March 2002

On march 2002 for the LSC meeting we gathered the status of (some of) the different groups working on the full simulation side. The collected material (relevant to the BH/BH problem) follows (in no particular order). NOTE: 'group names' are to be taken lightly as a number of  people have moved, thus these names reflect mainly where most of the work took place rather than the people involved (though the representative publications will give you an idea on this):

• UIUC-Bowdoin-Japan
• PSU
• Caltech-Cornell
• AEI-UNAM-UT Brownsville
• LSU
• Texas
• UBC
• Pitt
• Nasa-AEI

UIUC-Bowdoin-Japan

Employing a BSSN code (free evolution, using Finite Differences). Working on different topics of BH/BH simulations (excision, boundary conditions) though considerable work has gone into the NS/NS problem (seee eg 1). Beyond its relevance to the NS/NS problem, work on this system serve as a `test' of the code performance as for the GR part is the same as that used for the BH/BH case (see eg 2,3). Additionally, it has been invested excision strategies (see 3)

1. Hydrodynamic Simulations in 3+1 General Relativity (gr-qc/0209102)
2. Improved numerical stability of stationary black hole evolution calculations (gr-qc/0209102)
3. A numerical testbed for singularity excision in moving black hole spacetimes (gr-qc/0109032)

PSU

Employing a BSSN code (free evolution, using Finite Differences). Working on different topics of BH/BH simulations, (excision, initial data, gauge and outer boundary conditions) and implementation of `isolated horizons' to extract physical information (eg. 2). Studying moving black holes and variants of BSSN for improved stability (eg. 1).

1. Numerical stability of a new conformal-traceless 3+1 formulation of the Einstein equation (gr-qc/0202105)
2. Introduction to Isolated Horizons in Numerical Relativity (gr-qc/0206008)

Caltech-Cornell

Employing a symmetric-hyperbolic code (free evolution, using pseudo-spectral methods). Working on different topics. Especially initial data (eg. 3), evolutions (eg. 1), boundary conditions and variants of formulations. In this latter case, study of methods to 'predict' which variant might be better for a given problem (eg. 2). On going work on binary black holes.

1. Toward stable 3D numerical evolutions of black-hole spacetimes (gr-qc/0209115)
2. Energy Norms and the Stability of the Einstein Evolution Equations (gr-qc/0206035)
3. A multidomain spectral method for solving elliptic equations (gr-qc/0202096)

AEI-UNAM-UT Brownsville

Employing a BSSN code (free evolution, using Finite Differences). Working on binary black holes and distorted black holes. (Also non-vacuum evolutions being simulated with this code). Examining excision strategies, initial data and coordinate conditions. Work on coordinates conditions to maintain holes at 'fixed' coordinate locations. PN data being investigated as seed for initial data problem (eg. 3) and perturbation around single black holes for the late stages (eg. 4). Further developments in cactus being pursued: Grid, FMR & AMR among other things. A few related publications..

1. Gauge conditions for long-term numerical black hole evolutions without excision (gr-qc/0206072)
2. Black Hole Excision for Dynamic Black Holes (gr-qc/0104020)
3. Binary black hole initial data for numerical general relativity based on post-Newtonian data (gr-qc/0207011)
4. The Lazarus project: A pragmatic approach to binary black hole evolutions (gr-qc/0104063)

LSU

Starting a symmetric hyperbolic code (free evolution, using Finite Differences). Building it from `bottom-up'. Stragey for removing `standard' problems: Ensure a discrete energy bound exists (to ensure control of the solution) and implementing constraint preserving boundary conditions (eg. 1,3). Systematic build up guaranteeing each step preserve the energy bound. Investigation of gauge conditions (eg. 2)

1. Well posed constraint-preserving boundary conditions for the linearized Einstein equations (gr-qc/0209017)
2. Exploiting gauge and constraint freedom in hyperbolic formulations of Einstein's equations (gr-qc/0205086)
3. Constraint-preserving boundary conditions in numerical relativity (gr-qc/0205086)

Texas

Working on initial data setting and the physical content. Event horizon locators and formulations (free evolution, using finite differences).

UBC-LIU-BYU

Implementing (fully/partially constrained, using Finite Differences) 2D code. Aggressively pursuing AMR & coordinate conditions (2,3). Compactified slices to get rid of boundary conditions implemented in 2D (1).

1. The final fate of the black string (to be submitted)
2. The Singularity Threshold of the Nonlinear Sigma Model Using 3D Adaptive Mesh Refinement (gr-qc/0202093)
3. Critical phenomena in 2D... (not exact title) [to be submitted]

Pittsburgh

Implementing a symmetric hyperbolic code in harmonic coordinates (using Finite Differences). Work on constraint preserving (minimally dissipative) boundary conditions (1,2). Incorporating the gained knowledge in Cauchy-characteristic matching implementation (2).

1. Well-Posed Initial-Boundary Evolution in General Relativity (gr-qc/0205044)
2. Boundary conditions in linearized harmonic gravity (gr-qc/0106026)

NASA

[go back up]

Using a BSSN code (free evolutions, using Finite Differences). AMR implementation using PARAMESH. Collaborations in the Lazarus project with UT-Brownsville-AEI.