinguished notion of a discrete proper time and, for finite lattice volume, the associated transfer matrix is self-adjoint, bounded, and strictly positive. The degenerate geometric phases found in dynamically triangulated Euclidean gravity are not present.
2000
Article
http://edoc.mpg.de/2782
Physical Review Letters, v.85, 924-927 (2000)
en
oai:edoc.mpg.de:27832009-04-026:84
Supersymmetric effective action of Matrix theory
Nicolai, Hermann
Plefka, Jan
notspecified
We present a simple derivation of the supersymmetric one-loop effective action of SU(2) Matrix theory by expressing it in a compact exponential form whose invariance under supersymmetry transformations is obvious. This result clarifies the one-loop exactness of the leading (v2)2 interactions and the absence of non-perturbative corrections.
2000
Article
http://edoc.mpg.de/2783
urn:ISSN:0370-2693
info:doi/10.1016/S0370-2693(00)00210-0
Physics Letters B, v.477, 309-312 (2000)
en
oai:edoc.mpg.de:27852009-05-276:82
Keplerian frequencies and innermost stable circular orbits of rapidly rotating strange stars
Stergioulas, Nikolaos
Kluzniak, W.
Bulik, T.
notspecified
It has been suggested that the frequency in the co-rotating innermost stable circular orbit (ISCO) about a compact stellar remnant can be determined through X-ray observations of low-mass X-ray binaries, and that its value can be used to constrain the equation of state of ultradense matter.
Upon constructing numerical models of rapidly rotating strange (quark) stars in general relativity, we find that for stars rotating at the equatorial mass-shedding limit, the ISCO is indeed above the stellar surface, for a wide range of central energy densities at a height equal to 11% of the circumferential stellar radius, which scales inversely with the square root of the energy density, of self-bound quark matter at zero presure. In contrast to static stars, the ISCO frequencies of rapidly rotating strange stars can be as low as 0.9 kHz for a 1.3 solar mass strange star. Hence, the presence of strange stars in low-mass X-ray binaries cannot be excluded on the basis of the currently observed frequencies of kHz QPOs, such as the cut-off frequency of 1066 Hz in 4U 1820-30.
1999
Article
http://edoc.mpg.de/2785
Astronomy and Astrophysics, v.352, L116-L120 (1999)
en
oai:edoc.mpg.de:27862009-03-206:83
Quiscent cosmological singularities
Andersson, Lars
Rendall, Alan D.
notspecified
The most detailed existing proposal for the structure of spacetime singularities originates in the work of Belinskii, Khalatnikov and Lifshitz. We show rigorously the correctness of this proposal in the case of analytic solutions of the Einstein equations coupled to a scalar field or stiff fluid. More specifically, we prove the existence of a family of spacetimes depending on the same number of free functions as the general solution which have the asymptotics suggested by the Belinskii-Khalatnikov-Lifshitz proposal near their singularities. In these spacetimes a neighbourhood of the singularity can be covered by a Gaussian coordinate system in which the singularity is simultaneous and the evolution at different spatial points decouples.
2001
Article
http://edoc.mpg.de/2786
Communications in Mathematical Physics, v.218, 479-511 (2001)
en
oai:edoc.mpg.de:27872009-03-206:83
Local and global existence theorems for the Einstein equations
Rendall, Alan D.
notspecified
This article is a guide to the literature on existence theorems for the Einstein equations which also draws attention to open problems in the field. The local in time Cauchy problem, which is relatively well understood, is treated first. Next global results for solutions with symmetry are discussed. A selection of results from Newtonian theory and special relativity which offer useful comparisons is presented. This is followed by a survey of global results in the case of small data and results on constructing spacetimes with given singularity structure. The article ends with some miscellaneous topics connected with the main theme.
2000
Article
http://edoc.mpg.de/2787
Living Reviews in Relativity, v.3 (2000)
en
oai:edoc.mpg.de:27892009-04-026:84
An exceptional geometry for d=11 supergravity?
Koepsell, Kilian
Nicolai, Hermann
Samtleben, Henning
notspecified
We analyse the algebraic constraints of the generalized vielbein in SO(1,2)×SO(16) invariant d = 11 supergravity, and show that the bosonic degrees of freedom of d = 11 supergravity, which become the physical ones upon reduction to d = 3, can be assembled into an E8(8)-valued vielbein already in 11 dimensions. A crucial role in the construction is played by the maximal nilpotent commuting subalgebra of E8(8), of dimension 36, suggesting a partial unification of general coordinate and tensor gauge transformations.
2000
Article
http://edoc.mpg.de/2789
urn:ISSN:0264-9381
info:doi/10.1088/0264-9381/17/18/308
Classical and Quantum Gravity, v.17, 3689-3702 (2000)
en
oai:edoc.mpg.de:27902009-03-166:82
Adaptive filtering techniques for gravitational wave interferometric data: Removing long-term sinusoidal disturbances and oscillatory transients
Chassande-Mottin, Eric
Dhurandhar, Sanjeev
notspecified
It is known by the experience gained from the gravitational wave detector prototypes that the interferometric output signal will be corrupted by a significant amount of non-Gaussian noise, a large part of it being essentially composed of long-term sinusoids with a slowly varying envelope (such as violin resonances in the suspensions, or main power harmonics) and short-term ringdown noise (which may emanate from servo control systems, electronics in a nonlinear state, etc.). Since non-Gaussian noise components make the detection and estimation of the gravitational wave signature more difficult, a denoising algorithm based on adaptive filtering techniques (LMS methods) is proposed to separate and extract them from the stationary and Gaussian background noise. The strength of the method is that it does not require any precise model on the observed data: the signals are distinguished on the basis of their autocorrelation time. We believe that the robustness and simplicity of this method make it useful for data preparation and for the understanding of the first interferometric data. We present the detailed structure of the algorithm and its application to both simulated data and real data from the LIGO 40 m prototype.
2001
Article
http://edoc.mpg.de/2790
Physical Review D, v.63, 042004 (2001)
en
oai:edoc.mpg.de:27912009-04-066:83
Dual Group Actions on C*-Algebras and Their Description by Hilbert Extensions
Baumgärtel, Hellmut
Lledo, Fernando
notspecified
Given a C*-algebra $A$, a discrete abelian group $X$ and a homomorphism $Theta: X o$ Out$A$ defining the dual action group $Gammasubset$ aut$A$, the paper contains results on existence and characterization of Hilbert ${A,Gamma}$, where the action is given by $hat{X}$. They are stated at the (abstract) C*-level and can therefore be considered as a refinement of the extension results given for von Neumann algebras for example by Jones [Mem.Am.Math.Soc. 28 Nr 237 (1980)] or Sutherland [Publ.Res.Inst.Math.Sci. 16 (1980) 135]. A Hilbert extension exists iff there is a generalized 2-cocycle. These results generalize those in [Commun.Math.Phys. 15 (1969) 173], which are formulated in the context of superselection theory, where it is assumed that the algebra $A$ has a trivial center, i.e. $Z=C1$. In particular the well-known ''''outer characterization'' of the second cohomology $H^2(X,{cal U}(Z),alpha_X)$ can be reformulated: there is a bijection to the set of all $A$-module isomorphy classes of Hilbert extensions. Finally, a Hilbert space representation (due to Sutherland in the von Neumann case) is mentioned. The C*-norm of the Hilbert extension is expressed in terms of the norm of this representation and it is linked to the so-called regular representation appearing in superselection theory.
2002
Article
http://edoc.mpg.de/2791
Mathematische Nachrichten, v.239-240, 11-27 (2002)
en
oai:edoc.mpg.de:27922009-03-206:83
Conformal covariance of massless free nets
Lledo, Fernando
notspecified
In the present paper we review in a fibre bundle context the covariant and massless canonical representations of the Poincare' group as well as certain unitary representations of the conformal group (in 4 dimensions). We give a simplified proof of the well-known fact that massless canonical representations with discrete helicity extend to unitary and irreducible representations of the conformal group mentioned before. Further we give a simple new proof that massless free nets for any helicity value are covariant under the conformal group. Free nets are the result of a direct (i.e. independent of any explicit use of quantum fields) and natural way of constructing nets of abstract C*-algebras indexed by open and bounded regions in Minkowski space that satisfy standard axioms of local quantum physics. We also give a group theoretical interpretation of the embedding ${got I}$ that completely characterizes the free net: it reduces the (algebraically) reducible covariant representation in terms of the unitary canonical ones. Finally, as a consequence of the conformal covariance we also mention for these models some of the expected algebraic properties that are a direct consequence of the conformal covariance (essential duality, PCT--symmetry etc.).
2001
Article
http://edoc.mpg.de/2792
Reviews in Mathematical Physics, v.13, 1135-1161 (2001)
en
oai:edoc.mpg.de:27932009-03-166:82
Gravitational waves from black hole collisions via an eclectic approach
Baker, John G.
Brügmann, Bernd
Campanelli, Manuela
Lousto, Carlos O.
notspecified
We present the first results in a new program intended to make the best use of all available technologies to provide an effective understanding of waves from inspiralling black hole binaries in time to assist imminent observations. In particular, we address the problem of combining the close-limit approximation describing ringing black holes and full numerical relativity, required for essentially nonlinear interactions. We demonstrate the effectiveness of our approach using general methods for a model problem, the head-on collision of black holes. Our method allows a more direct physical understanding of these collisions indicating clearly when non-linear methods are important. The success of this method supports our expectation that this unified approach will be able to provide relevant results for black hole binaries in time to assist gravitational wave observations.
2000
Article
http://edoc.mpg.de/2793
Classical and Quantum Gravity, v.17, L149-L156 (2000)
en
oai:edoc.mpg.de:27942009-03-166:82
Making use of geometrical invariants in black hole collisions
Baker, John G.
Campanelli, Manuela
notspecified
We consider curvature invariants in the context of black hole collision simulations. In particular, we propose a simple and elegant combination of the Weyl invariants I and J, the speciality index [script S]. In the context of black hole perturbations [script S] provides a measure of the size of the distortions from an ideal Kerr black hole spacetime. Explicit calculations in well-known examples of axisymmetric black hole collisions demonstrate that this quantity may serve as a useful tool for predicting in which cases the close limit can provide an accurate estimate of the radiation wave form and energy. This makes [script S] particularly suited to studying the transition from nonlinear to linear dynamics and for an invariant interpretation of numerical results.
2000
Article
http://edoc.mpg.de/2794
Physical Review D, v.62, 127501 (2000)
en
oai:edoc.mpg.de:27952009-04-026:84
Vertex Operators for the Supermembrane
Dasgupta, Arundhati
Nicolai, Hermann
Plefka, Jan
notspecified
We derive the vertex operators that are expected to govern the emission of the massless d = 11 supermultiplet from the supermembrane in the light cone gauge. We demonstrate that they form a representation of the supersymmetry algebra and reduce to the type-IIA superstring vertex operators under double-dimensional reduction, as well as to the vertices of the d = 11 superparticle in the point-particle limit. As a byproduct, our results can be used to derive the corresponding vertex operators for matrix theory and to describe its linear coupling to an arbitrary d = 11 supergravity background. Possible applications are discussed.
2000
Article
http://edoc.mpg.de/2795
urn:ISSN:1126-6708
info:doi/10.1088/1126-6708/2000/05/007
Journal of High Energy Physics, v.05 (2000)
en
oai:edoc.mpg.de:27962009-03-166:82
Towards a Stabel Numerical Evolution of Strongly Gravitating Systems in General Relativity :The Conformal Treatments
Alcubierre, Miguel
Brügmann, Bernd
Dramlitsch, Thomas
Font, Jose A.
Papadopoulos, Philippos
Seidel, Edward
Stergioulas, Nikolaos
Takahashi, Ryoji
notspecified
We study the stability of three-dimensional numerical evolutions of the Einstein equations, comparing the standard ADM formulation to variations on a family of formulations that separate out the conformal and traceless parts of the system. We develop an implementation of the conformal-traceless (CT) approach that has improved stability properties in evolving weak and strong gravitational fields, and for both vacuum and spacetimes with active coupling to matter sources. Cases studied include weak and strong gravitational wave packets, black holes, boson stars and neutron stars. We show under what conditions the CT approach gives better results in 3D numerical evolutions compared to the ADM formulation. In particular, we show that our implementation of the CT approach gives more long term stable evolutions than ADM in all the cases studied, but is less accurate in the short term for the range of resolutions used in our 3D simulations. Š2000 The American Physical Society
2000
Article
http://edoc.mpg.de/2796
Physical Review D, v.62, 044034 (2000)
en
oai:edoc.mpg.de:27972009-04-026:84
Yang-Mills Integrals for Orthogonal, Symplectic and Exceptional Groups
Krauth, Werner
Staudacher, Matthias
notspecified
We apply numerical and analytic techniques to the study of YangŻ Mills integrals with orthogonal, symplectic and exceptional gauge symmetries. The main focus is on the supersymmetric integrals, which correspond essentially to the bulk part of the Witten index for susy quantum mechanical gauge theory. We evaluate these integrals for D=4 and group rank up to three, using Monte Carlo methods. Our results are at variance with previous findings. We further compute the integrals with the deformation technique of Moore, Nekrasov and Shatashvili, which we adapt to the groups under study. Excellent agreement with all our numerical calculations is obtained. We also discuss the convergence properties of the purely bosonic integrals.
2000
Article
http://edoc.mpg.de/2797
Nuclear Physics B, v.584, 641-655 (2000)
en
oai:edoc.mpg.de:27982009-03-206:83
Fuchsian analysis of singularities in Gowdy spacetimes beyond analyticity
Rendall, Alan D.
Fuchsian equations provide a way of constructing large classes of spacetimes whose singularities can be described in detail. In some of the applications of this technique only the analytic case could be handled up to now. This paper develops a method of removing the undesirable hypothesis of analyticity. This is applied to the specific case of the Gowdy spacetimes in order to show that analogues of the results known in the analytic case hold in the smooth case. As far as possible the likely strengths and weaknesses of the method, as applied to more general problems, are displayed.
2000
Article
http://edoc.mpg.de/2798
Classical and Quantum Gravity, v.17, 3305-3316 (2000)
en
oai:edoc.mpg.de:27992009-03-316:84
Quantum spin dynamics (QSD): VII. Symplectic structures and continuum lattice formulations of gauge field theories
Thiemann, Thomas
notspecified
Interesting nonlinear functions on the phase spaces of classical field theories can never be quantized immediately because the basic fields of the theory become operator-valued distributions. Therefore, one is usually forced to find a smeared substitute for such a function which corresponds to a regularization. The smeared functions define a new symplectic manifold of their own which is easy to quantize. Finally, one must remove the regulator and establish that the final operator, if it exists, has the correct classical limit.
In this paper we begin the investigation of these steps for diffeomorphism-invariant quantum field theories of connections. We introduce a (generalized) projective family of symplectic manifolds, coordinatized by the smeared fields, which is labelled by a pair consisting of a graph and another graph dual to it. We show that a subset of the corresponding projective limit can be identified with the symplectic manifold that one started from. Then we illustrate the programme outlined above by applying it to the Gauss constraint.
This paper also complements, as a side result, earlier work by Ashtekar, Corichi and Zapata who observed that certain operators are non-commuting on certain states, although the Poisson brackets between the corresponding classical functions vanish. These authors showed that this is not a contradiction provided that one refrains from a phase space quantization but rather applies a quantization based on the Lie algebra of vector fields on the configuration space of the theory. Here we show that one can provide a phase space quantization, that is, one can find other functions on the classical phase space which give rise to the same operators but whose Poisson algebra precisely mirrors the quantum commutator algebra.
The framework developed here is the classical cornerstone on which the semiclassical analysis in a new series of papers called ''gauge theory coherent states' is based.
2001
Article
http://edoc.mpg.de/2799
Classical and Quantum Gravity, v.18, 3293-3338 (2001)
en
oai:edoc.mpg.de:28002009-03-316:84
Gauge field theory coherent states (GCS): I. General properties
Thiemann, Thomas
notspecified
In this paper we outline a rather general construction of diffeomorphism covariant coherent states for quantum gauge theories. By this we mean states [psi] (A,E), labelled by a point (A,E) in the classical phase space, consisting of canonically conjugate pairs of connections A and electric fields E, respectively, such that: (a) they are eigenstates of a corresponding annihilation operator which is a generalization of A-iE smeared in a suitable way; (b) normal ordered polynomials of generalized annihilation and creation operators have the correct expectation value; (c) they saturate the Heisenberg uncertainty bound for the fluctuations of [hat A] , [hat E] ; and (d) they do not use any background structure for their definition, that is, they are diffeomorphism covariant.
This is the first paper in a series of articles entitled ''Gauge field theory coherent states (GCS)' which aims to connect non-perturbative quantum general relativity with the low-energy physics of the standard model. In particular, coherent states enable us for the first time to take into account quantum metrics which are excited everywhere in an asymptotically flat spacetime manifold as is needed for semiclassical considerations.
The formalism introduced in this paper is immediately applicable also to lattice gauge theory in the presence of a (Minkowski) background structure on a possibly infinite lattice.
2001
Article
http://edoc.mpg.de/2800
Classical and Quantum Gravity, v.18, 2025-2064 (2001)
oai:edoc.mpg.de:28012009-03-316:84
Gauge field theory coherent states (GCS): II. Peakedness properties
Thiemann, Thomas
Winkler, Oliver
notspecified
In this paper we apply the methods outlined in the previous paper of this series to the particular set of states obtained by choosing the complexifier to be a Laplace operator for each edge of a graph. The corresponding coherent state transform was introduced by Hall for one edge and generalized by Ashtekar, Lewandowski, Marolf, Mourăo and Thiemann to arbitrary, finite, piecewise-analytic graphs.
However, both of these works were incomplete with respect to the following two issues.
The focus was on the unitarity of the transform and left the properties of the corresponding coherent states themselves untouched.
While these states depend in some sense on complexified connections, it remained unclear what the complexification was in terms of the coordinates of the underlying real phase space.
In this paper we complement these results: first, we explicitly derive the complexification of the configuration space underlying these heat kernel coherent states and, secondly, prove that this family of states satisfies all the usual properties.
(i) Peakedness in the configuration, momentum and phase space (or Bargmann-Segal) representation.
(ii) Saturation of the unquenched Heisenberg uncertainty bound.
(iii) (Over)completeness.
These states therefore comprise a candidate family for the semiclassical analysis of canonical quantum gravity and quantum gauge theory coupled to quantum gravity. They also enable error-controlled approximations to difficult analytical calculations and therefore set a new starting point for numerical, semiclassical canonical quantum general relativity and gauge theory.
The text is supplemented by an appendix which contains extensive graphics in order to give a feeling for the so far unknown peakedness properties of the states constructed.
2001
Article
http://edoc.mpg.de/2801
Classical and Quantum Gravity, v.18, 2561-2636 (2001)
en
oai:edoc.mpg.de:28022009-03-316:84
Gauge field theory coherent states (GCS): III. Ehrenfest theorems
Thiemann, Thomas
Winkler, Oliver
notspecified
In the preceding paper of this series of articles we established peakedness properties of a family of coherent states that were introduced by Hall for any compact gauge group and were later generalized to gauge field theory by Ashtekar, Lewandowski, Marolf, Mourăo and Thiemann.
In this paper we establish the ''Ehrenfest property' of these states which are labelled by a point (A,E), a connection and an electric field, in the classical phase space. By this we mean that the expectation values of the elementary operators (and of their commutators divided by i [hbar] , respectively) in a coherent state labelled by the (A,E) are, to zeroth order in [hbar] , given by the values of the corresponding elementary functions (and of their Poisson brackets, respectively) at the point (A,E).
These results can be extended to all polynomials of elementary operators and to a certain non-polynomial function of the elementary operators associated with the volume operator of quantum general relativity. These findings are another step towards establishing that the infinitesimal quantum dynamics of quantum general relativity might, to lowest order in [hbar] , indeed be given by classical general relativity.
2001
Article
http://edoc.mpg.de/2802
Classical and Quantum Gravity, v.18, 4629-4681 (2001)
en
oai:edoc.mpg.de:28032009-03-316:84
Gauge field theory coherent states (GCS): IV. Infinite tensor product and thermodynamical limit
Thiemann, Thomas
Winkler, Oliver
notspecified
In the canonical approach to Lorentzian quantum general relativity in four spacetime dimensions an important step forward has been made by Ashtekar, Isham and Lewandowski some eight years ago through the introduction of a Hilbert space structure, which was later proved to be a faithful representation of the canonical commutation and adjointness relations of the quantum field algebra of diffeomorphism invariant gauge field theories by Ashtekar, Lewandowski, Marolf, Mourăo and Thiemann. This Hilbert space, together with its generalization due to Baez and Sawin, is appropriate for semi-classical quantum general relativity if the spacetime is spatially compact. In the spatially non-compact case, however, an extension of the Hilbert space is needed in order to approximate metrics that are macroscopically nowhere degenerate. For this purpose, in this paper we apply the theory of the infinite tensor product (ITP) of Hilbert Spaces, developed by von Neumann more than sixty years ago, to quantum general relativity. The cardinality of the number of tensor product factors can take the value of any possible Cantor aleph, making this mathematical theory well suited to our problem in which a Hilbert space is attached to each edge of an arbitrarily complicated, generally infinite graph. The new framework opens access to a new arsenal of techniques, appropriate to describe fascinating physics such as quantum topology change, semi-classical quantum gravity, effective low-energy physics etc from the universal point of view of the ITP. In particular, the study of photons and gravitons propagating on fluctuating quantum spacetimes should now be in reach.
2001
Article
http://edoc.mpg.de/2803
Classical and Quantum Gravity, v.18, 4997-5053 (2001)
en
oai:edoc.mpg.de:28042009-04-026:84
Currents and Superpotentials in classical gauge theories: II. Global aspects and the example of Affine gravity
Julia, Bernard
Silva, Sebastian
notspecified
The conserved charges associated with gauge symmetries are defined at a boundary component of spacetime because the corresponding Noether current can be rewritten on-shell as the divergence of a superpotential. However, the latter is afflicted by ambiguities. Regge and Teitelboim found a procedure to lift the arbitrariness in the Hamiltonian framework. An alternative covariant formula was proposed by one of us for an arbitrary variation of the superpotential, it depends only on the equations of motion and on the gauge symmetry under consideration. Here we emphasize that in order to compute the charges, it is enough to stay at a boundary of spacetime, without requiring any hypothesis about the bulk or about other boundary components, so one may speak of holographic charges. It is well known that the asymptotic symmetries
that lead to conserved charges are really defined at infinity, but the choice of boundary conditions and surface terms in the action and in the charges is usually determined
through integration by parts, whereas each component of the boundary should be considered separately. We treat the example of gravity (for any spacetime dimension, with
or without cosmological constant), formulated as an affine theory which is a natural generalization of the Palatini and Cartan-Weyl (vielbein) first-order formulations. We then
show that the superpotential associated with a Dirichlet boundary condition on the metric (the one needed to treat asymptotically flat or AdS spacetimes) is the one proposed
by Katz et al and not that of Komar. We finally discuss the KBL superpotential at null infinity.
2000
Article
http://edoc.mpg.de/2804
Classical and Quantum Gravity, v.17, 4733-4744 (2000)
en
oai:edoc.mpg.de:28052009-04-066:83
Dynamics of spatially homogeneous locally rotationally symmetric solutions of the Einstein-Vlasov equations
Rendall, Alan D.
Uggla, Claes
notspecified
The dynamics of the Einstein-Vlasov equations for a class of cosmological models with four Killing vectors is discussed in the case of massive particles. It is shown that in all models analysed the solutions with massive particles are asymptotic to solutions with massless particles at early times. It is also shown that in Bianchi types I and II the solutions with massive particles are asymptotic to dust solutions at late times. That Bianchi type III models are also asymptotic to dust solutions at late times is consistent with our results but is not established by them.
2000
Article
http://edoc.mpg.de/2805
Classical and Quantum Gravity, v.17, 4697-4714 (2000)
en
oai:edoc.mpg.de:28062009-03-166:82
Simple excision of a black hole in 3 + 1 numerical relativity
Alcubierre, Miguel
Brügmann, Bernd
notspecified
We describe a simple implementation of black hole excision in 3 + 1 numerical relativity. We apply this technique to a Schwarzschild black hole with
octant symmetry in Eddington-Finkelstein coordinates and show how one can obtain accurate, long-term stable numerical evolutions.
2001
Article
http://edoc.mpg.de/2806
Physical Review D, v.63 (2001)
en
oai:edoc.mpg.de:28072009-03-166:82
Effect of a neutron-star crust on the r-mode instability
Lindblom, Lee
Owen, Benjamin J.
Ushomirsky, Greg
notspecified
The presence of a viscous boundary layer under the solid crust of a neutron star dramatically increases the viscous damping rate of the fluid
r-modes. We improve previous estimates of this damping rate by including the effect of the Coriolis force on the boundary-layer eigenfunction and
by using more realistic neutron-star models. If the crust is assumed to be perfectly rigid, the gravitational radiation driven instability in the r-modes
is completely suppressed in neutron stars colder than about 1.5×108 K. Energy generation in the boundary layer will heat the star, and will even
melt the crust if the amplitude of the r-mode is large enough. We solve the heat equation explicitly (including the effects of thermal conduction and
neutrino emission) and find that the r-mode amplitude needed to melt the crust is alphac[approximate]5×103 for maximally rotating neutron stars.
If the r- mode saturates at an amplitude larger than alphac, the heat generated is sufficient to maintain the outer layers of the star in a mixed
fluid-solid state analogous to the pack ice on the fringes of the Arctic Ocean. We argue that in young, rapidly rotating neutron stars this effect
considerably delays the formation of the crust. By considering the dissipation in the ice flow, we show that the final spin frequency of stars with
r-mode amplitude of order unity is close to the value estimated for fluid stars without a crust.
2000
Article
http://edoc.mpg.de/2807
Physical Review D, v.62, 084030 (2000)
en
oai:edoc.mpg.de:28082009-04-026:84
Bulk Witten Indices and the Number of Normalizable Ground States in Supersymmetric Quantum Mechanics of Orthogonal, Symplectic and Exceptional Groups
Staudacher, Matthias
notspecified
This note addresses the question of the number of normalizable vacuum states in supersymmetric quantum mechanics with sixteen supercharges and arbitrary semi-simple compact gauge group, up to rank three. After evaluating certain contour integrals obtained by appropriately adapting BRST deformation techniques we propose novel rational values for the bulk indices. Our results demonstrate that an asymptotic method for obtaining the boundary contribution to the index, originally due to Green and Gutperle, fails for groups other than SU(N). We then obtain likely values for the number of ground states of these systems. In the case of orthogonal and symplectic groups our finding is consistent with recent conjectures of Kac and Smilga, but appears to contradict their result in the case of the
exceptional group G2.
2000
Article
http://edoc.mpg.de/2808
Physics Letters B, v.488, 194-198 (2000)
en
oai:edoc.mpg.de:28092009-03-176:82
Investigations of 3D binary Black Hole Systems
Nerger, Lars
notspecified
Thesis
http://edoc.mpg.de/2809
en
ResultSet_5F0om1ST63r_range_100-199