# The Nineteenth Release of the Einstein Toolkit

Release Announcement

We are pleased to announce the nineteenth release (code name “Mayer”) of the Einstein Toolkit, an open, community developed software infrastructure for relativistic astrophysics. The highlights of this release are:

A new thorn has been added:

* FishboneMoncriefID

Also, for the first time, a new code has been added.

* SelfForce-1D

The ETK is embracing a new model of assigning credit: Until now, the 2012 Einstein Toolkit paper was the common way to cite the Einstein Toolkit (though we suggested citing the website itself). In this release, however, we will begin using https://doi.org/10.5281/zenodo.3522086 to recognize the many contributers that have worked on the toolkit since that time.

In principle, the Einstein Toolkit was always intended to be a collection of codes for exploring numerical relativity, not simply a collection of arrangements and thorns for the Cactus Framework. Going forward, SelfForce-1D will have regular releases using the same release tags as the Cactus-based codes, and will have a similar setup for the running of test-suites. While the new code will not download at the same time as the Cactus-based code, download instructions will appear in the same places.

In addition, bug fixes accumulated since the previous release in March 2019 have been included.

The Einstein Toolkit is a collection of software components and tools for simulating and analyzing general relativistic astrophysical systems that builds on numerous software efforts in the numerical relativity community including the spacetime evolution codes McLachlan and Lean, analysis codes to compute horizon characteristics and gravitational waves, the Carpet AMR infrastructure, and the relativistic magneto-hydrodynamics codes GRHydro and IllinoisGRMHD. For parts of the toolkit, the Cactus Framework is used as the underlying computational infrastructure providing large-scale parallelization, general computational components, and a model for collaborative, portable code development.

The Einstein Toolkit uses a distributed software model and its different modules are developed, distributed, and supported either by the core team of Einstein Toolkit Maintainers, or by individual groups. Where modules are provided by external groups, the Einstein Toolkit Maintainers provide quality control for modules for inclusion in the toolkit and help coordinate support. The Einstein Toolkit Maintainers currently involve postdocs and faculty from six different institutions, and host weekly meetings that are open for anyone to join in.

Guiding principles for the design and implementation of the toolkit include: open, community-driven software development; well thought-out and stable interfaces; separation of physics software from computational science infrastructure; provision of complete working production code; training and education for a new generation of researchers.

For more information about using or contributing to the Einstein Toolkit, or to join the Einstein Toolkit Consortium, please visit our web pages at http://einsteintoolkit.org.

The Einstein Toolkit is primarily supported by NSF 1550551/1550461/1550436/1550514 (Einstein Toolkit Community Integration and Data Exploration).

The Einstein Toolkit contains about 400 regression test cases. On a large portion of the tested machines, almost all of these tests pass, using both MPI and OpenMP parallelization.

The changes between this and the previous release include:

Larger changes since last release

* The Fishbone Moncrief Initial Data thorn (FishboneMoncriefID) thorn has been added to the WVUThorns arrangement
– This thorn solves the equations originally posed by Fishbone & Moncrief, describing a non-self-gravitating equilibrium disk of matter orbiting a spinning black hole in standard (spherical) Kerr-Schild coordinates. When the disk is seeded with initially dynamically unimportant poloidal magnetic fields, dramatic magnetic instabilities occur during the subsequent evolution, launching ultrarelativistic jets. Thus the Fishbone-Moncrief solution provides a standard testbed for GRMHD accretion disk codes.
– From a code perspective, FishboneMoncriefID is notable in that it is the first ETK thorn entirely written and documented within pedagogical Jupyter notebooks. In these notebooks, the Fishbone-Moncrief equations are converted from Einstein-like notation into optimized C code using NRPy+, a Kranc analogue depending only on Python and its open-source SymPy computer algebra software.
* The inclusion of the SelfForce-1D code in the Einstein Toolkit as the first non-Cactus code in the toolkit.
– Evolves the sourced scalar wave equation on a Schwarzschild spacetime using the effective source approach to point particles.
– The wave equation is decomposed into spherical harmonics and the resulting 1+1 dimensional equations are discretized in the radial direction using the discontinuous Galerkin method.
* Update hwloc to 1.11.12
* Groups of vectors of vectors are now handled properly by RotatingSymmetry90 and RotatingSymmetry180
* Compilation of PAPI is faster and produces fewer warnings

How to upgrade from Proca (ET_2019_03)

To upgrade from the previous release, use GetComponents with the new thornlist to check out the new version.

As the SelfForce-1D code was not present in the previous release, there is no need to upgrade. Just follow the download instructions.

Machine notes

Supported (tested) machines include:

* Default Debian, Ubuntu, Fedora, CentOS 7, Mint, OpenSUSE and MacOS Mojave (MacPorts) installations
* Bluewaters
* Comet
* Cori
* Stampede 2
* Mike

* TACC machines: defs.local.ini needs to have sourcebasedir = $WORK and basedir =$SCRATCH/simulations configured for this machine. You need to determine $WORK and$SCRATCH by logging in to the machine.

All repositories participating in this release carry a branch ET_2019_10 marking this release. These release branches will be updated if severe errors are found.

The “Mayer” Release Team on behalf of the Einstein Toolkit Consortium (2019-10-25)

* Steven R. Brandt
* Maria Babiuc-Hamilton
* Peter Diener
* Matthew Elley
* Zachariah Etienne
* Giuseppe Ficarra
* Roland Haas
* Helvi Witek

Oct, 2019

# Inhomogeneous Cosmologies IV, Torun, Poland (2nd announcement)

During 14-19 July 2019 we are gathering experts in inhomogeneous cosmology for a small workshop of about 30 participants at Nicolaus Copernicus University in Torun, the town where Copernicus was born. We wish to map out the most promising directions for analytical, numerical and observational investigations aimed to take into account both structure formation and cosmological expansion within the constraints of general relativity.

Can we clarify the physics present in the relativistic cosmology software now being developed? Are the calculations artificially constrained or are they fully relativistic? Can we achieve accurate postdiction of cosmological observations and follow up by making predictions for the upcoming decade of new major survey projects? We expect vigorous, constructive debate between “one-percenters” and “order-unity” proponents, and practical hands-on sessions of free-licensed inhomogeneous cosmology software packages.

Feel free to redistribute this announcement. The deadline for early registration is **3 May 2019**.

Contact: cosmotorun19 at cosmo.torun.pl

Scientific organising committee: Boud Roukema, Eloisa Bentivegna, Krzysztof Bolejko, Thomas Buchert, Mikolaj Korzynski, Hayley Macpherson, Jan Ostrowski, Sebastian Szybka, Eleonora Villa, David Wiltshire

Local organising committee: Boud Roukema, Justyna Cembrzynska, Agnieszka Gorska-Pukownik, Justyna Borkowska, Matteo Cinus, Marius Peper

Topics will include:
* exact cosmological solutions of the Einstein equations
* averaging and backreaction in cosmology
* numerical cosmological relativity
* observational tests

# The Eighteenth Release of the Einstein Toolkit

The Eighteenth Release of the Einstein Toolkit

We are pleased to announce the eighteenth release (code name “Proca”) of the Einstein Toolkit, an open, community developed software infrastructure for relativistic astrophysics. The highlights of this release are:

New arrangements and thorns have been added:

* Proca

– NPScalars_Proca
– ProcaBase
– ProcaEvolve
– Proca_simpleID
– TwoPunctures_KerrProca

* lean_public

– LeanBSSNMoL
– NPScalars

* wvuthorns_diagnostics

– particle_tracerET
– Seed_Magnetic_Fields_BNS
– smallbPoynET
– VolumeIntegrals_GRMHD
– VolumeIntegrals_vacuum

In addition, bug fixes accumulated since the previous release in September 2018 have been included.

The Einstein Toolkit is a collection of software components and tools for simulating and analyzing general relativistic astrophysical systems that builds on numerous software efforts in the numerical relativity community including CactusEinstein, the Carpet AMR infrastructure and the relativistic magneto-hydrodynamics codes GRHydro and IllinoisGRMHD. For parts of the toolkit, the Cactus Framework is used as the underlying computational infrastructure providing large-scale parallelization, general computational components, and a model for collaborative, portable code development. The toolkit includes modules to build complete codes for simulating black hole spacetimes as well as systems governed by relativistic magneto-hydrodynamics.

The Einstein Toolkit uses a distributed software model and its different modules are developed, distributed, and supported either by the core team of Einstein Toolkit Maintainers, or by individual groups. Where modules are provided by external groups, the Einstein Toolkit Maintainers provide quality control for modules for inclusion in the toolkit and help coordinate support. The Einstein Toolkit Maintainers currently involve postdocs and faculty from six different institutions, and host weekly meetings that are open for anyone to join in.

Guiding principles for the design and implementation of the toolkit include: open, community-driven software development; well thought out and stable interfaces; separation of physics software from computational science infrastructure; provision of complete working production code; training and education for a new generation of researchers.

For more information about using or contributing to the Einstein Toolkit, or to join the Einstein Toolkit Consortium, please visit our web pages at http://einsteintoolkit.org.

The Einstein Toolkit is primarily supported by NSF 1550551/1550461/1550436/1550514 (Einstein Toolkit Community Integration and Data Exploration). The Einstein Toolkit contains about 400 regression test cases. On a large portion of the tested machines, almost all of these tests pass, using both MPI and OpenMP parallelization.

The changes between this and the previous release include:

Larger changes since last release

* The Proca arrangement has been added: This repository provides the tools to evolve the Einstein-Proca system as first described in https://arxiv.org/abs/1505.00797.

– NPScalars_Proca: Implementation of the spin-1 (electromagnetic) and spin-2 (gravitational) Newman-Penrose scalars
– Proca_simpleID: Create analytic initial data for a non-rotating black hole surrounded by a Proca field with mass mu.
– TwoPunctures_KerrProca: A modified TwoPunctures thorn to construct initial data for a single rotating black hole coupled to a massive vector field.

* The Lean arrangement has been added:

– LeanBSSNMoL: Implementation to evolve Einstein’s Equations using the W-version of the BSSN formulation together with the puncture gauge. Also available, in the “new_gauge” branch, is a modified “Gamma- driver” that stabilizes highly rotating black hole spacetimes (adapted from Figueras et al; see: https://arxiv.org/abs/1512.04532).
– NPScalars: Implementation of the spin-2 Newman-Penrose scalars

* The WVU Diagnostics arrangement has been added: These thorns are designed primarily to add useful diagnostics for binary neutron star simulations performed with IllinoisGRMHD.

– NSNS_parameter_files Contains parameter files for magnetized and unmagnetized BNS evolutions.
– Seed_Magnetic_Fields_BNS Extended Seed_Magnetic_Fields thorn for binary neutron stars.
– VolumeIntegrals_GRMHD: GRMHD volume integration thorn, currently depends on IllinoisGRMHD and Carpet. Performs volume integrals on arbitrary “Swiss-cheese”-like topologies, and even interoperates with Carpet to track NS centers of mass.
– VolumeIntegrals_vacuum: Same functionality as VolumeIntegrals_GRMHD, but designed for integration of spacetime quantities. Depends on ML_BSSN and ADMBase for integrands.
– particle_tracerET Solves the ODE \partial_t x^i=v^i for typically thousands of tracer particles, using an RK4 integration atop the current time stepping.
– smallbPoynET Computes b^i, b^2, and three spatial components of Poynting flux. It also computes (-1-u_0), which is useful for tracking unbound matter.

* Ticket tracking system moved to bitbucket: https://bitbucket.org/einsteintoolkit/tickets/
* Subversion infrastructure for thorns is no longer maintained at LSU. Instead, the svn checkout mechanism supported by github.com is used.
* Llama supports tensorweights other than 1.0 or 0.0
* Added EinsteinAnalysis/Hydro_Analysis/Hydro_Analysis_Masses.F90 in order to compute the total baryonic mass and baryonic mass within user defined radii.
* A summary of changes Carpet:

– add support for very large grids where 64bit integer are needed for grid indices and sizes of transfer buffers
– fix how physical_time_per_hour is computed
– add functionality to align interior of grid functions to cache boundaries. This requires changes t. Cactus and PUGH as well.
– add a parameter “granularity” to make sure the interior of components is a multiple of N points in each direction

* The version of MPI bundled with the ET is now OpenMPI 1.10.7
* The SystemTopology thorn now supports hwloc 2.0

How to upgrade from Chien-Shiung Wu (ET_2018_09)

To upgrade from the previous release, use GetComponents with the new thornlist to check out the new version.

Machine notes

Supported (tested) machines include:

* Default Debian, Ubuntu, Fedora, CentOS, Mint, OpenSUSE and MacOS (MacPorts) installations
* Bluewaters
* Comet
* Golub
* Stampede 2
* Shelob
* Wheeler

* TACC machines: defs.local.ini needs to have sourcebasedir=$WORK and basedir=$SCRATCH/simulations configured for this machine. You need to determine $WORK and$SCRATCH by logging in to the machine.

All repositories participating in this release carry a branch ET_2019_03 marking this release. These release branches will be updated if severe errors are found.

The “Proca” Release Team on behalf of the Einstein Toolkit Consortium (2019-03-29)

* Steven R. Brandt
* Samuel D. Cupp
* Peter Diener
* Zachariah Etienne
* Roland Haas
* Helvi Witek

Mar, 2019

# Inhomogeneous Cosmologies IV, Torun, Poland

During 14-19 July 2019 we are gathering experts in inhomogeneous cosmology for a small workshop of about 30 participants at Nicolaus Copernicus University in Torun, the town where Copernicus was born. We wish to map out the most promising directions for analytical, numerical and observational investigations aimed to take into account both structure formation and cosmological expansion within the constraints of general relativity. Can we clarify the physics present in the relativistic cosmology software now being developed? Are the calculations artificially constrained or are they fully relativistic? Can we achieve accurate postdiction of cosmological observations and follow up by making predictions for the upcoming decade of new major survey projects? We expect vigorous, constructive debate between “one-percenters” and “order-unity” proponents, and practical hands-on sessions of free-licensed inhomogeneous cosmology software packages.

Feel free to redistribute this announcement. Check the CosmoTorun19 website or subscribe to the inhom newsletter to know when registration is open.

Contact: cosmotorun19 at cosmo.torun.pl

Organising committee: Boud Roukema, Eloisa Bentivegna, Krzysztof Bolejko, Thomas Buchert, Mikolaj Korzynski, Hayley Macpherson, Jan Ostrowski, Sebastian Szybka, Eleonora Villa, David Wiltshire

Topics will include:
* exact cosmological solutions of the Einstein equations
* averaging and backreaction in cosmology
* numerical cosmological relativity
* observational tests

# PhD positions in numerical relativity/cosmology at Center for Theoretical Physics, Polish Academy of Science

The Director of the Center for Theoretical Physics PAS invites applications for 2 PhD positions at the CTP PAS, financed from the project “Local relativistic perturbation theory in hydrodynamics and cosmology”. The principal investigator is Prof. Mikolaj Korzynski. The positions start on 1st September 2017, and will last until the end of the project (46 months). The PhD students will be enlisted as a participants of the PhD Program of the Institute of Physics PAS, following their individual programs. The subject of the PhD will be related to the topic of the project. The students will receive a stipend of 3000 zl/month.

The group of Mikolaj Korzynski will work on the application of numerical relativity to cosmology, especially the problems of structure formation and the light propagation through spacetime, combining numerics, stochastic and perturbative methods.

At the time of application the candidates should either have a MSc degree, or expect to obtain it before signing the contract. The positions require a MSc or compatible in physics, astronomy, computer science or related field. Experience in any of the following: general relativity, astrophysics, differential geometry, computational hydrodynamics would be an advantage, although is not necessary. The tasks of the PhD students involve investigation of structure formation in the Universe using numerical simulations and perturbative approach.

The applicants should submit the following documents:
1. scientific CV, including the major scientific achievements, list of publications, participation in research projects and conferences. The document should contain the statement: “I hereby give consent to the processing of my personal data for the needs of the recruitment process (in accordance with the Law dated 29.08.97 on the protection of personal data (Journal of Laws, No. 101, item 926)”.
2. transcript of records from undergraduate studies
3. personal questionnaire form from the CTP PAS webpage
4. certified copy of the MSc diploma (or the letter from the supervisor about the prospects for completion of the Thesis before the beginning of the employment) via email directly to Mikolaj Korzynski (korzynski[AT]cft.edu.pl). Additionally they should arrange for two letters of recommendation to be sent to the same email address.

The deadline for applications is 30th June 2017. Selected applicants will be invited for an interview. For more information please contact Prof. Mikolaj Korzynski (korzynski[AT]cft.edu.pl).

# Postdoc position in numerical relativity/cosmology at Center for Theoretical Physics, Polish Academy of Science

The Director of the Center for Theoretical Physics invites applications for a postdoctoral position at the CTP PAS, financed from the project “Local relativistic perturbation theory in hydrodynamics and cosmology” No. 2016/22/E/ST9/00578 (SONATA BIS 6) supported by the National Science Center, decision No. DEC-2016/22/E/ST9/00578. The principal investigator is Prof. Mikolaj Korzynski. The position starts on September 1st, 2017.

The position requires a PhD in theoretical or computational physics and experience in numerical relativity, computational hydrodynamics, MHD or compatible field. A background in astrophysics, general relativity or cosmology and experience with the EinsteinToolkit framework would be an advantage.

The group of Mikolaj Korzynski will work on the application of numerical relativity to cosmology, especially the problems of structure formation and the light propagation through spacetime, combining numerics, stochastic and perturbative methods.

The applicants should submit the following documents:
1. cover letter including the statement „I hereby give consent for my personal data included in the job offer to be processed for the purposes of recruitment under the Data Protection Act 1997 (Dz. U. no. 101, item 926)”
2. a scientific CV, including the list of publications and major scientific achievements
3. brief description of research interests
4. copy of the PhD diplomma
5. personal questionnaire form from the CTP PAS webpage via email directly to Mikolaj Korzynski (korzynski[AT]cft.edu.pl). Additionally they should arrange for two letters of recommendation to be sent to the same email address. Applicants expecting to obtain their PhD soon should also include a statement from their supervisors about the scheduled date of their defence.

The deadline for applications has been extended to 1st August 2017. Selected applicants will be invited for an interview. Successful applicant will be employed for the trial period of 12 months, with the possibility of extension for up to 3 further years.

# Inhomogeneous Cosmologies (2nd announcement), Torun, Poland

During 2-7 July 2017 we are gathering experts in inhomogeneous cosmology for a small workshop of about 30 participants at Nicolaus Copernicus University in Torun, the town where Copernicus was born. We wish to map out the most promising directions for analytical, numerical and observational investigations aimed to take into account both structure formation and cosmological expansion within the constraints of general relativity. A key motivating theme will be to discuss the claim, already investigated in numerous peer-reviewed papers, that “dark energy” as inferred from observations is an artefact of assuming an average Friedmannian expansion. New techniques in numerical relativity are beginning to open new perspectives on these questions. We expect talks on the latest developments, vigorous, constructive debate between “one-percenters” and “order-unity” proponents, and practical hands-on tutorials of the Einstein Toolkit and other free-licensed inhomogeneous cosmology software packages. The workshop sessions will start on the morning of Mon 3 July and continue to late afternoon Fri 7 July.

Due to the limited number of places available, registration by the early registration deadline of 7 April 2017, including a draft abstract, is strongly recommended. If places remain available, late registration will remain open until the late registration deadline of 9 June 2017 – see http://cosmo.torun.pl/CosmoTorun17 for details.

Contact: cosmotorun17 at cosmo.torun.pl

Organising committee: Boud Roukema, Eloisa Bentivegna, Krzysztof Bolejko, Thomas Buchert, Mikolaj Korzynski, Hayley MacPherson, Jan Ostrowski, Sebastian Szybka, David Wiltshire

Topics will include:

* exact cosmological solutions of the Einstein equations
* averaging and backreaction in cosmology
* numerical cosmological relativity
* observational tests

# Inhomogeneous Cosmologies (1st announcement), Torun, Poland

During 2-7 July 2017 we are gathering experts in inhomogeneous cosmology for a small workshop of about 30 participants at Nicolaus Copernicus University in Torun, the town where Copernicus was born. We wish to map out the most promising directions for analytical, numerical and observational investigations aimed to take into account both structure formation and cosmological expansion within the constraints of general relativity. A key motivating theme will be to discuss the claim, already investigated in numerous peer-reviewed papers, that “dark energy” as inferred from observations is an artefact of assuming an average Friedmannian expansion. New techniques in numerical relativity are beginning to open new perspectives on these questions. We expect vigorous, constructive debate between “one-percenters” and “order-unity” proponents, and practical hands-on sessions of free-licensed inhomogeneous cosmology
software packages.

We will post a formal announcement and registration details by early 2017 at http://cosmo.torun.pl/CosmoTorun17.

Contact: cosmotorun17 at cosmo.torun.pl

Organising committee: Boud Roukema, Thomas Buchert, Krzysztof Bolejko, Mikolaj Korzynski, Jan Ostrowski, Sebastian Szybka, David Wiltshire

# SimulationTools for Mathematica

15th August 2013

We present “SimulationTools for Mathematica” (http://simulationtools.org/), available as free software under the GNU General Public License. SimulationTools is a Mathematica application for analysing data from numerical simulations. It has a modular design applicable to general grid-based numerical simulations, and contains specific support for the Cactus code, with a focus on the field of Numerical Relativity and the Einstein Toolkit.

SimulationTools provides a functional, programmable interface to simulation data. A highly-optimised HDF5 module can be used for reading HDF5 data from production simulations, including 1D, 2D and 3D grid data produced by the Carpet code. Simulation details such as filenames, file formats, and details of parallel I/O are hidden from the user.

Numeric data with attached coordinate information is manipulated using new data types. Many useful new functions are defined on these types, and most built-in numerical Mathematica functions such as +, -, *, /, Abs, Sin, Log and Max can be used transparently. There is also support for testing numerical convergence, with automatic resampling onto a common grid if desired.

SimulationTools has generic functionality useful for analysis of many types of data, as well as explicit support for codes including Cactus, Carpet, Llama, SimFactory and many other components of the Einstein Toolkit. It provides an overview of the state of a simulation, including speed, memory usage, and physics (e.g. trajectories and waveforms from a binary system). The design is modular, and support for output from other codes can be added.

Specific functionality for Numerical Relativity is available. Gravitational waveforms can be read from simulations using natural function semantics, and the waveforms can be manipulated, for example converting between Psi4 and strain and extrapolation to infinity. An abstraction for “binary systems” provides a convenient interface to the trajectories of members of a binary system tracked with codes from the Einstein Toolkit. Support for reading black hole masses and spins is also included. Data in the Numerical Relativity Data Format (as used in the NINJA and NR-AR projects) can be read using the same functions that are used for normal simulation data.

More details are available on the SimulationTools website (http://simulationtools.org), including an extensive feature summary, a list of capabilities and online documentation (http://simulationtools.org/Documentation/English/Tutorials/SimulationTools.html). Tutorials and reference documentation are also available within the standard Mathematica documentation system. Code quality is maintained to a high standard with ~400 unit tests.

SimulationTools has been in production use for over 5 years and has been used at several research institutions worldwide. We invite you to try out the code (http://simulationtools.org/download), join the mailing list (http://simulationtools.org/mailman/listinfo/users) and freely use SimulationTools for your research.

Ian Hinder and Barry Wardell
http://numrel.aei.mpg.de/people/hinder
http://barrywardell.net/

# SimulationTools for Mathematica

15th August 2013

We present “SimulationTools for Mathematica” <http://simulationtools.org/>, available as free software under the GNU General Public License. SimulationTools is a Mathematica application for analysing data from numerical simulations. It has a modular design applicable to general grid-based numerical simulations, and contains specific support for the Cactus code, with a focus on the field of Numerical Relativity and the Einstein Toolkit.

SimulationTools provides a functional, programmable interface to simulation data. A highly-optimised HDF5 module can be used for reading HDF5 data from production simulations, including 1D, 2D and 3D grid data produced by the Carpet code. Simulation details such as filenames, file formats, and details of parallel I/O are hidden from the user.

Numeric data with attached coordinate information is manipulated using new data types. Many useful new functions are defined on these types, and most built-in numerical Mathematica functions such as +, -, *, /, Abs, Sin, Log and Max can be used transparently. There is also support for testing numerical convergence, with automatic resampling onto a common grid if desired.

SimulationTools has generic functionality useful for analysis of many types of data, as well as explicit support for codes including Cactus, Carpet, Llama, SimFactory and many other components of the Einstein Toolkit. It provides an overview of the state of a simulation, including speed, memory usage, and physics (e.g. trajectories and waveforms from a binary system). The design is modular, and support for output from other codes can be added.

Specific functionality for Numerical Relativity is available. Gravitational waveforms can be read from simulations using natural function semantics, and the waveforms can be manipulated, for example converting between Psi4 and strain and extrapolation to infinity. An abstraction for “binary systems” provides a convenient interface to the trajectories of members of a binary system tracked with codes from the Einstein Toolkit. Support for reading black hole masses and spins is also included. Data in the Numerical Relativity Data Format (as used in the NINJA and NR-AR projects) can be read using the same functions that are used for normal simulation data.

More details are available on the SimulationTools website <http://simulationtools.org>, including an extensive feature summary, a list of capabilities and online documentation <http://simulationtools.org/Documentation/English/Tutorials/SimulationTools.html>. Tutorials and reference documentation are also available within the standard Mathematica documentation system. Code quality is maintained to a high standard with ~400 unit tests.

SimulationTools has been in production use for over 5 years and has been used at several research institutions worldwide. We invite you to try out the code  <http://simulationtools.org/download>, join the mailing list <http://simulationtools.org/mailman/listinfo/users> and freely use SimulationTools for your research.

Ian Hinder and Barry Wardell
http://numrel.aei.mpg.de/people/hinder
http://barrywardell.net/

# Llama Multi-Block Infrastructure publicly available

http://llamacode.org/

The Llama Multi-Block Infrastructure for Cactus is now publicly available under the GNU General Public License. Llama provides three-dimensional multi-block capability for Cactus-based simulations that can be combined with Carpet’s adaptive mesh refinement functionality. Llama decomposes the domain into multiple (potentially overlapping) blocks with different local coordinate systems. This allows e.g. spherical domains, spherical excision, adaptive radial/angular resolution, etc., without incurring coordinate singularities.

Llama provides several patch systems suitable for single and binary objects in relativistic astrophysics, and is well integrated with the Einstein Toolkit . Llama was already used for several publications , and we believe the code is ready to be used in other projects. We are seeking volunteers to help us add tutorials and documentation, improve error messages, and generally shake down and brush up the code for a future inclusion in the Einstein Toolkit.

To aid others in getting started using Llama, we will be hosting a virtual workshop where we provide an overview of the code and answer questions. Details will be announced shortly.

Llama constitutes the fruit of a significant effort of several people over several years. We make Llama public to help modernize the computational tools used in our community, and in the hope to boost Llama itself by inviting contributions from everybody. We ask you to acknowledge our effort by following the citation guidelines described on .

The Llama groomers:

R. Haas, I. Hinder, D. Pollney, C. Reisswig, E. Schnetter, B. Wardell

# New book: “3+1 Formalism in General Relativity” by Eric Gourgoulhon

3+1 Formalism in General Relativity: Bases of Numerical Relativity

Eric Gourgoulhon
Springer, 2012
294 pages

Contents:
1. Introduction
2. Basic Differential Geometry
3. Geometry of Hypersurfaces
4. Geometry of Foliations
5. 3+1 Decomposition of Einstein Equation
6. 3+1 Equations for Matter and Electromagnetic Field
7. Conformal Decomposition
8. Asymptotic Flatness and Global Quantities
9. The Initial Data Problem
10. Choice of Foliation and Spatial Coordinates
11. Evolution Schemes
A. Conformal Killing Operator and Conformal Vector Laplacian
B. Sage Codes

More details at http://relativite.obspm.fr/3p1

# Einstein Toolkit Release

We are pleased to announce the second release (code name “Chandrasekhar”) of the Einstein Toolkit, an open, community developed software infrastructure for relativistic astrophysics. This release is mainly a maintenance release incorporating fixes accumulated since the previous release in June 2010, as well as additional test suites.

The Einstein Toolkit is a collection of software components and tools for simulating and analyzing general relativistic astrophysical systems that builds on numerous software efforts in the numerical relativity community including CactusEinstein, the Carpet AMR infrastructure and on the public version of the Whisky hydrodynamics code (now modified and called GRHydro). The Cactus Framework is used as the underlying computational infrastructure providing large-scale parallelization, general computational components, and a model for collaborative, portable code development. The toolkit includes modules to build complete codes for simulating black hole spacetimes as well as systems governed by relativistic hydrodynamics. Current development in the consortium is targeted at providing additional infrastructure for general relativistic magnetohydrodynamics.

The Einstein Toolkit uses a distributed software model and its different modules are developed, distributed, and supported either by the core team of Einstein Toolkit Maintainers, or by individual groups. Where modules are provided by external groups, the Einstein Toolkit Maintainers provide quality control for modules for inclusion in the toolkit and help coordinate support. The Einstein Toolkit Maintainers currently involve postdocs and faculty from five different institutions, and host weekly meetings that are open for anyone to join in.

Guiding principles for the design and implementation of the toolkit include: open, community-driven software development; well thought out and stable interfaces; separation of physics software from computational science infrastructure; provision of complete working production code; training and education for a new generation of researchers.

For more information about using or contributing to the Einstein Toolkit, or to join the Einstein Toolkit Consortium, please visit our web pages http://einsteintoolkit.org.

The Einstein Toolkit is primarily supported by NSF 0903973/0903782/0904015 (CIGR), and also by NSF 0701566/0855892 (XiRel), 0721915 (Alpaca), 0905046/0941653 (PetaCactus) and 0710874 (LONI Grid).

The “Chandrasekhar” Release Team on behalf of the Einstein Toolkit Consortium (2010-11-23)

# Numerical Relativity: Solving Einstein’s Equations on the Computer (New Book)

Numerical Relativity: Solving Einstein’s Equations on the Computer

T. W. Baumgarte and S. L. Shapiro
Cambridge University Press, 2010

Aimed at students and researchers entering the field, this pedagogical introduction to numerical relativity will also interest scientists seeking a broad survey of its challenges and achievements. Assuming only a basic knowledge of classical general relativity, this textbook develops the mathematical formalism from first principles, then highlights some of the pioneering simulations involving black holes and neutron stars, gravitational collapse and gravitational waves. Applications include calculations of coalescing binary black holes and binary neutron stars, rotating stars, colliding star clusters, gravitational and magnetorotational collapse, critical phenomena, the generation of gravitational waves, and many more.

Features of the book include:

– 300 exercises help readers master new material as it is presented.

– Numerous illustrations, many in color, assist in visualizing new geometric concepts and highlighting the results of computer simulations.

– Summary boxes encapsulate some of the most important results for quick reference.

– Applications cover topics of current physical and astrophysical significance.

For details, see http://www.cambridge.org/us/knowledge/isbn/item2707919/?site_locale=en_US

# Einstein Toolkit Release

We are pleased to announce the first release (code name “Bohr”) of the Einstein Toolkit, an open, community developed software infrastructure for relativistic astrophysics. The Einstein Toolkit is a collection of over 130 software components and tools for simulating and analyzing general relativistic astrophysical systems that builds on numerous software efforts in the numerical relativity community including CactusEinstein, the Whisky hydrodynamics code, and the Carpet AMR infrastructure. The Cactus Framework is used as the underlying computational infrastructure providing large-scale parallelization, general computational components, and a model for collaborative, portable code development. The toolkit includes modules to build complete codes for simulating black hole spacetimes as well as systems governed by relativistic hydrodynamics. Current development in the consortium is targeted at providing additional infrastructure for general relativistic magnetohydrodynamics.

The Einstein Toolkit uses a distributed software model and its different modules are developed, distributed, and supported either by the core team of Einstein Toolkit Maintainers, or by individual groups. Where modules are provided by external groups, the Einstein Toolkit Maintainers provide quality control for modules for inclusion in the toolkit and help coordinate support. The Einstein Toolkit Maintainers currently involve postdocs and faculty from five different institutions, and hold weekly meetings that are open for anyone to join in.

Guiding principles for the design and implementation of the toolkit include:

1: Open, community-driven software development that encourages the sharing of code across the community, prevents code duplication, and leads to sustainable support and development of essential code.

2: Well thought out and stable interfaces between components that enable multiple implementations of physics capabilities, and allow groups or individuals to concentrate on their areas of interest.

3: Separation of physics software from computational science infrastructure so that new technologies for large scale computing, processor accelerators, or parallel I/O can be easily integrated with science codes.

4: The provision of complete working production codes to provide: prototypes, standard benchmarks, and testcases; codes that are available for and usable by the general astrophysics community; tools for new researchers and groups to enter this field; training and education for a new generation of researchers.

For more information about using or contributing to the Einstein Toolkit, or to join the Einstein Toolkit Consortium, please visit our web pages at <http://einsteintoolkit.org>.

We thank the numerous people who contributed to this software over the past many years; there are too many to be listed here. We also gratefully acknowledge those who helped in the past months to make this release happen. The Einstein Toolkit is primarily supported by NSF 0903973/0903782/0904015 (CIGR), and also by NSF 0701566/0855892 (XiRel), 0721915 (Alpaca), 0725070 (Blue Waters), and 0905046/0941653 (PetaCactus).

The “Bohr” Release Team on behalf of the Einstein Toolkit Consortium
(2010-06-17)

# NRDA09/MICRA09 Double special issue published in Classical and Quantum Gravity

I am delighted to announce the publication of the following double special issue in Classical and Quantum Gravity:

Invited papers from Numerical Relativity and Data Analysis (NRDA) 2009,
Albert Einstein Institute, Potsdam, 6 – 9 July, 2009
Guest Editors: S Husa and B Krishnan

Invited papers from Microphysics In Computational Relativistic Astrophysics (MICRA) 2009,
Niels Bohr International Academy, Copenhagen, 24 – 28 August 2009
Guest Editors: C D Ott, C Pethick and L Rezzolla

The NRDA meeting was aimed at fostering closer interactions between simulations of gravitational wave sources and the ongoing searches for gravitational wave signals.

The MICRA meeting brought together researchers in numerical modeling and physics of matter at high densities, where general relativity plays a central role.

I take this opportunity to thank all of the authors, referees and guest editors who gave their time and expertise to create this excellent issue.

The special issue will be free for 6 months from date of publication. I invite you to read the articles on the new IOPscience service!

Yours sincerely,

Publisher
Classical and Quantum Gravity
iopscience.org/cqg

# Workshop on Unstructured Meshes in Dynamical Spacetimes

We are pleased to announce the Workshop on Unstructured Meshes in Dynamical Spacetimes in Jena, Germany on 25-27 August 2010.

This workshop on the use of unstructured meshes in numerical relativity has been devised as a means to bring together experts in numerical relativity, finite elements, finite volumes, discrete differential forms, and Regge calculus to encourage discussion between the communities and identify areas in which new progress can be made.

Topics for talks and discussions will be aimed at
-Finite element methods in numerical relativity
-Dynamical space-time meshing
-Applications for finite-volume methods
-Higher order geometric discretizations of Einstein’s equations
-Numerical methods based on Regge calculus
-Advances in discrete differential forms.

Registration is currently open, and we are accepting contributed talks. The deadline for submission of abstracts is 31 July 2010.

http://cse.mathe.uni-jena.de/wumds/

Sincerely,
Snorre H. Christiansen (University of Oslo)
Jonathan R. McDonald (Friedrich Schiller University, Jena)
Warner A. Miller (Florida Atlantic University, Boca Raton)
Gerhard Zumbusch (Friedrich Schiller University, Jena)